Category Archives for "Air Quality"

Power Outages and Air Quality

Power Outages and Air Quality

It’s not hard to imagine nowadays: hot weather, cold weather, storms, electrical grid system hacking, or just plain equipment failure are all reasons you could lose power to your house.  In that case, there are a number of things to consider and ways you can prepare. 

Generators:  If you are going to keep a generator as a backup power source, have a plan on where you will run it.  It’s NOT OK to run a gas-powered generator in an attached garage, or even next to an attached garage.   According to the U.S. Centers for Disease Control and Prevention, CO poisoning sends more than 20,000 Americans to the emergency room and kills upwards of 400 during a typical year. ( Gas-powered generators need to be placed at least 20 feet from the house, so that exhaust fumes can dissipate. To plan for this, make sure you can roll the generator to a safe operating place (preferably a fenced yard) and have a dedicated extension cord of the proper gauge wire to run to your home.  Inside your home, you should have a working CO monitor on each floor so that you can be alerted should the CO level rise. Change the batteries in the CO monitors once a year when you change smoke alarm batteries.  CO doesn’t even need open doors or windows to enter your home, so don’t circumvent these guidelines!  Other safety tips for generator operation: (

  • Keep fuel in approved safety cans
  • Be sure to shut off the generator and let it cool down before refueling
  • Don’t operate it in wet conditions; you can install a tarp or other temporary cover over it to keep it and the ground it’s standing on, dry.

Window screens:  Of course, ventilation sans electricity requires planning too.  It’s hard to keep the windows open for ventilation without proper-fitting screens.  If you don’t normally open the windows, now is the time to plan for having to do so. 

  1. Get windows working (here’s a video on how to unstick painted windows using a variety of tools and techniques). 
  2. If your windows are missing screens, plan to order at least one screen per side of the house, per floor.   You’ll want to allow cross-ventilation, so this means if you have a traditional four-sided, two-story house, you’ll need at least eight screens if you keep the interior doors open for cross-ventilation.  For bedrooms with multiple windows, it’s helpful to have an additional screen (2 total) in the bedroom so that you can get cross ventilation in the bedroom, even with the door closed.  Here’s a page that will help you order the right size screens and the right hardware.  Or, order adjustable window screens that will fit many different size windows.   
  3. For existing screens, consider having them re-screened in new material like AllergyGuard or PollenTec.  These screen materials are actually fine filters that block way more pollen, dust, and particles than traditional screens.  AllergyGuard boasts that it blocks particles from 0.3 to 10 microns, more than 69% of UV Light and 50% of Infrared Light, and over 95% of water and rain spray (allergyguard brochure). 

Cookstoves:  Electrical outages don’t necessarily mean eating cold canned food if you have a gas grill.  The grill could be standard or mini size ($89 at Amazon); the key is having the proper fuel ahead of time.  This mini grill is designed to run on small propane tanks (about 5 lb cylinders), but with a connective hose you can connect it to a larger cylinder.  As with any unvented gas appliance, it has to be placed outside!  Open carports with a cross-breeze are an ideal place to grill and stay protected from the weather.  Another option is to go old-school and have a small charcoal grill and bag of charcoal on hand.  Charcoal grilling takes a little practice; the key is building a hot bed of coals before starting to cook.  In order to eliminate the use of lighter fluid (the fumes of which go right into your food and cause photochemical smog), use a chimney starter like this one to get the coals nice and hot for a great grilled meal.  Alternatives to using a chimney starter are placing a charcoal briquet in each compartment of a cardboard egg carton, closing it and lighting each end of the carton, or placing wadded up newspaper below a pile of charcoal briquets, and lighting the newspaper.  These methods allow the cardboard or newspaper to burn slowly and allow time for the charcoal to catch fire.

Avoiding mold:  Without air conditioning and dehumidification, it's only a matter of time before mildew and mold will start to grow.  

  • Ventilation is the first key to prevention in this case.  If possible, open windows on opposite sides of the home to get cross-ventilation going.  
  • Use safe cleaning products that kill mold and odors: 
    • TotalClean uses iodine to safely kill mold and bacteria.  It even eliminates odors when sprayed in the air near trashcans and pet litter.
    • Concrobium Mold Control Spray uses a non-toxic trio of salts to kill mold and prevent future mold from growing.   You can spray it on draperies (test on a small area first), wood, and other furnishings to prevent mold when you’re not able to prevent high humidity. 

Staying cool:  Sleep is essential but it’s no fun trying to sleep when it’s hot.  Fans provide evaporative cooling (moving air that causes moisture to evaporate from your skin, taking heat with it).  Here are some innovative products to get cool and get some z’s:

  • Portable battery fan: This model from Treva is lightweight and runs an amazing 65 hours (source: camping review) on one set of 6 D-cell batteries.   It also has an AC adapter for use when the power is on.
  • Got an old-fashioned hot water bottle?  Fill it with one layer of ice cubes to chill down your bedding and keep you cool.  Or, strap small ice packs to your body’s pulse points (wrists, ankles, back of knees, armpits) using sports bandages or long socks.
  • Sleep out in the open.  Before modern air conditioning existed, the concept of a “sleeping porch” was used in the summer.  If it’s very hot, you can try sleeping on a covered porch with some protection from bugs.  You’ll need: 
    • A portable bed, cot or hammock so the bed is elevated off the floor for more ventilation
    • A mosquito net to protect from biting bugs:  there are many to choose from!  Try a single net for one person, or an outdoor screen house for several people

It’s an unpredictable world, so a little preparation will help you not to “sweat” the inconvenience of losing power.  Let us know what innovations you come up with to stay safe and cool during summer outages. 

Air-Sealing your Home

Air-Sealing your Home

Wow, the revelation that Ultrafine Particles (UFPs) from outdoor pollution can easily penetrate a home’s interior through cracks and leaks has really stirred our thinking.  Specifically, a 2018 study on UFPs from airport traffic during prevailing winds caused indoor pollutants to rise by 1.7 fold (170%), and HEPA filtration inside the homes only lowered them by 33%.  What does this mean?  Our homes are leaky, and no amount of indoor air filtration can keep up when outdoor pollutants are raging!  This could be wildfires, oil refineries, a major highway, a major port, or any heavy industry or power plant.  Basically, the only way to keep outdoor pollutants outside is to either seal the building envelope better, or use a positive pressure system where the inside of the building stays pressurized, so that airflow is always inside to outside.  

Before we get into the specifics, home builders in the past usually only concerned themselves with one barrier, a vapor barrier.  This was the felt paper, housewrap or other system installed under the cladding that prevented rain and moisture from entering the building.  A vapor barrier is not the same as an air barrier, and air barriers are much less common in residential and even commercial construction.  We’re talking about air barriers in this post, as air barriers are one way to block UFPs from entering your home.  

Here are some options for making an air barrier (sealing the building envelope):

From the outside: this is best accomplished during construction or major renovation:

  • Applying a membrane air barrier like Delta Vent SA over sheathing involves primer, tape and the barrier; this video shows how it is installed and the tape is preferred to caulking in preventing air leaks.

  • Spray Wrap MVP from Prosoco can be used as the primary air barrier over above-grade wall assemblies prepared with joint and seam filler.

From the inside: there are 3 ways to seal the inside: Before drywall, using the drywall itself as an air barrier, and after drywall. 

  • Before drywall: 

    • Use a product like Knauf Insulation EcoSeal, a waterbased elastomeric sealant.  First the exterior sheathing is installed and taped.  Then the sealant is applied to all interior seams and cracks with an airless sprayer at 1700 to 2200 psi, which really forces the sealant into any cracks. It fills gaps from 1/16” to ⅜”.  Here is a description of how it’s installed. 

    • OwensCorning EnergyComplete is a two part insulation and air-sealing system.  First a latex sealant is sprayed on the interior of sheathing (like Knauf Insulation Ecoseal), then the wall cavities are filled with either blown-in insulation (by using netting to retain the insulation) or with spray foam. 

    • You can apply an air barrier like Intello Plus (ceiling video, wall video, penetrations video) on the underside of ceiling joists, all along walls, sealing it to the subfloor.  Again, run a blower door test before installing drywall so that large leaks can be corrected. 

    • Use spray foam: spray foam is seen as a one stop shop that insulates AND seals, but it requires careful installation and checking through a blower-door test.  This article shows how an older house that is renovated with sprayfoam insulation can be surprisingly leaky.  The application of the foam is incredibly important in creating the seal, as small gaps between the spray foam and the back of the drywall can make a highway between penetrations.  The air barrier needs to be tested before the drywall is installed so that foam imperfections can be corrected.

    • Use AeroBarrier: This is a waterborne acrylic sealant that is sprayed into a pressurized space, using the pressure to guide the sealant into any cracks or crevices.  The process can be applied pre- or post-drywall with any type of insulation.

  • Using drywall: if you skip an air barrier membrane, you can use the drywall itself to make an air barrier.  The most problematic areas are the joints and penetrations, which can be addressed using the right materials.  You’ll need special electrical boxes, gasket material, expanding foam, flexible caulk and adhesive; here are 2 articles on what to consider and how to hang airtight drywall

  • After drywall: it’s not ideal, but you can still make major sealing improvements after your home is “finished”.   Start by doing a visual check for daylight or artificial lights around the door and window perimeters when they are closed.  You can use your hand or a candle to find air leaks and drafts as well.  Check under sinks and behind appliances like refrigerators and gas stoves for wall penetrations that have not been sealed.  Once you’ve sealed as much as you can with foam (be careful using expanding foam), caulk, and weatherstripping, call in an energy auditor to do a “blower door test” to see what you may be missing.  They should be able to tell you how leaky the home is in terms of “Air Changes per Hour” (ACH), and suggest and/or perform other remedies to lower the ACH, making the home tighter.

Because of the continued increase in interest for air-sealing homes and businesses, there is an Air Barrier Association of America (  The association is “committed to educating the public about air barrier systems and developing a professional air barrier specialty trade and industry dedicated to the installation of effective air barrier systems in buildings on a nationwide scale.”  Here are some of the resources they have:

  • Here are some of the systems they’ve tested for air barriers.

  • You can search for a specialist in your area here

  • Courses for installers, auditors, and whole building airtightness technicians (with applicable fees but open for anyone to take)

Air-sealing your ducts for better air quality and energy savings

Air-sealing your ducts for better air quality and energy savings 

In our post “How does indoor air pressure affect ventilation and air quality?” we show a photo of a room being aerosol sealed from the inside out.  This is a great way of closing up the small leaks (up to ½” diameter) that are overlooked by design flaws or construction crews, in order to seal the home’s thermal barrier before finish work on the home is completed.  Here’s how this innovation started: duct sealing.

Before rooms were sealed from the inside out by aerosol sealant, the process was developed for air ducts in 1993.  In one case study by AeroSeal, the innovator and major supplier for this technology, a homeowner had her ductwork expanded to cover previously unserved areas of her home.  After the new ductwork was installed, the system was pressure-tested and it was discovered that air of about 919 CFM (cubic feet per minute) was leaking through the ducts, which is the equivalent volume of about 551 refrigerators per hour(!).  According to, “about 20 to 30 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts.”  (To put this in perspective, the average system is 3.5 tons.  A system is required to have 400 cfm per ton of air across the evaporator coil for cooling, thereby 1400 cfm is the normal flow of the average system.  Twenty percent (280 cfm) to thirty percent (420 cfm) would normally leak from the ducts, so this homeowner either had a much larger home, or exceptionally leaky ducts.  In any case, after sealing the ductwork, a 91% reduction in leakage was realized.  Consequently her sinus issues were relieved and she felt more comfort in the home.  The system was previously drawing in dust and contaminants from outside the home and recirculating them in the HVAC system; apparently this problem was relieved by sealing the ducts.

The following diagram shows how air leaks into and out of ductwork (

The home is in heating mode shown by the orange ductwork coming out of the furnace in the bottom right.  Ductwork farther from the furnace turns blue (cooler) because pressurized, heated air is leaking from the ducts into the crawlspace and void spaces, before it even gets to to the farthest room.  For air quality purposes, the most important part of the system is the return areas, in the ductwork in the attic of this house.  Because the air pressure inside return ducts is negative (it is being “sucked” or drawn back to the furnace by the fan), any leaks in this area will cause dusty, unconditioned air from the attic or voids into the ductwork (see green arrows entering the ductwork in the top of the picture).  This is one major cause of excessive dust and poor air quality in many homes.  Even more leaky are the ducts in many multi family homes and apartment buildings.  AeroSeal has been successfully used in these buildings since 2007-8.  

The sealant used by AeroSeal is a “water-soluble organic compound” (AeroSeal FAQs) with an extremely low concentration of VOCs.  The sealant smells like Elmer’s glue when wet, but dries to be odorless. The safety data sheet reveals it to be a “vinyl acetate copolymer” (35% max weight) and “vinyl acetate monomer” (<0.01% when dried).  In accordance with California Prop 65, the product “does not contain any chemicals known to the State of California to cause cancer, birth, defects, or other reproductive harm.”  According to the EPA, vinyl acetate definitely has exposure limits due to irritation of upper respiratory tract as a result of acute or chronic exposure.  Due to this information, it’s possible that very sensitive individuals could have a reaction with the dried substance in their ducts, so it may be wise to ask for samples before it’s applied in the home of sensitive individuals. 

Aeroseal is not the only duct-sealing product on the market.  Here are some other options:

  • Aluminum duct tape is available online and at most home improvement stores and can be used by anyone.  

  • Ductwork mastic should be applied over the aluminum duct tape. It gives extra strength to the seal and encloses any seams of the tape.  It’s applied by paint brush and is usually water soluble (soap and water cleanup).

  • Spray Mastic products: These are typically products for professionals because of the spray equipment needed to apply them. 

    • Spray-Seal by Carlisle is a sealant applied to the exterior of ducts (especially hard ductwork) manually either after fabrication or as an upgrade to existing ductwork. 

    • PROseal Spray by Ductmate Industries Inc. is a sprayable mastic sealer which is also applied by professional spray equipment.  

    • Duct-EZ is a water-based zero-VOC mastic that is not only used to seal ductwork; it is also used to seal cracks in your foundation or basement to reduce seepage of radon into your home.  

Since dust is a major contributor to indoor air pollution, the dust may indeed be coming from the attics and crawlspace, and/or directly from the outside through building envelope cracks and crevices.  Before contracting for a duct-sealing service, it would be wise to have an energy audit on your home performed in order to discover the most economical ways to seal the largest leaks.  

Photo by Tekton on Unsplash

What are ultrafine particles and where do they come from?

What are ultrafine particles and where do they come from? 

In our post “Which particles can get captured by a filter or by my lungs?”, we mentioned ultrafine particles, which are classified to be 0.1 micron or less in diameter.  They are called UFPs (ultrafine particles) or PM0.1 (Particulate matter 0.1 microns), and are dangerous to our bodies in a different way than PM2.5 (Particulate matter 2.5 microns) , because they can migrate from the lungs or respiratory pathways to the rest of our bodies.  Their movements and concentrations are also different.  Learning about them is a good defense for avoiding them, though, so here’s some of what we know.

  • PM2.5 consists of a mixture of particles of varying sizes from a variety of sources, with the most numerous particles by count usually falling within the ultrafine size range (<100 nm).  
  • UFPs are mainly composed of organic compounds, elemental carbon, trace metal oxides, sulfates, and nitrate ions (2012 and 2016 studies). 
  • Among the sources of emission, heavy industries are considered one of the largest anthropogenic sources of trace metals (2012, 2014 and 2017 studies)
  • UFPs are unstable.  They have positive, negative and neutral charges,  and become larger particles through coagulation (when two or more particles combine) and condensation (when additional vapors can condense on the particles) (Jan 2022 overview). 

UFPs can be emitted by a number of sources.  

Source: overview study of UFPs

Since Natural Sources are largely not controllable, let’s focus on the anthropogenic sources (originating from human activity). 

Vehicular, aerial and sea traffic:

Airports: it’s estimated that in the United States ∼40 million people live near 89 major airports (i.e., within areas with ≥45 dB noise levels near airports) (study).

Aircraft exhaust is the #1 pollutant at major airports, and neighborhoods surrounding the airports even 10 miles away have higher ultrafine pollution levels.  According to a 2014 study, the “level of pollution at LAX (Los Angeles International Airport) was equivalent to the emissions generated by nearly 500 vehicles stalled in freeway traffic every day.”  Another study in 2018 in the Boston area measured particle numbers (PN) indoors and outdoors.  PN overall indoors was compared during times of impact-sector winds (during prevailing NW or SW winds) to calmer conditions; during impact-sector winds, the indoor measurements were about 1.7 times that of calm conditions.  We know that particles infiltrate homes via cracks in the building envelope, open windows, or forced-air ventilation, and this was shown through the study because outdoors and indoor PN levels usually increased and decreased in tandem, except for indoor events like cooking or cleaning.  Unlike road emissions, aviation emissions do not dissipate with higher windspeeds because of the buoyant nature of the aviation emissions.  This is the reason that some ultrafine particles, like wildfire smoke, can be transported in upper-atmosphere winds for thousands of miles.  Interestingly, significantly higher UFP emission per kg fuel burned resulted under landing conditions as compared to takeoff conditions. (2021 study)

HEPA filtration inside the homes helped somewhat; it lowered indoor PN by approximately 33%.  This is good, however, it didn’t have the same effect as lower number of flights or no impact-sector winds.  This causes us at HypoAir to continue recommending sealing homes to the best of our ability, and using controlled fresh-air ventilation for homes (via filters).  Ultrafine particles from airports are not currently regulated by the EPA, so we need to protect against them!

Vehicle exhaust: In many urban areas, vehicle exhaust is a major health concern. The following pictorial representation is found in the study “Chemical Composition of Quasi-ultrafine Particles and their Sources in Elderly Residences of São Paulo Megacity

In urban areas with both aircraft and ground vehicle pollution, vehicle exhaust can be identified by larger particle size and higher BC concentration. (2021 study). 

Likewise, roadway emissions can be characterized by the fuel type, lubricants used, thermodynamic conditions, ignition technology, and the number of vehicles running.  This is why large cities have performed emission inventories in order to reduce particulates in certain ranges by certain types of vehicles.  National and local governments have devised three categories of strategies to control PM emissions: (1) fuel-based strategies, which include reducing sulfur levels; (2) engine-based strategies, which could alter combustion to reduce emissions; and (3) exhaust emission control strategies, which include the use of modern technologies, such as DOCs, diesel particulate filters (DPFs), and SCR catalysts, focusing on reducing emissions after combustion has taken place but before they leave the tailpipe. (2020 article).  New engines, paradoxically, emit more UFPs than older engines (1996 Health Effects Institute), but with these exhaust emission control strategies, UFPs can be captured before they are released.

Marine traffic: According to, 76% of all trade in the US involves some sort of marine transportation, and marine transportation touches 90% of all trade internationally.  Barges are extremely efficient transporters; what other mode can transport a ton of cargo 647 miles on 1 gallon of fuel?  In comparison, trains move 1 ton at 477 miles per gallon, and trucks at 145 miles per gallon. (2017 article).  However, the sheer number of tons of cargo moved on ships and barges necessitates huge quantities of fuel and emissions.  The International Maritime Organization (IMO) mandated lower sulfur contents in marine fuels beginning in 2020, at max 0.5% sulfur down from 3.5% previously for heavy fuel oil (HFO).  This cap caused many ships to start using intermediate fuel oil (IFO) or other lighter fuels instead of HFO.  The sulfur cap is a step in the right direction for less sulfur in the environment, but it was not expected to reduce UFPs (in terms of Particle Number or PN) from shipping sources.  The total output of PN from marine shipping in 2016 was similar to the total anthropogenic emissions in continental areas.   Thus, marine traffic is a significant source of UFPs (2021 Environmental Science & Technology article).

A third major source of outdoor anthropogenic UFPs is from coal-fired power plants, which produce emissions that are particularly rich in metals. You can access a map of US power plants here (gas, oil and coal), that gives type of fuels, emissions, and demographic information of the surrounding area.   Many plants may filter their emissions to meet standards, however UFPs can form outside of the stack when SVOCs condense (gasses turn into solids and thus bypass the filter). (2020 article) This process is called nucleation.  The most persistent UFP sources in the low atmosphere near the surface are modern technology fossil fuel-burning power stations, refineries, and smelters, according to a 2018 study

A fourth major source of outdoor UFPs is from wildfire smoke and controlled burns, which can vary significantly depending on the type of wood burned and its moisture content.  Wildfires can also smolder for a long time after being “extinguished”, and this smoke contributes significantly to the total wildfire emissions. 

Indoor UFPs are a combination of what has leaked into the house from the outdoors, and what is generated indoors.  Cooking and cleaning are large contributors, as well as candles, incense, smoking and e-cigarettes, and (in unconditioned climates) mosquito coils.  The use of e-cigarettes by children and young adults is unfortunate because their lungs are more susceptible to damage from UFPs.  Also, if you have a laser printer, it is surprisingly one of the major contributors to UFPs in offices (and homes!).  

The effects and 

Toxicological effects from exposure to UFPs; Jan 2022 overview

Here is what happens when our bodies encounter UFPs.  They are normally inhaled (effects via mucous membranes, skin and eyes are much smaller). The larger particles (10 microns and larger) can be trapped and removed via the mucous system, but smaller particles (2.5 microns and smaller) may be trapped in the alveoli and terminal bronchioles.   UFPs go into the deepest parts of the lung, and the body’s cellular defense system is activated.  This includes macrophages, various cytokines, chemotoxins and leukocytes, including neutrophils. Some of these are involved in the body’s inflammatory response, which not only damages the invading substance, but is also detrimental to the body in chronic doses.  

The UFPs can translocate to other organs such as the brain, liver, kidneys, and because they are fat-soluable, also deposit in adipose tissue. The body’s production of oxidizing species places oxidative stress on the body, which can cause damages to the DNA and mRNA, and lead to cancer.  Even transgenerational changes to DNA can (occur through inheritance!  

The toxicity of UFPs depends on a number of factors, including:  

  • The age and health of the person affected (children are most affected, followed by the elderly and pregnant women). 
  • The emission source, which determines the makeup, characteristics, size and concentration of the pollutants.  For example, black carbon (BC) is one combustion pollutant made up of PM2.5 and UFPs, but it is more harmful than other PM2.5 because of the body’s inflammatory response to it.  Black carbon can also adsorb other toxins before it is inhaled, like VOCs and PAHs (polycyclic aromatic hydrocarbons).  One study found that the smaller the particle size, the greater the inflammatory effects in the lungs, and the greater the DNA damage.  Another study found a positive correlation between the concentration of UFPs from motorcycle exhaust and the physical of damage to mice kidneys (neurological effects, memory loss,  behavioral problems and changes in brain tissues are other effects). 

With all the sources inside and outside, it seems that UFPs are unavoidable in daily life!  They are everywhere, but here are our top tips for keeping them out of your home and your body:

  1. Seal up your home as tightly as possible, and use controlled fresh air ventilation through a MERV 13 filter* (see chart below) and your home’s HVAC system.  Balanced ventilation (as opposed to negative pressure ventilation) has less chance of suctioning combustion exhaust from gas appliances such as gas dryers, water heaters and furnaces.  
  2. In addition, use a HEPA filter in your home to capture UFPs that are generated in the home or slip past the ventilation filter. 
  3. Bipolar Ionizers like those in HypoAir’s Germ Defender, Air Angel or Whole-Home Polar Ionizer help to cluster ultrafine particles into larger particles that can fall out of the air or be captured in a HEPA filter.
  4. Use stovetop ventilation during and after cooking and bathroom ventilation during and after showering.
  5. Don’t smoke or vape (use e-cigarettes).
  6. Use a HEPA mask (outdoors or in a separate ventilated building if possible) during high-risk activities like welding, spray painting, sanding or woodburning and 3D printers. 
  7. Don’t allow vehicles or gas engines like generators or lawn mowers to idle in the garage.  
  8. If you move, reconsider locations with high UFPs such as downwind of airports, refineries, power plants, bus stations, major highways, etc. 

*Here is the reason we recommend MERV 13 for ventilation filters:  it increases capture of small particles to include that of smog, tobacco smoke, and cooking fumes. 

Above diagram from

Photo by Kunj Parekh on Unsplash

Which particles can get captured by a filter or by my lungs?

Which particles can get captured by a filter or by my lungs?

This is an incredibly important and somewhat complicated question.  I want to present the following graphic, which shows relative particle size.  I’d say it’s pretty surprising how large our hair is and how small those bacteria, smoke particles and viruses are, right?  The “µm” stands for micrometers, which is one-millionth of a meter.  Micrometers are also called “microns”, so the human hair is 50-180 microns.

In our FAQ on “What is HEPA?”, we explored how filters actually trap contaminants like these.  In order to start answering our original question, let’s review that!

“Sieving” is the most simple way a filter “strains” out the particles that are larger than the openings between the fibers of the filter.  

                  (image from

Then, there are three types of motion that particles experience in a stream of air, such as the airstream being drawn through a filter.  Filter design actually takes advantage of the size of particles and the way they move through the air, in order to capture them.  

  • Obviously, some particles are larger than others.  Inertia acts on larger particles by causing them to continue in their original path of motion when entering the filter, thus colliding directly into fibers instead of sweeping around them with the accompanying airflow.  Particles 0.3 micron and larger (coronavirus size and larger) are affected by inertia. 

                (image from

  • Air is made up of all kinds of molecules and particles, which are getting thrown about in erratic ways by collision with one another.  This is called Brownian motion.  Taking Brownian motion into consideration is filtering by diffusion, which occurs when smaller particles travel in an erratic fashion through the airflow and are impeded by fibers.  The particles trapped by diffusion are typically smaller than 0.1 micron.

                         (image from

  • In direct interception, a particle follows the airstream but travels closer than its radius to the fiber, “brushing” it and becoming stuck.  This can happen for many different sizes of particles and just depends on where they are in the airstream relative to the fibers.  

                    (image from

So there you have it– four ways a filter uses to capture particles.  Interestingly, because of the gap between inertia and diffusion, particles around 0.3 microns in diameter are the most difficult to filter out of the air, because they are least affected by these methods.   This is called the most penetrating particle size (MPPS)--the size that is most likely to slip through the filter.  

HEPA filters are rated on their ability to remove this size particle—0.3 microns.   They do so with greater than 99.95% efficiency.   There are 2 ratings of HEPA: H13, which removes at least 99.95% of 0.3 micron particles, and H14, which removes at least 99.995% of 0.3 micron particles.  

Without a HEPA filter in your home, you are probably relying on furnace filters of various lower filtration ratings.  That means that more particles are getting through the filter, and remaining in the air for you to breathe.  Yikes!  Particles of 10 microns or less can be inhaled, and particles of 2.5 microns or less are more likely to deposit deep in the lungs.  (California Air Resource Board).  This size of particle is extremely lightweight, and once it’s in your lungs, it can move all the into the deepest part of your lungs and lodge there.  Without filters to capture particles from the air, unfortunately your airway and lungs will act as filters.  Here is how (Canadian Center for Health and Occupational Safety):

  • The respiratory system can be divided into upper and lower regions.  The upper region starts at the nose and mouth, and goes down to the vocal cords in the larynx. The lower region starts at the larynx and extends through the trachea all the way to the bronchioles and aveoli (smallest air sacs).

  • Particles 10 microns and larger are most likely to lodge in the upper respiratory region by inertia (also called impaction), because in this region, air is flowing at a higher velocities and during the twists and turns particles tend to continue in their original direction and “impact” a wall of the airway and stick there.

  • Interception is likely to occur with fibers, like asbestos fibers.  In the range of 1 micron in diameter and 200 microns in length, if one end brushes an airway wall, it will lodge there.  These can make it into the bronchial tree.

  • Sedimentation occurs when particles larger than 0.5 microns loose their momentum and gravity takes over, causing the particles to settle in the bronchi and bronchioles.  

  • For particles smaller than 0.5 microns, diffusion is in effect (Brownian motion).  This can happen in the small airways and alveoli, when air has virtually slowed to stillness.  

  • Although the mucous lining of our respiratory tracts was designed to clear airways by moving it up and out of the respiratory system, it does not always function well in older and diseased people, and the sheer number of ultrafine particles can clog airways. 

Fine particles (2.5 microns down to 0.1 micron) and ultrafine particles (0.1 micron and smaller) are shown to cause inflammation and inflammatory diseases.  Ultrafine particles can migrate from the alveoli to the bloodstream and to other organs, resulting in delayed sicknesses such as reactions to vehicular pollution, welding fumes and burning trash.  The danger of ultrafine particles is not just their size and number (much greater numbers PM2.5), it is also their charge, which can adsorb toxic chemicals onto their surface.    Fine particles have been shown to cause cardiovascular disease; they travel up the olfactory nerves to the brain; they are inhaled by electronic cigarettes, and have been shown to increase risk for hypertension and diabetes and cause cancer (animal studies) . (study)

For all these reasons, a HEPA filter is a great addition to your home, vacuum, and even a mask when you are performing high-risk activities like welding, spraying paint, or caring for a sick relative, so that the filter will do the work instead of your lungs and body!

Photo by Joshua Newton on Unsplash

How to live with minimal AC and maximum ventilation

How to live with minimal AC and maximum ventilation

For decades (five to be exact), home design focus has been on sealing homes in order to reduce energy costs of heating and cooling.  Such energy efficiency has come at a price of air quality, because unlike, say, water, air cannot be “recycled” over and over without detriment.  Carbon dioxide concentrations will increase naturally just from breathing in and out, and toxins build up from emissions from the building itself and the products we use in it.  Humidity either builds up from water leaks and water use, or decreases from use of forced air heating.  

Is it time to advocate for more “leaky” homes?  Well, yes….but controlled leaks are key!  The leaks I’m talking about are ventilation with fresh air in a controlled way.

Here at HypoAir we often recommend adding more ventilation from outside to dilute the air in our homes, so it’s constantly on my mind: how do I get more ventilation during the hot months of the year?  We tell customers that it’s ok to open windows when the outside air is relatively clear of pollution, but many times it still has dust, pollen and smaller particles, so that presents a problem!

While researching this topic, I found a statement that sums up the problem:  

“Every new system installed today should have a Fresh Air Intake. It should not be optional, it should be mandatory. State laws do not force the issues, but health concerns do. Products that we use in our homes have Volatile Organic Compounds (VOCs) that put out gasses as they age. Without a Fresh Air Intake, these VOCs can build up and cause allergic reactions, asthmatic symptoms, and can require treatment with medicine to compensate for the contaminated air. The medical industry does not recognize contaminated air as a medical condition. The reason is, they can’t measure that when you go for treatment. They can only address the problem.

Generally, about 5-10% outside air is desirable. If you don’t have fresh air inside your system, should you add it? The answer is YES, especially if you're doing equipment replacement.” (Texas HVAC company)

Now, which new products aimed at cooling also increase ventilation?  I focused on whole home ventilation in a previous post; this one is more geared toward single-room or window units.

The EcoBreeze 2 is a smart window fan that takes outside air, filters it, and delivers it inside as clean, fresh air.  It has sensors: if the outdoor air is more hot or humid than indoors, then it shuts down and lets your A/C take over.  This is particularly useful in climates where outside ventilation is cool and dry, such as in the northern US. It retails for $229 and has optional MERV 13 filters for replacement (it comes with a MERV 8 filter).

Here’s what to do if you already have a window fan, in order to get cross-ventilation, which is very useful because with only 1 window fan, you’re not really cooling optimally unless you have another window open to allow the hotter air to escape.  

  1. On the hot or unshaded side of your home or room, install any standard window fan that you can seal effectively to your window, but set it to “exhaust” mode (pulling air out of the room).
  2. On the opposite (shaded) side of the home or room, install Safeguard Window Filters ($51 for the large size accommodates windows from 24-44” wide).  In this way, you are pulling cool air into the room through the filters, and exhausting it out through the fan.  The filters can be vacuumed several times before replacing the inserts (see for the replacement filters).

Now, if your outside air is too hot or humid for adding a lot of ventilation, you can still use your window A/C in conjunction with a Safeguard Window Filter.  The window filter does not allow a lot of air to pass through (unlike a plain screen, but you can add the ventilation needed and let the AC do the cooling and dehumidification. 

If you want to replicate this on the scale of your whole house, many HVAC companies recommend QuietCool Whole House Fans.  I grew up with a whole house fan, but this one will not create a rumbling noise, so you can leave it running all night (hence its name).  Using Safeguard Window Filters in conjunction with the whole house fan will insure that your home is not filled with bugs, dust and pollen as it pulls in air from outside. What a relief to breathe in fresh air, especially while you sleep!

If any engineers out there are reading this, I’m still looking for:

  • a window heat pump unit (heating and cooling capacity)
  • with inverter technology (to save energy and provide constant temperature and humidity), and
  • a filtered ventilation component, like the EcoBreeze 2, and
  • a pollution monitor on the outside to shut off intake at times of high pollution   
  • Oh–and I like how new over-the-sill designs do not obstruct the window view.  

Am I asking too much?  I don’t think so–this is 2022–let us know what you come up with!

Photo by Olia Nayda on Unsplash

Increasing our bodies’ resistance to mold–naturally

Increasing our bodies’ resistance to mold--naturally

There's no "silver bullet", but regarding exposure to mold, there’s a lot we can control, like humidity, water leaks that can be stopped and remediated, air purifiers, etc. Sometimes, though, there are things we just can’t control, like having a new work assignment in a moldy area, or having a scrape (literally) that infects us with mold.   That’s what happened to a young man traveling in Costa Rica, who developed a lesion in his brain due to a type of black mold after scraping his arm on a bike ride.  In India, doctors are facing an unprecedented spike in mucormycosis, an infection from another type of mold species that is very prevalent in the hot, humid country.  Indiscriminate use of steroids to stop inflammation from the virus that caused COVID-19 causes some patients to have weakened immune systems, making them susceptible to infestation of Mucorales, the group of fungi that includes molds responsible for mucormycosis. (Science News)  With Mucorales, the fungi tend to thrive in diabetics because of elevated blood sugar levels, which turn the blood more acidic, creating an ideal environment for it to spread.  Unfortunately, the virus that causes COVID-19 also damages the beta cell of the pancreas, decreasing insulin production needed to check high blood sugar.   

It doesn’t need to be far from home, as this can happen in your backyard.  Candida auris has been identified as a new global threat; it’s a type of fungus that is resistant to 2 out of 3 classes of antifungal drugs.  

Here is what we’re seeing cause susceptibility to fungi:

  • Steroid medications, including artificial corticosteroids, which dampen immune function by lowering the number of lymphocytes 
  • Stress releases natural corticosteroid in our bodies (decreasing immune function as above) and stress also alters a number of bodily functions like digestion activity, blood pressure, blood cholesterol levels, all of which lead to an increased risk of disease (
  • High blood sugar from diet, disease or inadequate medication management
  • Other causes of more acidic blood: respiratory acidosis is the body’s response to having too much carbon dioxide in the blood (a common cause would be sleep apnea), metabolic acidosis which includes ketoacidosis, lactic acidosis, renal tubular acidosis and hyperchloremic acidosis (webMD)
  • Pre-existing conditions such as AIDS: “According to the Centers for Disease Control and Prevention (CDC), fungi are among the leading causes of opportunistic infections affecting patients with HIV/AIDS [16].” (study)

The good news is that fungi have weaknesses we can exploit.  Here are some of them:

  1. Copper: fungus has a small window of tolerable copper levels.  “the human immune system utilizes both copper toxicity and copper starvation in responding to fungal infections. “(Valeria Culotta, PhD) Drinking water stored in copper vessels may provide the excess copper needed to kill many pathogens (
  2. Iodine: A lack of iodine has been shown to cause many different diseases and symptoms, including endemic goiter, hypothyroidism, cretinism, decreased fertility rate, increased infant mortality, and mental retardation (article). On the other hand, iodine has been shown to cure toenail fungus (study), and iodine is is rapidly effective against viruses, bacteria (both Gram negative and Gram positive), fungi and spores( However, not all iodine preparations have high- germicidal properties.  Molecular iodine (I2) is the form that kills fungus and molds most quickly. Here are the positives about a new formulation of iodine, ioRinse
  • Does not stain, unlike previous formulations of povidone-iodine
  • does not induce resistance development in targeted microorganisms
  • substantivity (ongoing residual effect) of iodine for up to 72 hours is well documented.
  • Safe for chronic use as a mouthwash
  • Affordable
  • Molecular iodine is also available in a Nasal Spray (ioMist) to protect sinus passages.
  1. Zinc is a metal that is needed for a healthy body and immune system, but it can be stolen by pathogenic fungi such as mold.  Our bodies attempt to withhold this essential vitamin from pathogens (a process called nutritional immunity), but certain pathogens have evolved highly sophisticated methods of acquiring it from hosts anyway. (study)  A 2017 US study carried out over six weeks found that taking just 4mg extra of zinc a day made a major difference to the health of cells, which in turn makes your body better able to fight infections and diseases. The team concluded that zinc reduces ‘oxidative stress and damage to DNA’ that helps protect against chronic diseases.
  1. Glutathione: When our bodies are exposed to harmful fungus, they increase production of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS).  ROS/RNS are helpful in that they signal an invasion of the body and trigger more immune responses, but they also can damage lipids, proteins and DNA (study), and overwhelm the natural antioxidant capacity of our cells, causing the imbalance that is known as oxidative stress. Normally ROS levels are kept in balance with antioxidants in our cells, which is known as cell redox homeostasis, but in the presence of pathogens, ROS increases dramatically, causing inflammation and other potentially damaging symptoms.  Glutathione (GSH), made of the three amino acids cysteine, glutamate, and glycine, is an important antioxidant in our bodies (  Our glutathione levels decrease naturally as we get older, but more acutely during diseases such as cancer, HIV, or Parkinson’s disease.  In a Korean study, it was shown that glutathione significantly increased a cell’s chances of surviving exposure to large amounts of ROS like hydrogen peroxide (H2O2).  Low levels of glutathione peroxidase are also coincident with conditions like vitiligo, multiple sclerosis, and Type 2 diabetes. (  Therefore, supplementing with this “superhero” antioxidant can significantly improve our outcome when faced with mycotoxins.  Here are some ways to supplement:
  • Intravenous (IV) glutathione is the quickest and most effective form of supplementation, but its availability to the public is limited.  
  • Although many companies offer glutathione in oral form, it’s generally not effective in raising free glutathione in the blood because digestive enzymes break it down into its three components.  Therefore,  two alternative forms of glutathione that translate to higher glutathione levels in the blood:
    • liposome-encapsulated glutathione, or
    • s-acetyl glutathione: this has been shown to have similar results to IV glutathione (  
  • Whey protein contains free fatty acids that actually inhibit growth of C. albicans (study). C. albicans is the most prevalent form of fungal infections in people (, and knowing this, supplementation with a whey protein from grass-fed cows can be a good way to increase resistance to certain fungi (  
  1. Iron: Iron is essential for both humans to grow.  Iron is needed to produce red blood cells and hormones, as well as maintain our immune system response, particularly a level of lymphocytes (scientific article). Here is the conundrum however: fungus also needs iron, and will steal iron from our bodies or scavenge excess iron if it is supplemented.  In healthy people, iron supplements are a good way to make sure we have the iron we need.  (If normal iron supplements upset your stomach, try a “slow-release” formula). However, if you are diabetic, undergoing chemotherapy, or have any other major illness, you may want to consult your doctor before adding an iron supplement, to make sure that it does not feed an invasive pathogen like mucorales, which is particularly disfiguring and deadly in immune-compromised patients. 
  2. Healthy gut:  According to, “A healthy gut contains healthy bacteria and immune cells that ward off infectious agents like bacteria, viruses and fungi.” In addition, a healthy gut microbiome trains immune cells for guarding the brain:  scientists have discovered that certain plasma cells from the intestines migrate to the brain, where they stand guard to release IgA antibodies to block the entry of pathogens to the brain. (Science News)  How to maintain a healthy gut?  This article discusses some excellent ways to maintain a healthy gut microbiome. 
  3. Getting adequate sleep: During sleep, our bodies produce cytokines and T-cells, both of which are important to our immune response.  We’ve discussed how to get the most of your sleep time in a previous post, and this article from reviews the ways you can promote quality sleep.  

We’ve got the power to reduce the chance of acquiring nasty and life-threatening fungal infections, even in this world of ever-increasing dangerous microbes.  I hope this article gave you some new insights on some weapons in our immunity arsenal.

Photo by zibik on Unsplash

How to clean your car’s HVAC and interior to keep away mold!

How to clean your car’s HVAC and interior to keep away mold!

As I write this, we’re coming into another air conditioning season in the southeast US, which means air conditioning not only at home, but in your car.  Vehicles are so susceptible to mold ingress, because of where we drive (through dust, mud, and pollen), where they are parked (whether it’s outdoors in blazing hot driveways or indoors in damp garages), and their design (carpeting everywhere!  Air conditioning filters that hardly ever get changed!)  Whether or not you smell that musty moldy smell when you get in the car or turn on the A/C, now is the time to deal with mold before it deals with you.

Just like your home’s HVAC system, it’s important to maintain your car’s HVAC system for your health.  Here is a great article on cleaning the evaporator coils in your car.  This method is very non-invasive, and includes tips if any mold smells do not go away.   The antimicrobial agent they recommend is called Nutribiotic. Nutribiotic is a grapefruit seed extract (GSE) which is highly acidic and microbial at full concentration (be very careful mixing and using it!) but can be diluted to use as a coil cleaner.  Please note that using a commercial coil cleaner is not recommended because the residues can add many VOCs to the air you breathe, which may not go away for some time!  

When cleaning the HVAC system, be sure to replace the cabin air filter, which keeps a lot of dust and pollen out of the car.   Some older models don’t have a cabin air filter (commonly in pre-1996 vehicles and even as late as my 1999 Suburban), in which case you can even get creative and make one!  (For those of us who aren’t super-familiar with cars, note that the cabin air filter is different from the air intake filter.  The first one filters the air conditioning system, while the second one filters the air going into the engine, which is not what we’re talking about here.)

We’re working from top to bottom, and next come the seats.  Cloth seats will probably hold more dust and mold than vinyl or leather seats, because they are permeable and allow liquids and dust to pass through and stay in the foam beneath.  With any liquid cleaner you use, you should definitely use an extractor.  Whether it’s a carpet cleaning machine, or a simple wet-dry vacuum, you need a way to get the liquid back out of the carpet, or mold can set in after you just cleaned it!  If you live in a populated area, either one (carpet cleaner or wet/dry vac) should be available on places like Facebook marketplace for about $40. One more tip: only clean your car’s upholstery and carpet on a bright sunny day outside, or in a heated garage!  You’ll need the benefit of ventilation and heat to get the fibers completely dry. 

Now, what to use as a cleaner?  One of the most popular carpet cleaners in the supermarket is Resolve, and RESOLVE Professional Spot and Stain Carpet Cleaner earned an “F” grade from the Environmental Working Group (EWG), an organization dedicated to evaluating the safety of consumer products!  There is a better way. 

  • Our new Total Clean spray is like a Swiss Army knife that cleans solid and porous surfaces well!  Use it at normal strength (1:7 parts concentrate to water) for non-stained carpet and upholstery, or double or triple strength (1:3 or 1:1 parts concentrate to water) for stains.  Normal strength TotalClean is great for vinyl and leather surfaces, as well as any hard surfaces such as dashboards, gauges and steering wheels, being sure to wipe it away quickly with a clean dry towel. 
  • Most “homemade” carpet cleaners call for a mixture of vinegar, baking soda and water in various proportions.  I really like this one, which adds in (non-toxic) dish soap.  If you are using a simple wet-dry vacuum, use the cleaner in a spray bottle, agitate any problem areas or stains with a scrub brush, and follow with the vacuum to get the liquid out.  If you are using the carpet cleaner machine, follow manufacturer’s directions.  In either case, make sure to use the liquid sparingly!  Too much liquid going in (especially on cushioned areas) increases the likelihood that it will not all come out with the vacuum.  I advise taking out a car mat to clean first, to assess the suction power of your vacuum or cleaning machine.  After several vacuum passes, the carpet should only feel damp, not soaking wet.  (From experience, I once wetted down a large area of my sofa before discovering that the suction of the cleaning machine attachment wasn’t working!  I was blessed to have a wet-dry vac available as a backup). 

Unless you have those nifty molded floor mats that capture the dirt and water that you track in, there is going to be dirt and there is going to be mold in the floor of your car.  Mold thrives in dirt and moisture.  Even if the carpet is not stained, it’s a great idea to clean the carpet at least once a year to remove mold and dirt.

Now that you’ve removed the sources of mold in your car, you can add some non-toxic scents back into it.  Here is a video with 6 different ways to make non-toxic car air fresheners using essential oils and different items to hold the scent. (The speaker may be a bit difficult to understand, but the sachets she mentioned are muslin drawstring bags and the last item she sprayed on was wool felt–a very natural, absorbent material).  If you don’t have the time to make your own, just order some vent clips or auto stix from Enviroscents, a company that does not use toxic materials in any of their products.

Ahhh!  It may be a bit of work to achieve, but who doesn’t like the smell of a clean, fresh car?  For as much time as we spend in them, your health is worth the effort!

Face Masks: the air filters we never thought we’d be wearing

Face Masks: the air filters we never thought we’d be wearing

Pre-pandemic, I grudgingly used face masks to protect from dust and allergens, like when mowing the lawn kicked up dust, or sanding wood projects filled the air outside with dust.  I knew when I should have worn one…usually by a raging sinus headache the next morning.  Nowadays, concerns for our own or others’ health mandates wearing masks in public settings for a large portion of the year.  But–what are the risks versus rewards of masks?  What do they really do for us?

The CDC has plenty of guidelines about masks, including that masking is a “critical public health tool for preventing spread of COVID-19”.  Masks are made to contain droplets you breathe, sneeze or cough out, and provide some protection from droplets from others.  Respirators are meant to filter the air you breathe as well as contain your droplets.  It’s not hard to tell which are masks and which are respirators, according to how loosely they fit, and the materials and style in which they are made.  The CDC outlines the four types of masks and respirators: 

  • Cloth: they should fit well, have a nose wire, and you should not be able to see light through the fabric.  Regulations now prohibit any “exhalation valves” that would allow droplets to escape.  Lots of innovators have offered new designs for cloth masks, even ones that filter more N95 respirators.  Most cloth masks are washable, and wearers need to have clean replacements ready if the mask gets wet or dirty.  Wet masks do not filter properly and increase the leaks around the edges of the mask. 

  • Procedure masks, or “medical masks” are typically the light blue variety that are now readily available in most stores.  They are made from “non-woven” material that can be mass-produced and sold inexpensively so that dirty or wet masks can be disposed of and replaced with a clean one.  Make sure to wear them with the blue side out (or if your mask is totally white, with the soft side toward your face) and to pinch the nose wire to fit snugly.  Cloth masks should be disposed of when they are wet or dirty.

  • Respirators include N95 and KN95 masks that have markings (N95, KN95) to identify their authenticity. Respirator masks should also be disposed of when they are wet or dirty, but if they are only gently used, can be reused by letting them dry out (see more at the end of this post).  It’s important to check if the N95 or KN95 mask you are using is authentic, as many fakes are being marketed and sold in the US.  There are no authorized “children’s mask” in the N95 variety; nor do they have earloops.  

One widespread concern about using masks is their propensity to increase our intake of carbon dioxide (CO2) due to retaining exhaled CO2 in the mask.  Most medical experts say that there is no increase in retained CO2 due to masks, including this video of a respiratory therapist wearing one for 6 hours, with her oxygen and CO2 levels monitored.  However, studies such as the following have shown that elevated CO2 levels are present, and even this Mayo Clinic article mentions that CO2 levels do not increase with medical and cloth masks, but does not say the same for KN95 and N95 masks. 

  • This study of 11 individuals at rest shows that the levels of CO2 in their mask are elevated after only 15 minutes. The study evaluated KN95 masks, valved respirator masks, and powered air purifying respirator (PAPR, which assists in breathing by using positive pressure inside the mask).  The measurements taken for KN95 and valved respirator masks after 15 minutes showed CO2 levels above the threshold for short-term limits (TLV-STEL) which are set by the National Institute for Occupational Safety and Health (NIOSH).  They are much higher than the long-term limits (TLV-REL) set for 8 hours of exposure.   However, measurements using the PAPR were only slightly above the TLV-STEL.  The study concluded that hypercapnia was a real possibility for healthcare workers using masks for extended periods, but use of PAPR prevents relative hypercapnia.  

  • This study shows levels of CO2 while volunteers are at rest sitting or standing still with a mask hovers at approximately 500-700 ppm.  While using a mask, the CO2 concentration in the mask elevates on average to 2200 ppm while sitting or standing still, approx. 2500 when walking at a pace of 3km/hr with a mask, and approx. 2900 while walking at a pace of 5km/hr with a mask.  The conclusion cites that “concentrations between 1,000 ppm and 10,000 ppm can cause undesirable symptoms such as fatigue, headache and loss of concentration”, so those who are required to wear masks for long periods like students, bus drivers or cashiers may be affected.

  • Computational fluid dynamics were used in this study to show that due to the tight fit and mask composition in N95 respirator masks, CO2 levels, water vapor, and temperature are all increased inside the mask.  This leads to excessive CO2 inhalation (up to 7 times more per breath) and reduced heat transfer inside the nasal cavity (which causes the wearer to feel that they have not taken a full breath).   The authors suggested that wearers of this type of mask should limit the time the mask is worn. 

The takeaways from these studies show that it’s not advisable to wear respirator masks like the N95 unless you are in close proximity with unknown and known sources of SARS-CoV-2, and then only for shorter periods of time.  Most of us may wear well-fitting and designed cloth and procedure masks, and there are some great options for specific use out there:

  • Since it’s important that masks fit everyone well, Enro has developed their mask in 6 sizes, making it exceptionally wearable, washable and durable, with an anti-microbial coating. 

  • Seri face masks by Serionix are very soft, comfortable masks with refills that come in a choice of MERV 13 or MERV 16 filter material. 

  • Clear masks solve the problem of not being able to see half of our faces and expressions!  ClearMask seems to be the leader for medical and professional use, but many others are offering different designs with comfort and anti-fog characteristics.  MaMo Creations is a favorite among teachers and other communicators. 

  • The Vocaleasemask offers singers and performers acoustic transparency of materials for greater clarity, and a design for full range of face motion and easier breathing.  It achieves particle filtration above level 2 (the higher level) of the ASTM Standard Specification for Barrier Face Coverings (ASTM F3502-21).

  • Sunnie Face Shields are not masks, but they are popular for protection against droplets as mask requirements are relaxed.  They are very light, anti-fogging, scratch-resistant and extremely durable.  

Now, how can I wear the same mask day after day, safely? 

  • Sometimes, due to shortages, healthcare professionals must re-use their masks. Disinfecting N95 and KN95 masks with soap and water, bleach or even alcohol decreases their effectiveness.  The best way to disinfect these type masks is actually just to let them dry for 48-72 hours.  

  • If you don’t get a chance to wash your cloth face mask everyday, we also recommend letting it dry out (don’t store your mask in a plastic bag!); 

  • You can natural sprays to refresh it and remove odors, such as Cavere, which uses 70% ethanol (alcohol derived from corn or soybean), water, glycerin, peppermint oil, echinacea extract, eucalyptus oil, citric acid, and a few other ingredients.   

  • Mask sanitizing sprays such as CovaGuard use Benzalkonium Chloride (BAC), which does kill viruses but have been known to induce asthma in cleaning workers, decreased lung function in farmers, and greater immune reactions and decreased fertility in mice, among other effects.  

Masks are definitely equipment that we hope will be rendered obsolete soon, but in the meantime, we can keep on innovating with them for better comfort and efficacy.

Photo by Yoav Aziz on Unsplash

Should I Clean my HVAC Ducts?

Should I Clean my HVAC Ducts?

We all want to have clean rooms, windows, and nice fresh paint and decor.  But what about those spaces behind the walls and ceilings, like the HVAC ducts?  You would think that accumulated dust in HVAC ducts would be a major health concern.  Surprisingly….in most cases it isn’t.

There is a big discrepancy between the EPA (with whom I found knowledgeable websites such as and concur) and the NADCA (National Air Duct Cleaners Association), including all the companies they represent.  Let’s lay out the facts, people!  The EPA has posted a very informative article about whether to have your ducts cleaned, and there are only 3 scenarios where it is recommended:

  • There is substantial visible mold growth inside hard surface (e.g., sheet metal) ducts or on other components of your heating and cooling system.

  • Ducts are infested with rodents or insects.

  • Ducts are clogged with excessive amounts of debris or dust, and it’s being released into your home through the vents.

Other than these situations, chances are that the dust in your ductwork is of the normal variety and quantity, and cleaning in these cases hasn’t been proven to improve air quality.  This stands in stark contrast to advice from the NADCA, through which many companies profit by accreditation and work.  The NADCA (which on their site is now called The HVAC Inspection, Cleaning and Restoration Association) used to recommend that ducts should be cleaned every 3-5 years, and this information was disseminated via all their members (accredited duct cleaners with their own companies and websites).  Now it says that frequency of cleaning depends on homeowner considering:

  • smokers in the household

  • pets that shed high amounts of hair and dander

  • water contamination or damage to the home or HVAC system

  • residents with allergies or asthma who might benefit from a reduction in the amount of indoor air pollutants in the home’s HVAC system

  • after home renovations or remodeling

  • prior to occupancy of a new home.

If your ducts land in one of the EPA’s criteria (mold, pests, excessive debris), then your decision should lie between cleaning and replacement of the system.  If your ducts don’t have these conditions, keep reading! 

  • First of all, duct cleaning isn’t cheap!  The estimate could range between $450 to $1000 (according to the EPA).  If you encounter a “coupon” that enables you to have your system cleaned for much lower price (like $50), beware, because these companies are jokingly referred to as “blow and go”, meaning they are unaccredited and often pressure or scare homeowners into adding more expensive services once they are inside. 

  • Duct cleaning should include the entire system, not just the ductwork, because if excessive dirt is found in the ducts, the air handler and evaporator will have the same issue.  The professionals you hire should have knowledge of the entire system, and it should take two professionals three to five hours to clean the entire system of an average home. includes a checklist of items to be covered.

  • Cleaning ducts has its risks. Some areas of ductwork may require access holes to be cut, which need to be properly sealed after the cleaning. Cleaning flexible ducts carries the risk of puncture or tears, which exposes your air pathways to heavily-dusty areas like the attic.  Also, if portable suction equipment used does not have the proper filters or they are not clean, then dusty air can be released back into your home.  For this reason, it’s important to only hire professionals that have been accredited by the NADCA and follow their guidelines

  • Extra services offered, like biocides that kill mold or bacteria, and sealants that encapsulate debris to keep it in place, also have risks.  Biocides should only be applied to non-insulated areas, and be approved by the homeowner according to their tolerances and chemical sensitivity. Sealants have been shown in general not to be applied evenly over surfaces (leaving gaps) and may degrade over time, releasing more particles into the air. According to the EPA, “Most organizations concerned with duct cleaning, including EPA, NADCA, NAIMA, and the Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) do not currently recommend the routine use of sealants to encapsulate contaminants in any type of duct.”

  • There are many other sources of dust than what is coming out of your HVAC system.  Most of it is coming in from the outside on clothing, pets, and mainly air leaks in the house.  If you live by a road with high traffic or a dusty gravel road, or have one or more pets, those will have much more impact on the particles you breathe in. This study also shows that 90% of the ultrafine particles in the air of 40 houses and apartments in Germany, were from cooking, baking and toasting.  These ultrafine particles are the most concerning for health because they can penetrate deep into the lungs and even the bloodstream. 

At HypoAir, we tend to advise not “throwing the baby out with the bathwater”, meaning, let’s not go overboard in recommendations to tear out the entire HVAC system, house, etc. when you find a problem!  However if you do find mold in your system, let’s go back to recommendations on the lifespan of HVAC systems in general.  The industry recommends replacing HVAC systems every 10-15 years.  If you are in a home with a system older than that, it may be more cost effective to put money budgeted for cleaning ducts toward a totally new system–and of course, starting over with new ducts is way better than cleaning old ones.

(How to tell the age of your AC: go to the outside unit and use your phone to snap a picture of the manufacturer’s plate on the backside (side facing the wall).  If it doesn’t have a legible date, there are ways to tell from the model number. )

So, if you’ve determined your HVAC is young enough to keep for a few more years, and don’t have mold/pests/excessive debris in your ductwork, it’s best to redirect your energy and budget away from duct-cleaning, to tackle the bigger sources of dust or allergens through elimination or mitigation (often you can do 2 or 3 of these for the price of duct-cleaning!).  Here are some examples (many of our blog posts cover them):

  • Invest in a good HEPA filter and/or air purifier, at least for the area(s) of the home in which you spend the most time (portable ones can cover multiple areas)

  • Make sure that the ventilation hood over your cookstove is powerful enough to remove all the vapors released (and make sure to use it regularly!)

  • Seal up air leaks around doors, windows and outlets 

  • If you live in an area with high outdoor pollution, consider adding a heat exchanger ventilation component so that you can get fresh, filtered air through your HVAC

  • If you live in a low outdoor pollution area and like to open your windows, consider adding anti-pollen screens to some or all windows to reduce dust and pollen inside. 

  • Change your furnace filter regularly with the best one you can afford (and your system is rated for). 

  • Brush and bathe your pets regularly to reduce dust in their fur.

I hope that this article helped you to consider all the options when presented with HVAC duct-cleaning.  It certainly educated me in writing it!