Monthly Archives: May 2023

Which DIY mold test kit should I get?

Which DIY mold test kit should I get?

Every home has some mold, because mold spores practically hitchhike into the home on our clothing, groceries, and even the air.  The difference between acceptable levels of mold and an infestation, however, is whether the moisture and food sources exist to feed an infestation.  There are many reasons to test your home for unacceptable levels of mold, some of which are:

  • Musty smells in an area

  • Recent flooding in or around your home

  • Roof damage

  • Renovations like roof, siding or foundation repair that expose your home to the elements

  • Mysterious health issues in any resident of your home

If you suspect an infestation of mold in your home, there’s no time to waste in testing, stopping the growth and removing the mold!  The health effects of living with a mold infestation are too costly not to do anything! 

Of course, if you have the resources and are able to hire a trained, reputable mold inspection and remediation company, they are often preferable to DIY kits because these inspectors have the training and equipment to make a thorough inspection and testing of your home.  However, working on a budget often means if you spend too much on inspection, there isn’t enough money to make a thorough remediation.  We get it, and so do makers of DIY mold testing kits.  For this reason, we have investigated some DIY kits and even partnered with one. 

There are several types of DIY mold testing you can do in your home.  Here is a description of each, from lowest to highest costs:

  • Gravity plates (also commonly called petri dishes)--an Air Sampling method:  When opening a sealed petri dish to the air in your home, mold spores in the air land on the sugar coating (agar) lining the dish and start to grow.  This method does grow mold!  However, unless you get your samples analyzed by a lab, you will not know for sure what species of mold is present, and even then, only “relative” quantities of mold colonies can be inferred.  If you decide to go this route, we recommend Micro Balance Health Products’ EC3 Mold Screening Test Kit - 6 Pack, which retails for $36.  It has detailed, easy to follow instructions to determine a relative “mold burden” in your home, but does not include the option to have your samples analyzed by a lab.  Because it’s sold by a company that has developed several mold abatement products and  many more highly reviewed health supplement products, you can be sure that they are interested in your best health!

  • Spore traps–an Air Sampling Method: GotMold combines the best of professional technology with DIY convenience.  Although it’s a major step-up in pricing from agar plates (a 3-room kit is $299 including return shipping and analysis), you can use the same sampling procedure that professionals use, and professional lab analysis is included in that package.  Their patented BioVac™ Air Sampler can be reused, so if you decide you’d like to retest after completing renovations to make sure the mold is gone (wise idea), you can get refill “cassettes” to use with your machine (again, postage and analysis is included in the cost of the cassettes).  In the lab report, each area tested will be grouped under the following severity of mold: 

    • GREEN — Not Evident

    • YELLOW — Slightly Evident

    • ORANGE — Moderately Evident

    • RED — Significantly Evident

Then, you’ll get spore counts from 4 common and 14 other types of mold, as well as an indication of whether these molds are usually found with water damage.  It gives “next step” recommendations in the conclusion of the report.

  • Immunolytics’ Kit–Combination Air and Swab sampling method: Since not all types of mold reveal themselves in an air sample, Immunolytics offers a Quickstart Kit ($198) made up of gravity plates and 1 swab or “Build Your Own” kit ($33 per sample) that combines the two methods. Like Micro Balance Health Products’ kit, gravity plates are interpreted by number of colonies formed, and swab samples give a percentage of specific molds found in the sample.  You can also ask for a consultation to determine the next steps for your home. 

  • EMMA–Air or Swab sampling method:  Offered by RealTime Labs, This method is VERY simple in that you use the provided swabs or gauze, or cut out a section of your home’s AC filter.  The separate samples can be combined into 1 sample, or charged as separate samples. This test is ideal for homeowners who are already experiencing mold-related illness symptoms, as their “combo” tests not only test your home for 12 of the most common molds, but also detect 5 of the most common mycotoxins (mycotoxins are responsible for illness).  Knowing the mycotoxins floating around your home may help you develop a treatment plan with your doctor, and the company also offers urine tests, pet tests, and tests for other known toxins.  One disadvantage of this method is that combination of samples will not allow you to learn where the mold is coming from (which room has the highest count).  Check out our article “What’s the Difference between EMMA and ERMI?” to learn more about EMMA.  

  • HERTSMI-2–Dust sampling method:  ERMI was a test developed for research purposes by the US government.  Although it can tell you the presence of specific molds, it is unreliable for determining whether a building is safe to re-enter after remediation.  HERTSMI-2 is a method of interpreting the results of ERMI that is much more reliable (for mold scores less than 10) of whether you will get sick again when returning to a water-damaged building (WDB). HERTSMI-2 analyzes the results for 5 specific molds, also called the “Big 5”, which are most likely to cause relapse of symptoms for patients.  EnvironBiomics offers a very reasonable price ($130) and fast service for HERTSMI-2.  They also offer separate tests for endotoxins (bacterial toxins) and actino microbes (gram-positive bacteria), which are not common to be tested (see our article here about endo-and exotoxins).  If your home was heavily water-damaged or had water damage in multiple areas, you may want to opt for a HERTSMI-2 to make sure it’s safe to inhabit after the remediation.

Since the unconditioned outdoors has its own mold biome, it’s a  helpful baseline to reference.  Most tests do not suggest taking an outdoor sample, but GotMold includes one air cassette specifically for the outdoors in each of their kits.  That way, you can see the types and concentrations of mold directly outside your home, which may be influencing your indoor scores.  We have chosen to partner with this company because of the owner’s passion for helping average homeowners detect mold in an economical way (read his personal story and the company’s philosophy here).  Their air sampler was one of the first affordable machines for DIY air sampling.   

Of course, there are many more test kits out there, but be sure to do your research!  Some have extra fees for lab analysis, postage, or consultation, and each lab report reveals different information.  Companies started by physicians (like Realtime Lab or are even more helpful because they have taken the time to screen and affiliate with doctors around the US who can physically treat homeowners and their families who have been affected by mold.  Whichever method you choose, don’t stop looking for the source of mold in your home and remediation of the damage until retesting comes back with an acceptable score.  Even then, “acceptable” to one person may cause relapse in someone whose health has been severely impacted by mold.   Mold can be sneaky and hard to find, so if DIY tests don’t reveal the problem, check out our articles on Taking our Homes Back from Mold and article on How to Choose a Mold Remediation Contractor (which also speaks about inspection) to partner with professionals.  We at HypoAir are also available to help with products that can help keep mold at bay while you're remediating or on a maintenance basis. 

How does the amount of oxygen in the air affect us?

How does the amount of oxygen in the air affect us?

We mostly take air for granted.   It’s a (boring) mixture of 78 percent nitrogen and 20.9 percent oxygen with small amounts of other gasses such as carbon dioxide, neon, and hydrogen.  (10 Interesting Things About Air)  Even though the news headlines seem to revolve around increasing carbon dioxide, let’s look at the gas humans are most in need of: oxygen.

The majority of the world’s oxygen levels are the same: 20.9% if the humidity is 0%.  Water vapor in the air displaces oxygen, and oxygen can go down to 20.1% if the relative humidity is 100%.  This holds true at sea level and high altitude, where the air is said to be “thinner”.  At high altitude, the percentage of oxygen in the air is the same, 20.9%.  However, lower pressure of the atmosphere causes all molecules of air to spread out. That means you get less oxygen in every breath you take, compared to sea level.  (Living in Thin Air)

According to scientists, oxygen levels in the atmosphere in prehistoric times averaged around 30% to 35%, compared to only 21% today – and that the levels are even less in densely populated, polluted city centers and industrial complexes, perhaps only 15 % or lower. (The Oxygen Crisis)  Fifteen percent sounds extreme, first of all because OSHA has defined atmospheric oxygen concentration below 19.5 percent to be unsafe.  We can only take 19.5% as a guideline, because oxygen in our blood is measured in partial pressure, which may vary slightly according to altitude and the CO2 our bodies are attempting to expel.   In general when figuring in humidity, there’s a margin between normal and unsafe of only 1.3%!   And, in populated areas, this margin is getting even smaller.   

A 2021 study showed that oxygen deficiency can happen in large cities due to a number of factors: increased combustion in vehicles and factories consuming oxygen, lack of green space restricting oxygen production or replenishment, and stalling weather patterns that can stop the flow of fresh air into the city.  The study correlated 391 global large cities (with a population of more than 1 million people) using the oxygen index (OI), which is the ratio of oxygen consumption to oxygen production. Results showed that the global urban areas, occupying only 3.8% of the global land surface, accounted for 39% (14.3 ± 1.5 Gt/yr) of the global terrestrial oxygen consumption during 2001−2015. It was estimated that 75% of cities with a population more than 5 million had an OI of greater than 100. Also, cities with larger OI values were correlated with more frequent heatwaves and severe water withdrawals.  In fact, oxygen in large cities has been declining by 4 ppm per year since the 1980’s, and that rate is actually accelerating. 

When the oxygen in air gets too low, as in high altitudes or confined spaces, the body can enter a state of hypoxia, where low levels of oxygen in your body tissues causes symptoms like confusion, restlessness, difficulty breathing, rapid heart rate, and bluish skin.  (Hypoxia)  Unfortunately, many people in mountainous regions around the world suffer from hypoxia and other effects of high-altitude, which are together called Chronic Mountain Sickness (CMS).

To restore proper tissue function, you’ve got to get more oxygen.  Getting more oxygen in your lungs has a long-recognized stimulant effect, allowing you to focus, concentrate and generally perform better mentally.  In your lungs, more oxygen causes the blood vessels in your lungs to dilate, which improves cleansing and tissue repair within them, and helps them exchange gasses more easily.  In the rest of your body, more oxygen lowers blood pressure and heart rate (your heart doesn’t have to pump as much blood to get the correct amount of oxygen), your tissues heal faster, and digestion is improved. (Surprising Health Benefits of Getting Fresh Air)

Whether it’s increasing levels of carbon dioxide (check our article here) or decreasing levels of oxygen, our bodies are not made to live in cities or houses without adequate ventilation!  Ventilation restores oxygen levels to a safe level above 20% and flushes out harmful gasses like carbon dioxide, radon and VOCs.  It’s interesting to note the differences between fresh air and exhaled air:

Fresh Air

Exhaled Air







Other gases



Carbon dioxide 



(The composition of inhaled and exhaled air. What should and shouldn’t contain?)

A note on rescue breathing: although 17% oxygen is less than the OSHA safety minimum of 19.5%, it is more oxygen than unconscious victims who are not breathing are getting (0%), so rescue breathing does help to save lives.  The problem is that anytime we are conscious (breathing on our own), we should be getting oxygen levels at close to fresh air levels (21%)! 

Unless you live in a major city during a heat wave as described above, low oxygen levels in our air at home shouldn’t be a cause for worry.   Why?  Because even if you lived in a sealed room for 12 days, you would die of carbon dioxide poisoning before running out of oxygen.  Thus, carbon dioxide levels are the greater concern, and more so if your home is really well sealed.  Note that furnaces and gas stoves require oxygen to burn their fuel.  If you operate a furnace or gas stove in a space that’s not well-ventilated, you’re going to get high levels of carbon dioxide first, and when the oxygen level drops enough to cause the furnace to have incomplete combustion, carbon monoxide is produced.  There is a simple fix for this: ventilate the space continuously, and install CO and CO2 monitor(s). 

There may be several other scenarios where oxygen concentration in your home suffers, and these are real, life-threatening situations.

  1. If you live in the mountains, you know that although the percentage of oxygen in the air is the same, the same volume that you breathe in contains less oxygen than at sea-level.  Our bodies compensate for the lower oxygen by increasing heart rate and respiration rate in order to cycle more air through our lungs.  Athletes sometimes train at high altitudes to gain “an edge” while competing at sea level.

  2. Fire requires at least 16% oxygen to continue to burn.  This is not a problem for most wildfires; as the air within a wildfire heats up dramatically, fresh air is sucked from surrounding areas.  If you live in an area prone to wildfires, you may experience high winds bringing fresh air–until the wind changes and smoke is the major problem.  In this case, smoke inhalation is deadly because of extreme heat of the smoke, oxygen depletion (hypoxia), and inhalation of noxious gasses carbon monoxide (CO), cyanide or hydrogen cyanide (CN or HCN), phosgene, ammonia, sulfur dioxide, hydrogen sulfide (H2S), formaldehyde, and acrylonitriles.  (Smoke Inhalation Injury: Etiopathogenesis, Diagnosis, and Management)  In this case, the presence of toxic gasses may be more life-threatening than low oxygen.

  3. As we mentioned above, living in a city during extreme heat or even inversion (many times this occurs during the winter), oxygen at ground level becomes depleted and this layer becomes more polluted and less oxygenated.  

Each of these situations can become life-threatening.  If you find yourself living in risk of any of them, the first step would be to monitor oxygen (and other pollutants for situations 2 and 3).  Unfortunately, most web-enabled monitors do not have oxygen sensors.  In fact, the only multi-sensor home monitor I could find that included oxygen is by Airovita, which is made in Europe and not sold in the US.  Don’t let this “hole” in the market stop you from being informed, however; handheld meters like this one ($100) that measure O2, CO, H2S, and explosive gasses are accessible so that you can be aware of how the atmosphere outside is affecting your home’s air.  In the case of high-altitude air, however, be aware that oxygen levels will register as “normal” (20-21%) but because of the low atmospheric pressure, you still may have trouble breathing!  

Unfortunately, making your air more breathable costs money.  The Washington Post notes that during wildfires, wealthier families flee smoky areas, staying in second homes or renting expensive hotels or vacation residences. Not all families can afford air purifiers, which start at about $200 and clean only one room. During frequent power outages that happen during fire season, only wealthier families that can afford expensive backup generators will still be able to run their purifiers.  Nonetheless, here are some solutions for making life safer and more comfortable: 

  • If you desire to add more oxygen to any room in the home (especially the bedroom, where your body repairs itself while you sleep), then companies like ACT (Altitude Control Technology) offer “altitude control”, meaning that with their controllers, ventilation and oxygen generators, you can change the atmosphere of that room to mimic living at a lower altitude.  Athletes can even use the system to change their workout room to a higher “altitude”.  Selecting a lower altitude creates an artificial “pressure” so that your lungs will receive more oxygen with less work.  Their equipment also includes particulate air filters to eliminate dust, viruses, bacteria, and fine particles as small as .3 microns to keep the air pure.  Truly, this system is the gold standard in creating the desired altitude, because of its oxygen machines, control system and custom designs for each room.  Alarms notify the user(s) of any unsafe conditions, and the air separation units are under low pressure.   

  • Since toxic gasses and particulates can be even more likely than low oxygen during a wildfire event, it’s best to start using air quality monitors to plan your days during these events.  When air outside is bad, closing up your home and using air filters can make it better.  As shown in the graphic below, indoor air sensors (left) are better than outdoor air sensors (right). (How much wildfire smoke is infiltrating our homes?)  Also, check out our article on how to prepare for wildfires and keep your air quality safe.

  • Ultra-filtration and oxygen generation technology can be adapted to any shelter, provided you have the budget!  “Bunkers” are not what they used to be.  Nowadays the mega-wealthy have underground swimming pools, gardens, and entertainment to escape whatever is happening above-ground.  Some developers are also acquiring decommissioned military bunkers and missile silos built by the United States or Soviet governments – sites that would cost hundreds of millions of dollars to build today. The fortified structures are designed to withstand a nuclear strike and come equipped with power systems, water purification systems, blast valves, and Nuclear-Biological-Chemical (NBC) air filtration. (Billionaire bunkers: How the 1% are preparing for the apocalypse

So, although oxygen depletion rarely happens at lower altitudes, if you have concern about it, make sure to measure it and then take action.  As John F. Kennedy said, “The time to repair the roof is when the sun is shining,” or in our case, the time to prepare our air is now!  Don’t wait for that extreme event to buy an air filter, learn how to control your home’s ventilation, or search for a getaway spot, because that’s what the majority of people will be doing.  Now’s the time to get ahead of the curve!

Photo by Jason Hogan on Unsplash

What do spiderwebs and your home’s air filter have in common? (no spider pictures)

What do spiderwebs and your home’s air filter have in common? (no spider pictures)

Spiderwebs–and the creatures that make them–are not welcome in most homes.  Not only are spiderwebs a “sign” of poor housekeeping (although they often appear overnight), spiders themselves are feared or despised (admittedly I’m in this group).  Even many nature-lovers would rather relocate the spiders and tear down their webs rather than abide with them, but scientists have recently discovered that their webs contain a wonder material that filters air akin to the best air filters. 

It’s obvious that spiders are probably not interested in reducing PM2.5 with their webs: their primary goal is getting dinner.  Face it, though: we all know that spiderwebs do a great job of collecting dust!  Scientists found that the electrostatic properties of the glue that coats spider webs causes them to reach out to grab all charged particles, from pollen and pollutants to flying insects.  A quirk of physics causes webs to move towards all airborne objects, regardless of whether they are positively or negatively charged.  Webs can catch particles as small as aerosols and pesticides, making them perfect environmental monitors if we choose to examine them.  (How electricity helps spider webs snatch prey and pollutants)

It’s the statement that “all charged particles” are attracted to the web that caused us to investigate further.  How does that work?  Typically electrostatic filters work by charging all incoming particles either positively or negatively and then attracting them with an oppositely-charged filter.  Spiderwebs are not exactly the same, because the web has no control of the charge of the particles (insects or dust) flying toward it, yet it actively “springs” out toward them if they are charged (click here to see it happen–no spiders included!)

The fact is that as things fly through the air, whether it’s dust, water droplets, insects or airplanes, they collect a static charge. This is why airplanes have little “antennae” or rods sticking out of the back of the wings: these static dischargers disperse the charge back into the air.  Insects can easily acquire electrostatic charge by walking over charged surfaces or by flying in an airstream of charged particles. (Spiderweb deformation induced by electrostatically charged insects)  Just as humans accumulate static by walking through dry air and carpets during winter, low humidity likely amplifies the static charge of insects, too.  The deflection of the spider’s web depends on the mass of the particle or insect and their charge; small charged dust particles generate less deflection than larger insects.  So, although insects have sensors on the tips of their antennae for detecting electric fields, and the glue spirals can distort Earth's electric field within a few millimeters of the web,  sometime the total charge of the insect or their speed gets them in trouble, allowing the web to “reach out and grab” them!

But how does the spiderweb attract positive and negatively-charged objects?    According to the scientists, this is due to the ion mobility within the miniscule water droplets that the web’s adhesive surface attracts. A combination of the spiders’ naturally compound-rich silk and the droplets (which serve as both glue carriers and electrostatic conductors) imbues the web with these amazing electrostatic properties.  ('Electric' webs are spiders' secret to catching prey)

Orb weaver spiders are the common class of garden spiders.  Their webs are formed roughly in a circular pattern, hence the “orb”.  Their webs are also hygroscopic, meaning that they absorb moisture from the atmosphere, using salts to retain a specific amount of moisture.  

Since there are more positive ions in the air than negative ones during calm weather, most insects gain a slight positive charge as they fly through the air.  The web is usually “neutral” meaning it doesn’t have a charge, but as an insect nears it, moisture on the web allows electrons to migrate to the surface of the web near the insect and cause the silk to stretch out toward it.  

Static induction is the principle that guides this phenomenon, which you've experienced if you've ever rubbed a balloon on your head and stuck it to a wall. Rubbing the balloon causes it to gain a static charge, and then it induces the opposite charge in the wall. Materials that are poor conductors, like rubber or silk, produce the best static induction.

Similarly, static induction occurs between the spider web and an insect. As an insect carrying a positive charge nears the threads of the web, that positive charge attracts electrons in the spider silk, creating a temporary negative charge. That negative charge can then be attracted to the positively charged insect, causing the spider threads to snap out and stick to the insect. (Note to Flies: Avoid Fuzzy Socks)

The drops of water on the web also allow glycoproteins in the web to move around it and coat any insects that become entangled in a sticky glue.  Glycoproteins are proteins that have carbohydrates attached to them, which allows the glue to form a large number of hydrogen bonds.  In these types of bonds, hydrogen forms a positive dipole in one molecule and fluorine, oxygen, or nitrogen form a negative dipole in another molecule. The positive dipole of hydrogen is attracted to the negative dipole on the electronegative atom, creating an attraction between the two molecules. (  Although the hydrogen bonds are relatively weak, they are collectively strong enough to keep insects and pollen from escaping the web. (Glue Stays Sticky When Wet)

Spiders depend on the invisibility of their webs to catch insects, so when the webs become “dirty”, many spiders clean and repair them on a daily basis (Spiders and Their Webs).  To replicate the web and this cleaning action, other scientists took on the mission in 2020 of creating artificial webs that attract and release particles in a self-cleaning action (Ionic Spiderwebs)

Instead of repairing them, some spiders ingest the old web and its contaminants, including the water droplets on the web.  Web material is hygroscopic, meaning that after it exits the spiders body, it attracts water from the atmosphere.  (Water harvesting during orb web recycling)  This actually helps the spider by giving it a source of water from the air.  The pollen on the web is a bonus too:  pollen makes up to a quarter of the diet of orb weavers. Unfortunately, a lot of urban spiders end up ingesting microplastics, chemicals and tire components (from road dust).  

Spiders also build their webs with a minimum of material, to reduce waste and avoid having to clean or eat extraneous web.   Because the web material is stretchy, sticky and because of static inductance, webs can be constructed with holes to let wind pass through, at the same time catching much more pollen and insects than any plain non-stretchy, sticky material.  “Avoiding” capture is much harder for any insect or bit of pollen trying to fly “through” the web when its holes can close automatically by static attraction!   Simply put, spider webs are amazing particle capture machines, also known as filters.  It’s no wonder then that scientists are busy replicating them for different purposes.

Spider‐web‐inspired network generator (SWING) air filters, based on a unique electrospraying–netting technique, integrate properties of small pore size (200–300 nm) and innovative self‐charging capacity (3.7 kV surface potential), enabling the synergistic effect of physical sieving and electrostatic adhesion for PM removal.  High efficiency (>99.995%), low pressure drop (<88.5 Pa), high transparency (>82%), robust bioprotective activity, energy‐saving, and long‐term stability for MPPS PM0.3/pathogen removal were achieved.  The filters are made of electrospun nanofibers (PVDF material) and carbon nanotubes, which are uniquely formed by using a droplet spray–deformation–assembly process during electrospinning (Spider‐Web‐Inspired PM0.3 Filters Based on Self‐Sustained Electrostatic Nanostructured Networks)

The silk proteins in spider webs themselves were determined in the early 2000’s (Spider Silk Proteins – Mechanical Property and Gene Sequence).  Spider silk is desirable not only for strength (it is superior to nylon, kevlar, silkworm silk and steel in elongation at break, tensile strength and breaking energy), but it’s also bio-compatible to humans and so can be used in medical applications.  Artificial spider silk has not been easy to develop.  Although the primary proteins were discovered earlier, It took a lot of gene-sequencing work to discover a formula for getting the optimal amount of nanocrystals in the silk.  Once the protein sequence was determined, scientists needed to figure out who or what should be used to make the silk?  Spiders themselves are too aggressive and territorial to be farmed. (Artificial Superstrong Silkworm Silk Is 70% Stronger Than Spider Silk)  For this reason, bacteria, silkworms and goats have been bio-engineered with spider DNA to produce the silk. (Artificial Spider Silk Is Stronger Than the Real Thing, Spider Silk, BioSteel Goat)

Filter production methods: Traditional Needle Electrospinning (ES) requires extensive preparation, time, and post-treatment to produce filter material, as shown in this video.  In this article, Centrifugal Electrospinning (CES) was found to be the most effective method in mimicking the fiber and composition of spider webs, albeit in a random non-woven way.  The suitable spinning conditions for the recombinant spider silk protein eADF4(C16), including protein concentration, process flowrate, electric field strength,and rotational speed were analyzed.  Experimentation with these variables enabled researchers to develop a roll-to-roll production process that is up to 1000 times faster than traditional electrospinning processes that also required no post-treatment.  

So–knowing that spiderwebs are such efficient filters and their silk is now the object of much scientific research and investment, has this information changed your opinion of spiderwebs in your home?  It’s ok, I know that fear of spiders is hard to dispel.  So with you, I say, bring on the artificial spider silk, please! 

Are There Water Filters Growing in Your Backyard?

Are There Water Filters Growing in Your Backyard?

According to a March 2023 United Nations World Water Development Report, around 2 billion people do not have access to clean and safe drinking water.  (Billions of people lack access to clean drinking water, U.N. report finds)  Many organizations develop new water filters every year, but the major problems with these filters are the cost and availability: even relatively low-cost filters are prohibitively expensive for many.  Also, people would rather pay small daily increments for fresh water rather than a single large payment for a filter.  This is one reason that many people in India pay daily to have access to fresh bottled water, rather than purchase a filter that costs more. 

Researchers at MIT found that local trees have natural filters that can actually purify water to drinking water standards. (MIT engineers make filters from tree branches to purify drinking water)  Xylem is the vascular tissue that conveys water and dissolved minerals from the roots to the rest of the plant and also provides physical support. Xylem tissue consists of a variety of specialized, water-conducting cells known as tracheary elements. (  The interiors of non-flowering trees like pine and ginkgo have sapwood that contains xylem which even filters out bacteria.  The sapwood of such trees also have shorter conduits in the xylem than flowering trees, so that water must pass through a number of “pores” in the xylem, which are the main filter elements that remove microbes.  In trees, the pores are not used to filter water, but rather separate gas bubbles that would block the xylem.  Here is a diagram of how water is filtered through xylem; the pores being the disc-shaped aperatures:

Courtesy: N.R. Fuller, Sayo Studio

Although the images above are microscopic, the entire filter is a 1-cm long piece cut from the cross-section of a branch:  

Source: Xylem Water Filter manufacturing process video

Next, the wood filter is inserted into a tube and secured with a hose clamp.  Voila, you have the main part of your wood water filter!

Source: Make your own Xylem Water Filter! video

Two additional preparation steps of soaking the wood filters in ethanol and drying them out completely in an oven caused them to be less prone to clogging, as well as extending their shelf life.  

The researchers took the concept to a suburb in the Indian city of Delhi, where 30 million people live.  Many people there are susceptible to intestinal illnesses and death due to poor quality drinking water.  The MIT team went into neighborhoods with water access issues and demonstrated that the filters were simple and cheap to replace.  Many people who saw them demonstrated confirmed that they could either make or purchase the wood filters sustainably, for easier access to clean water.  

Want to make a xylem filter yourself?  This free website gives all the information needed to select a tree and construct the filter, which is a great science experiment for kids.  

The filters are still under development, because it’s not known whether they can remove chemicals, metals or other contaminants.  However, unlike many novel water filters coming from universities or private firms, this one is quite inexpensive, simple and has easily-sourced parts.  It seems that even survivalists should be glad to know this information–and you might want to keep it handy for your next camping trip!

Photo by Airam Dato-on on Unsplash

To-Do List: Change the Cabin Air Filter in your car and ADD CARBON!

To-Do List: Change the Cabin Air Filter in your car and ADD CARBON!

I know, car maintenance is not everyone’s “thing” and air filters sound super-boring.  However, if you’ve owned your car for a while and never changed the filter, or bought a used car and have no clue when this filter was last changed, you could be horrified at what you would find (and hence are breathing in every time you drive it)!  It’s time to think of this task as a “health upgrade” for you, the driver or passenger!

Cabin air filters in cars (tip: these are different from the engine air filter) are probably even more neglected than household air conditioning or furnace filters, for several reasons:  our car ventilation systems are exposed to even more dust, toxins and critter debris than our homes, and many people are averse or afraid of car maintenance.   However, it’s so easy to order the right filter online with your car’s model and year, and now virtually every maintenance procedure on every model car can now be found on YouTube.  There’s no excuse for rolling up your sleeves and getting to it (or bribing your teenager or neighbor to do it with some food)!   Simple tools like screwdrivers, sockets and a vacuum cleaner are usually the only things needed. 

Before you order the filter, however, check to see if they are available with activated carbon.  If so, definitely get that one.  Not only does carbon help with smells in your vent system and car interior, it can remove NO2 from ventilation air.  Nitrogen Dioxide (NO2) is a by-product of fuel combustion and it irritates our respiratory system, causing flare-ups of asthma, which can trigger a visit to the emergency room if the coughing and difficulty of breathing is not controlled.  Over time, NO2 can actually cause asthma or respiratory infections.  A study in the UK at the University of Birmingham showed how much the activated carbon lowered NO2 levels compared to basic pollen filters.  In heavy traffic, many people close the windows and put the ventilation system on “recirculation mode”, which helps reduce NO2 levels by about 1.6 times compared to open windows.  However, you shouldn’t keep the windows closed and recirc on for extended periods of time because CO2 levels will start to rise; maintaining appropriate ventilation is also important to prevent drowsiness.  Here’s the alternative:  using external ventilation with activated carbon filters fitted.  Even with fresh air coming through the ventilation system, NO2 levels were 6.6 times lower than levels with windows open.  Also, in-vehicle NO2 levels were on average 14.3 times lower with closed windows and recirculated air.  It just makes sense to go with activated carbon if it’s available in a filter for your car. 

With minimal research and $, you can feel a lot better about the air you breathe on every drive.  Then, you can place a reminder on your calendar to do it again next year, and keep up the good habits!

Photo by Ivan Bogdanov on Unsplash

Phytoremediation Cleans Up Soil Naturally

Phytoremediation Cleans Up Soil Naturally

It’s happened to the most careful and graceful of us: a cup of coffee or plate of spaghetti sauce lands on the carpet, upside-down, of course. Out come the carpet cleaners, vacuum cleaner, or if you’re really prepared, the carpet-cleaning machine, and we do our best to treat the area and cordon it off for “drying”.  If the offending stain doesn’t appear again, case closed.

But what if you or someone else spills a toxic chemical on a large area of your lawn?  How do you remove that? There are no “lawn cleaners”...or maybe there are. 

The Environmental Protection Agency (EPA) is the U.S. agency concerned with not only monitoring, but cleaning up those big spills or more unfortunately “dumps” in the U.S.  It mandates how the sites are cleaned up and should hold individuals or corporations liable for the damage.  Unfortunately, as long as there is industry, there will be accidental, and often intentional, spill on land and water.  However, sometimes, the “cleanup” may not look like cleanup at all, if phytoremediation is used.  A toxic waste cleanup site may look like any other green field.

Phytoremediation refers to the different ways plants can be used to “clean up” contaminated soil.  Around  400  species  of  plants are called “hyperaccumulators” because they absorb unusually large amounts of metals in comparison to other plants.   These  plants  have  been found to accumulate metals at a rate 50 - 100 times higher than normal plants.  (Phytoremediation of soil metals)  They do this in a number of ways; the following terms are taken from the EPA’s Phytoremediation Resource Guide:

  • Phytoextraction: some plants take up metal contaminants in the soil by plant roots and move them into the aboveground portions (stems, leaves, fruit). 

  • Rhizofiltration: some plants adsorb contaminants from ground water onto their roots, or in the case of aquatic species, the plants live in contaminated water (like wastewater). Duckweed is a species that has been shown to remove many types of heavy metals from water. (Duckweed: A Model for Phytoremediation Technology)

  • Phytostabilization: some plants are used to immobilize contaminants in the soil and ground water through absorption and accumulation by roots, adsorption onto roots, or precipitation within the root zone. This process reduces the mobility of the contaminant and prevents migration to the ground water or air, and it reduces bioavailability for entry into the food chain.

  • Phytodegradation: some plants take up contaminants and break them down through metabolic processes within the plant, or through the effect of compounds (such as enzymes) produced by the plants. Pollutants are degraded, incorporated into the plant tissues, and used as nutrients.

  • Rhizodegradation:  the breakdown of contaminants in the soil through microbial activity that is enhanced by the presence of the rhizosphere and is a much slower process than phytodegradation. Microorganisms (yeast, fungi, or bacteria) consume and digest organic substances for nutrition and energy.  This is becoming a very popular topic and technology as scientists learn how to modify and genetically engineer microbes for particular purposes.   

  • Phytovolatilization:  some plants are able to take up and transpire (breathe out) contaminants, releasing the contaminant or a modified form of the contaminant to the atmosphere.  It is known that trees with deep roots transpire radon from the ground and groundwater.  

So, once the area is planted with hyperaccumulating plants, what happens next?  Unless the contaminant is phytodegraded, meaning, the plant breaks it down, the plants will still contain the contaminants, so they must be harvested and disposed of properly.  If testing reveals that they indeed have higher-than-acceptable levels of the contaminants (actually, this is a good outcome), they are either composted or dried and incinerated, and the waste remaining is securely buried.  Then the process is repeated until the soil is cleaned to an acceptable level.  The difference between phytoremediation and traditional soil removal is huge:  typically the amount of material to be incinerated from phytoremediation is only 10% of that required by traditional soil removal.   Here is a video of an EPA phytoremediation project in Crozet, VA where arsenic is removed from the site of an old apple orchard by planting and harvesting ferns that were bioengineered for the purpose of extracting arsenic.

What does this mean for the average homeowner?  Unfortunately, many private lands are poisoned with any number of contaminants: lead paint from old buildings, pesticides from farms and aerial contaminants that settle from spraying for insects or crops are all sources of contaminants.   You might not even be aware of old fuel tanks or lines that were buried decades ago, before you purchased the land, and have begun to leak, or maybe a new industry is releasing chemicals upstream of your land.  With any knowledge or suspicion of contamination, consider if you or your family will be exposed to the soil, and decide whether to get the soil tested.  If children or animals are regularly in contact with the soil, or you want to grow edible plants and vegetables on the land, testing is a good idea, so you know what chemicals you’re dealing with and which plants may be able to help you!  Here is a great article on how to gather soil samples and available testing centers. 

If you do find contamination on your land, here are some actual plants that could help clean up the soil: 

  • Grasses: Indian Grass has the ability to detoxify common agrochemical residues such as pesticides and herbicides. Indian Grass is one of nine members of grasses that assist in phytoremediation plants. When planted on farmland, the reduction of pesticides and herbicides is significant. This list also includes Buffalo grass and Western wheatgrass, both capable of absorbing hydrocarbons from the land. (Phytoremediation Plants Used to Clean Contaminated Soil)

  • Sunflower plants were demonstrated to have removed 95 percent of uranium from a contaminated area in a 24-hour period. This highly successful crop is a powerful tool for the environment because of its ability to remove radioactive metals from superficial groundwater, so they were used in cleanup after the Chernobyl nuclear disaster, which left nearby soil and water heavy with the radioactive elements cesium and strontium. The process works because the isotopes “mimic” nutrients that the sunflower would naturally absorb – cesium mimics potassium, which plants need for photosynthesis, and strontium passes for calcium, which provides structural support. Unfortunately, sunflowers did not work so well for Fukushima, Japan, because the isotopes released were very different from Chernobyl. (Why Scientists Plant Sunflowers After Nuclear Disasters).  Sunflowers are also good at absorbing metals such as lead, arsenic, zinc, chromium, copper and manganese. Indian mustard removes lead, selenium, zinc, mercury and copper.  Hydrangeas draw out aluminum from the soil.  (Superplants clean up toxins from contaminated soil)

  • Trees can do their part:  Willows and poplars have been shown to be strong phytoremediators, not to mention being beautiful.  Carbon tetrachloride, a well-known carcinogen, is easily absorbed by poplar tree roots. They can also degrade petroleum hydrocarbons like benzene or paint thinners that have accidentally spilled onto the soil. (Phytoremediation Plants Used to Clean Contaminated Soil)

  • Vegetables:  Of course, if you know that there’s soil contamination and you grow vegetables to remove it, you must take care not to let anyone or any animals eat the vegetables or plants.  Certain vegetables only take contaminants into their root systems, but others draw them up into the leafy greens of the plants.  Cruciferous vegetables like broccoli, kale, collards, mustards and also corn are considered hyperaccumulators.  (Superplants clean up toxins from contaminated soil)

  • Mushrooms: Like phytoremediation, mycoremediation is the use of fungus or microbes to clean the soil.  It’s hard to believe that edible mushrooms are in the same class as toxic mold, but they are both fungus, and can be used to absorb and/or break down pollutants.  As mycelium spreads, it secretes enzymes which can break down pollution.  For example, oyster mushrooms have been used to remove E. Coli from Chicago River water, harmful Polycyclic aromatic hydrocarbons (PAHs) and TNT from water sources contaminated by wildfire ash, and diesel-contaminated fields from 10,000 parts per million (ppm) of PAHs to less than 200 ppm in eight weeks.  Turkey Tail, Shiitake and White-Rot Fungus are three other useful mycoremediators. (Mycoremediation: 8 Ways Mushrooms Can Mitigate Pollution)

The downside of hyperaccumulating plants is when they are grown and consumed without testing/regulation of the contaminants in them.  Unfortunately, brown and white rice (they are the same grain; brown rice is simply the whole grain while white rice has been milled and polished) are hyperaccumulators of cadmium and arsenic.  Arsenic is a more common pollutant; in the US, it gets into rice through pesticides used in old cotton fields that are flooded to farm rice, and through contaminated groundwater that floods fields in Bangladesh, for example.  The rice plant often takes up arsenic in place of silicon; rice plants require large amounts of silicon for optimal growth, and the chemical form of arsenite (AsIII) is very similar to silicon.  (Arsenic Transport in Rice and Biological Solutions to Reduce Arsenic Risk from Rice)  This is a very serious problem in eastern cultures where rice is a main staple of the diet for millions of people, and even those who can’t eat gluten, a protein in wheat that causes severe allergies in some people.

Unless you are reclaiming a swamp, new pristine land is not being created in great quantities, so we’re left with land that has centuries or millennia of human footprints, including toxic chemicals and metals.  Human use of the land in general leaves it in worse condition, but with the right plants, it’s possible to reverse a lot of the contamination.  If you want to make your own land–whether it’s your suburban backyard or acres in the country–cleaner and more habitable, get the soil tested and research which hyperaccumulating plants will make it better.  Once you get past the latin plant classifications, you may find the right plants also bring aesthetic beauty you wouldn’t have imagined. 

Photo by Markus Spiske on Unsplash

Volcanic Ash, Repurposed

Volcanic Ash, Repurposed

Inferring from news headlines, you might think that volcano eruptions are rare–maybe a couple a year.  This is definitely not the case!  As of April 14, 2023, there were 49 volcanoes in eruption, 75% of them along the “Ring of Fire” where the Pacific Ocean meets land masses on the west and east.   To see the names and places of these active volcanoes, check out this page in the Smithsonian’s Global Volcanism Program.

Volcanoes emit several things when they erupt.  Gasses are composed of water vapor, carbon dioxide (CO2), sulphur dioxide (SO2), and hydrogen sulphide (H2S).   In actuality, lava can also contain 6% or more of its mass as gasses.  The gasses come out of solution from the lava when it erupts from the ground, in the form of bubbles or explosions.  (Volcanoes) Lava can flow in many forms above ground, below ground, and underwater.  The chemical composition of the lava causes it to have different viscosities and take different shapes as it cools and solidifies.  This page has a detailed description and fascinating photos of the many different types of lava.  

When gas and solids are emitted at the same time from a volcano–watch out!  Pyroclastic flows are the most dangerous type of eruption, where the hot pressurized gas can carry fragments of rock and ash for long distances.  Boulders can be thrown for miles if the eruption is particularly energetic, but the main danger for nearby residents is lava, fragments of rock called pumice, hot ash and gasses.  It was once thought that the residents of Pompeii perished due to suffocation of ash, but new evidence points to extreme heat.  (The Hazards of Pyroclastic Flows)

Clouds of ash can travel thousands of miles in the atmosphere.  It can disrupt airplane traffic and cause air pollution in distant cities, but when “the dust settles”, volcanic ash can be a good thing, as it’s used for many purposes.

Solid particles emitted from volcanoes are collectively called tephra.  Products made with tephra can be from ash (fragments of rocks, minerals, and volcanic glass ranging in size from sand to clay-like (from 2 mm to less than 0.004 mm in diameter) which is hard and abrasive), or milled/crushed from larger rocks and pumice.  Here are a few examples:

  • Bricks made with 10-20% ash of Mt. Etna, a very active volcano in Italy, were less porous, more compact and less susceptible to decay, with a small loss of strength that was still in acceptable parameters. (Producing Bricks with Volcanic Ash from Mount Etna)
  • Concrete made with 30-50% ash vs. 100% Portland cement is less energy-intensive to make and is stronger. (Cities of the future may be built with locally available volcanic ash)
  • Volcanic ash can make soil incredibly fertile due to the different minerals it contains. 
  • Volcanic rock can be used to purify water.  This use is discussed in the rest of this article.

Zeolites are natural volcanic minerals with unique characteristics. They are aluminosilicates, meaning that they are composed of varying quantities of aluminum, oxygen and silicon.  Zeolites were formed when volcanic ash was deposited in ancient alkaline lakes. The interaction of the volcanic ash with the salts in the lake water altered the ash into various zeolite materials, creating “pores”.  The pores have typical diameters of 0.5 to 0.7 nm, which are slightly larger than the diameter of a water molecule. Positive ions are present in the channels, which can be exchanged for other ions.

This substitution of ions enables zeolites to selectively adsorb certain harmful or unwanted elements from soil, water and air. A good example is the removal of calcium from hard water, also called "softening".  In this case, zeolites exchange sodium ions for calcium ions, which result in soft water. Zeolites also have strong attraction for certain harmful heavy metals such as lead, chromium, nickel and zinc. (Zeolites)

The oldest evidence of use of volcanic rock in water purification exists at Tikal, a Mayan city in northern Guatemala.  The Maya collected zeolite and quartz from a crystalline tuff (a light, porous rock formed by consolidation of volcanic ash.) about 30 km northeast of the city between ~ 200 BC and 1000 A.D. They used these natural volcanic mineral resources to purify large volumes of drinking water in a tropical forest environment, which was complicated by catastrophic cyclones, volcanic events, droughts, and subsurface drainage; this is the oldest known zeolite water purification system. (Zeolite water purification at Tikal, an ancient Maya city in Guatemala)

Zeolites can also be synthesized  from volcanic ash.  In an effort to reduce landfill disposal of the ash surrounding Mt. Etna in Italy, two samples of ash were processed to form a synthetic zeolite that could adsorb cesium (a radioactive element) from polluted water. (Synthesis of zeolite from volcanic ash: Characterization and application for cesium removal)

For those whose interests lie more in beauty products, volcanic material has moved beyond pumice stones used for foot exfoliation and now the ash is having a moment in skin creams, masks and primers.  The minerals in volcanic ash (including sulfur) are antibacterial, anti-inflammatory (when used temporarily and correctly) and some products can be used to exfoliate and dry especially oily skin.  Three dermatologists weigh in on volcanic ash’s skin-clearing properties in this article.

How can you use volcanic ash or zeolite around your home? (Zeolites-applications)

  • For adsorbing odors: in shoes, carpets and kitty litter
  • For absorbing fat runoff in barbeque pits
  • For adsorbing moisture in closets and cabinets
  • As a filter medium for your fishtank (adsorbs ammonia)
  • As a filter medium for an air purifier (removes ammonia, formaldehyde, and other VOCs)
  • As a filter medium for water purifiers and softeners
  • As a garden soil additive for drainage, minerals and for landscaping textural interest

The minerals and rock formations of volcanoes vary endlessly in composition and uses.  Volcanic ash and zeolite are another of the earth’s natural filters and cleaners.   As our air and water become more polluted, we expect these resources to be used in many more ways–another example of taking “waste” and repurposing it for a cleaner environment.

Photo by Yosh Ginsu on Unsplash

What is Salutogenic Design? How can we use it in our homes?

What is Salutogenic Design?  How can we use it in our homes?

Salutogenic design comes from the two Latin words ‘salus’ meaning health and ‘genesis’ meaning origin.  It is the study of the origins of human health.  Aaron Antonovsky was an immigrant to the US in the 1920’s, eventually being drafted into the US Army in World War II and serving in the Pacific.  Much later after obtaining his doctorate in sociology, Aaron studied survivors of concentration camps and wondered, why aren’t more of them in very poor health?  It was his questioning of the means and causes of good health, rather than what causes disease, that set him apart. (The Handbook of Salutogenesis, Chapter 3, Aaron Antonovsky, the Scholar and the Man Behind Salutogenesis

Normally salutogenesis is focused on healthcare settings and providers.  However, we can take the same concepts and apply them to our workspaces and homes. In today’s news, we’re constantly being made aware of environmental and human threats like viruses and toxic spills that threaten our health.  The possible effects,  such as cancer, high blood pressure, and sickness, are always presented to admonish us, avoid this or suffer consequences!  It’s definitely hard to tune out these sources.  However, if we’re able to focus on what makes us feel good, the results could be much greater.  Whether you’re designing a home from the ground up or have some time and budget to make some changes, here are some concepts from salutogenesis to keep your perspective in the right place: your health.

Louisa Grey is a designer living in north London who has embraced salutogenic design.  She prioritizes space, light and air in her projects by identifying the direction of natural light and the optimum layout to encourage airflow.  She admires the design of southern Italy’s trulli (ancient homes made out of limestone with conical roofs) and often incorporates a similar building material–clay–in her modern works, because it is naturally abundant, has acoustic-controlling qualities, is dehumidifying, regulates temperature and can improve air quality.  Clay plaster on walls has a soothing texture and appearance that gives a rustic, hand-crafted look to rooms, which also saves on energy in manufacturing and reduces waste. (Interiors expert Louisa Grey on how to embrace salutogenic design)  

Well-placed windows should allow the right amount of sunlight into your home, such that it doesn’t cause a large cooling load but rather allow a range of filtered or dappled light.  There are a number of companies that also offer faux skylights (thus avoiding any leaks or roof problems!) when natural light is at a premium.  

Open-concept floor plans do have the advantage of seeming more spacious than the same size traditional floor plan, but there is also comfort and peace in having walls and doors define some spaces, like an office or home library.   

Porches, courtyards and the ability to open large windows or doors to the outdoors (in areas with good air quality) are very beneficial because they allow fresh air to fill your home and to warm or cool it.  Plus, they are an ideal place to keep plants that need a little shade or protection and surround your seating areas in green.  Even views of green–from inside the house–lower stress, lower blood pressure, improve cognitive functions (like your ability to learn or focus), increase productivity, reduce anxiety, improve mood … the list is extensive! (How Your Home’s Design Can Improve Your Health)

If you are not building from the ground up, however, there are still ways to apply this type of design in your home.  According to the previous source, one of the most popular methods of salutogenic design is to incorporate biophilic design, which is based on human’s innate connection to nature. To do this, you can incorporate plants into your home, a calming mural, or the actual “architecture” of nature such as a natural stone fireplace, spiral staircase, or live-edge shelving that protrudes at different widths and heights on a wall.  Honeycomb shelving or tiled floors also mimic natural shapes.

Texture and comfort inside the home are very important.  (Although rugs and upholstery can hold dust and dust-mites, the way they “warm up” a room to make it inviting and comforting is important enough to use them when you can.  Also according to Louisa Grey, scents are can also be a healing part of your home: try to use natural oils and purifying mists and flowers that are grown locally. (How to design a healing home – and the power of salutogenic design)

Salutogenic design can even encourage healthy behavior when features like stairs or a swimming pool are included, or workout areas are not tucked away into a back corner or basement (you pass by them on a regular basis).  A beautiful library space, whether it’s an entire room or several bookshelves and a comfortable chair with good light also encourages learning. (Salutogenic Approach to Design is at the Core of Wellbeing)

Salutogenic design follows the principle that “an ounce of prevention is worth a pound of cure”.  Many homeowners make this choice everyday: should we go for small pieces of quality workmanship in our decor, appliances and clothing, or larger but lower-quality items?  It’s true that good design, building and decor may cost more than “builder’s grade” plans and materials, but what you should reap is a lifetime (or at least as long as you can live there) of better air quality, ergonomic ease, increased productivity and creativity, lower stress and overall wellbeing.  Who can put a price on that?

Photo by Andrea Davis on Unsplash

The Differences between a Cleanroom and Your Home

The Differences between a Cleanroom and Your Home

Don’t you wish your home could be called a “cleanroom”?  Well–maybe in name, but it takes a lot of expensive equipment and protocol to make it happen!   Cleanrooms were first invented by scientist Willis Whitfield while he worked at Sandia National Laboratories in New Mexico in the early 1960’s.  He developed the first forced-air filtration system to control the number of airborne particles within an enclosed space. (The History and Innovation of the Cleanroom

A cleanroom is a controlled environment that filters pollutants like dust, airborne microbes, and aerosol particles to provide the cleanest area possible.  Cleanrooms are used for many different purposes; some examples are in electronics manufacturing, medical equipment and pharmaceutical manufacturing, research labs, and hospitals.   There are nine “classes” of cleanrooms according to ISO 14644-1, which regulate the maximum number and size of particles, air change rates or airflow velocity, and percentage of ceiling coverage. (Cleanroom Classifications)  For example, Class 1 is the “cleanest” and only 0.35 particles per m3 of ≥0.5 micron particles are allowed, the air change rate must be between 360 and 600 times per hour, and airflow velocity ranges between 60-100 feet per minute, among other regulations.  In contrast, typical office building air contains from about 15,000 to 30,000 particles (0.5 microns or larger) per cubic meter of air. (A Basic Introduction to Clean Rooms)  We’re talking mega-fans, filters and restrictions to turn an office into a cleanroom!

Why must cleanrooms be so…extreme?  Well, dust is a big problem for certain products.  In the case of pharmaceutical products like syringes and medications, airborne particles provide a ride for microorganisms on which to produce, leading to contamination of product. (Keeping Clean Rooms ‘Clean’)  Other surfaces like electronics are very sensitive to contamination by dust, and dust or microbes can wreck many scientific experiments.

The biggest contamination risk to a cleanroom and its products is people.  Did you know that when you are just sitting or standing completely still , the average person is releasing up to 100,000 particles per minute which are 0.3microns or larger?  Increased activity increases these numbers, so people in the cleanroom are encouraged to move slowly (no fast walking or running, and definitely no horseplay is allowed!)

In order to keep the cleanroom, ahem, clean, people entering must follow certain common rules, of which here are some examples:

  • No personal items such as watches, keys, or phones may be brought in because of the risk of bringing in other contaminants with them.
  • No eating, smoking or chewing gum in the cleanroom.
  • No cosmetics such as perfumes, lipstick, nail polish or makeup are allowed because many cosmetics contain sodium, magnesium, silicon, calcium, potassium or iron, which can create damaging particles..
  • Don’t enter if you’re unwell–germs are definitely not welcome in the cleanroom, and frequent coughing or sneezing expels many more particles into the air than normal. 
  • Fabric or paper towels are not permitted! (They shed too many particles.)
  • Hair and facial hair must be covered up, because human hair is many times larger than permitted particles in the cleanroom.

Of course, dressing to go into a cleanroom is a production.  One suggested procedure lists 42 different steps to put on the white “bunny suits” that are made of a special lint-free material!  You must remove offending items from your pockets, wash off makeup or perfume, drink some water to rinse particles from your throat, clean your shoes and put on booties first, then move on to putting on the suit, helmet, faceshield, gloves, belt, and cleaning any equipment you take with you. 

To remove all the particles generated by people and manufacturing processes, detailed engineering and specification of the ventilation system is required.  Designers may start with the classification of the cleanroom and the required “air changes” for the size of room.  Then, they must factor in the number of people, type of work, lighting, and outside ventilation required.  For example, if hazardous fumes are developed, then the cleanroom needs to be able to filter and provide 100% outside air!  Humidity and temperature inside must also be specified and controlled.  The filter size and type must be adequate to handle the particle load for reasonable filter life, as well.  These are just some of the details that go into cleanroom ventilation design. (HVAC Cleanroom Design Calculation Explained)  This is way more intensive than your basic home HVAC design!

The “envelope” of the cleanroom, or its air circulation boundaries, are very important.  By implementing a positive or negative pressure in the cleanroom, the flow of air and contaminants are controlled.  Positive pressure cleanrooms are better at keeping outside contaminants out, such as for semiconductor manufacturing, because air rushes out of the room whenever a door is opened.  Negative pressure cleanrooms are designed so that fumes and particles generated inside it don’t escape (like for a hazardous microbe research facility).  For this reason, special air-sealed doors are often used so that an “air lock” is created and entry/exit is tightly controlled.  Sliding and swinging doors must also open slowly in order to avoid disturbing pressure gradients inside the room. (Understanding Air Pressure In Cleanrooms)

The other major concern in cleanrooms besides dust is static charge.  Not only does dust itself carry static, people generate static charge when they are walking or working, as their clothes rub together and across certain surfaces.  Did you realize that walking over a carpet can generate 35,000 volts, and the human body feels a shock when the voltage is higher than about 3,500 volts?  (Static Electricity)  Sensitive electronics can be damaged at voltages far below 3,500 volts.   For this reason, most cleanrooms are equipped with ionization equipment (similar to HypoAir’s Bipolar Ionization, actually) that disperse ions into the air so that positively or negatively charged surfaces are changed into neutral surfaces very quickly.  Ionization equipment may be installed in the fans, or attached to rods and beams that are suspended in the room.  Airflow and ionization are designed together in order to deliver the ions to work surfaces in the least amount of time, thus neutralizing charges quickly before they build up and cause damage. 

Even with all this technology of filtration and ionization, extreme manual cleaning is still required in cleanrooms.  This checklist of cleaning suggests mopping the floors, vacuuming the walls, wiping down all surfaces and cleaning all windows before every shift/between shifts.  Wow!  That’s truly the kind of clean you can “eat off of”.   

So…how do the principles of cleanrooms relate to our own homes?  Of course it would be nice to live in a space with so little dust and germs, but it’s just not practical, nor comfortable–homes just would not be homes without eating, cooking, good smells, playing games, pets, comfy soft materials and many more activities and things!   However, there are definitely some things to learn from cleanrooms. 

  • Watch what you bring into the house!  In our article “Check them at the door! ”, we explain how to bring how to bring less contaminants into your house by taking your shoes off (and having a place to store them), getting a good doormat, and manage pets that bring in contaminants.  It also helps to get a floor cleaning tool that you will use often.  I absolutely love using my CrossWave floor and area rug cleaner by Bissell ($257); it’s cut my floor cleaning time in half by vacuuming and mopping at the same time.  If you check local discount stores, there are many reconditioned models that sell for less than half this price (I got mine at Ollie’s).  In addition, of course the manufacturer wants you to use their patented floor cleaner, and states that using any other cleaner will violate the warranty.  Unfortunately, Bissell products mostly rate an “D” grade from the Environmental Working Group for toxicity to humans and the environment, but if you do decide to substitute a non-toxic cleaner, we have just the one for you: TotalClean.  With no fragrance and no toxicity, you can clean your floors as often as you want without adding more VOCs and chemicals to your home. 
  • Use the best filtration you can afford to cut down on dust and microbes in your air.  Obviously you don’t want the constant whir of ventilation or to change 14 filters a week like cleanrooms, but using a MERV 12-13 filter in your HVAC and changing it regularly will help minimize breathing in particulates.  If you live in an urban or dusty area, add standalone HEPA filters to your home. 
  • Use Bipolar Ionization to control dust, microbes and static too.  Cleanrooms depend on ionization to control static charges, but they also benefit from the other effects of this technology:  ions help the filters to grab more dust and ions disable microbes like viruses and bacteria.  Our Germ Defender, Upgraded Air Angel Mobile and Whole Home Polar Ionizer each send out millions of ions into the air to do the same thing in your home. 
  • Try to keep the cleaning on schedule.  We know, life gets in the way of routine a lot of times.  However, when the cleanroom doesn’t get cleaned on time, things start to go awry, and when your home suffers from cleaning neglect, your own health could suffer for it!  Enlist help, reward yourself, do whatever it takes to keep the dust and germs at bay, because a clean home is really a dose of good medicine for your own body! 

How do Electrostatic Filters work?

How do Electrostatic Filters work?

It seems like manufacturers are coming out with new filters all the time.  Filters for homes with pets, filters for allergies, filters against viruses…and on and on.   I recently ordered and replaced my HVAC filter with a brand name that was a pleated filter advertised as an “Electrostatic Air Cleaning Filter”.  I had to find out what that meant!

First of all, I thought that electrostatic filters had to be hooked up to electricity.   Actually, only some of them do.  Electrostatic filters encompass a broad range of devices, and the ones that do require electricity are usually called electrostatic air precipitators.  The principle behind these units uses elements to impart a charge to incoming air particles, and then attract them (make them stick to) an oppositely-charged plate.  These systems could be portable, or installed in your HVAC system, or be a part of a huge commercial operation (like a smokestack).   Typically these systems are powered by a high-voltage, low wattage system.  The “filter” is the entire unit, and instead of replacing any parts, the charged plates are simply washed clean. 

However, I bought a regular pleated-type replaceable filter with a large wire grid over it, presumably just to keep the filter in shape as you try to manipulate it to fit in your HVAC.  I don’t have any electricity supplied to the filter box of my HVAC.  How could this filter be electrostatic?

The answer lies in triboelectricity, also called static electricity.  As air whizzes through the synthetic fibers of the filter, the fibers become charged with static electricity.  Then they start to attract the particles of dust in the air.  Making the filter “pleated” increases the surface area of the filter over a flat filter, so that it can attract more particles.  Eventually, however, the fibers become coated with dust, and it no longer acts as an electrostatic filter, but continues to trap dust by the other methods of normal filters (we discuss those four methods here).  And, hopefully before the filter gets so full that dust starts to bypass it, it gets disposed and replaced or cleaned.  

Reusable, washable electrostatic filters are also available.  Washable filters typically have aluminum or galvanized frames and polyester filters so they can withstand repeated cleaning.  However, these typically have a lower MERV rating (only up to MERV 9), so they are not capturing the smaller particles of bacteria, viruses and mold spores that disposable filters can handle.  For more explanation on MERV ratings, check out this article

You can also make your “electrostatic” filter perform even better by using an ionizer in the same room as your filter.  Because ions are charged molecules in the air, as they collide with dust, they impart the same charge to the dust.  This “pre-charges” the dust and causes a greater attraction to the fibers of the filter.  In this 2015 study, researchers showed that unipolar ionization (as opposed to bipolar) enhanced the filtration by 40%, with a lower pressure drop than filters that remove finer particles.  

Whether your HVAC filter is electrostatic or not, the most important maintenance task is to clean or replace it regularly!  This is the only way you can ensure that the filter is capturing the most particles possible, making your air as clean and allergen-free as possible.  

Photo by Lorena on Unsplash