Truly Natural Air Purifiers

As homeowners realize the extent of air pollution inside the home, they value making or buying air purifiers all the more.  Many purifiers require expensive manufactured filters to be purchased and changed out on a regular basis.  They can certainly do the job but our ears always perk up when something using natural materials comes along!  It’s fun to research how outdoor air is purified by plants and microbes and natural materials.   Here are some of these “new” products that use ancient natural processes.

FIrst, we’ll talk about ones you can actually buy.  

Unless you live with open windows next to a pond with a lot of green stuff on the top, you’d never experience the benefits of using algae as an air purifier.  Or, you could buy an Algae Air Purifier, which cultivates the algae in a low-maintenance tube anywhere in your home.  Algae naturally feed on pollutant particles and gasses like CO2, CO, NO2, VOC`s, PM 10 and 2.5 and transform them into oxygen, turning a problem into a solution. Their ability to absorb and remove the carbon dioxide in the air is 10 times higher than large trees as their whole bodies are photosynthetic. (Can Algae Purify Air?)  AlgenAir looks like a cool modern lava lamp, which has a light, bubbles and soothing white noise.  Algae does have a life cycle of 4-8 weeks, which at the end does not have to be dumped out on the ground.  Since it’s a natural fertilizer, the algae can be poured onto your other houseplants to be used as food.  The Aerium 3.0 comes with the container, one spirulina starter kit and sterile hydrophobic filter.  The subscription plan will reship spirulina every 30, 45 or 60 days for $24.75 for each refill.  

We wrote about the power of moss to purify air previously, but Briiv is a new product that brings it indoors.  It’s a compact filter about the size of a hot water kettle, that looks like a little terrarium on your counter.  How could this green filter possibly last for a whole year?  Yet, it does.  The company claims that it’s as powerful at 3,043 medium-size houseplants, and on its maximum fan setting it delivers 53 cubic feet per minute of purified air. This equates to a CADR of 90 cubic meters per hour.  Reviewers felt more refreshed after sleeping with the Briiv running in their closed bedroom, and enjoyed the fresh outdoor scent.  Since reindeer moss grows at high latitudes and altitudes, it is certainly an uncommon houseplant!  The price of $356 sets you up with one filter which lasts one year, and multiple filters are needed for larger spaces/more rooms.  The replacement filters (moss, coconut and nano matrix) are $38 for one set.  It’s a luxury filter that imparts the scent and look of the outdoors anywhere you place it.

“Biofiltration” could describe the way the algae and moss clean the air, and in a new adaptation,  is also the method of passing air through a thin film containing immobilized bacteria and fungi.  Researchers in Chile focused on reducing volatile organic compounds (VOCs) from building materials and paint, and polycyclic aromatic hydrocarbons (PAHs) from wood-burning.  Current air purifiers typically use activated charcoal to adsorb these pollutants, but the capacity of the charcoal will get “used up” and require disposal at some point. Instead, they found that by using the fungus Fusarium solani and the bacterium Rhodococcus erythropolis, the pollutants could be completely degraded, and the  “filter” did not degrade in performance even after eight months of continuous use. Furthermore, other microbes were captured from the air, demonstrating the potential of the prototype for retaining airborne bacteria and fungi.  (Fresh research for fresh air: Harnessing microbes for removing indoor pollutants)

It is a bit costly to use these “natural” filters in your home; we’re hoping the last one using bacteria and fungi retails for less when it’s finally commercialized!  However, by harnessing the power of 25-3000 houseplants in 1 filter, they are definitely easier than maintaining a forest of indoor plants.  I like the idea of smelling fresh outdoor scents, so I think the Briiv would be my choice.  The compostable filter elements in each device are particularly attractive, and on a replacement-filter basis really are not so expensive after all when compared to many air purifiers which cannot remove VOCs or CO2.  Bravo for the natural versions, we definitely want to see more of these!

So you’re in the market for a new car?  With or without New Car Smell?

If the idea of driving a new car is appealing, you may need to educate your nose to accept that the new car smell is not a good thing.  Thankfully, many automakers are becoming conscious of the dangers of volatile organic compounds (VOCs) that compose most new car smells, and are taking steps to reduce them.  Not a small driver for this is the new car market of China.  Over 11% of buyers in China complained about the odors they found in their new cars, according to the 2019 JD Power China Initial Quality Study. (The Self-Poisoning Car)  Apparently, Chinese prefer for their new cars to have no smell at all, which makes sense due to their genetics.  Many Asians possess a less functional acetaldehyde dehydrogenase enzyme, which is responsible for breaking this VOC down, therefore they may be especially susceptible to its allergenic effects. 

When you know about what is in the “new car smell”, you might not be too disappointed when it fades away!  Most of the smells are due to VOCs, some toxic ones at worst.   The sources are varied:

• Residual compounds from the manufacturing process and material treatment of different interior components and textiles     

• Adhesives and carrier solvents that will de-gas – as much as 2kg of adhesive can be found in a modern car, much higher than in the past where mechanical riveting and bolting was more common]

• Degradation of cabin materials over the longer term as a result of oxidation, ultra-violet light and heat. 

There are no worldwide standards for interior VOCs on new cars, but Asian countries seem to have some of the most well-defined guidelines.  Here are some of them:

Source: The Self-Poisoning Car

Testing VOCs with professional equipment can yield surprising results.  Even in a 1-year old gasoline Hyundai i10 (an economy car produced in India but not sold in the US because it was deemed too lightweight), methanol and acetone rose dramatically as the car stood in the sun for 5 hours, only reaching 68 degrees F.  After the five hour test without the engine on, the car was started, windows rolled up and AC on max with recirculation mode.  This yielded another surprise: some VOCs such as acetaldehyde rose steeply during the fourth to sixth minutes. During this phase acetaldehyde concentrations rose from an initial base of approximately 50 to 550 μg/m3, more than ten times the regulated limit in China and Japan. It was suspected that the air conditioner acted as a “sink” for some VOCs, which was flushing them out during this time.  (The Self-Poisoning Car)

VOCs in cars have even led to a new condition: Sick Car Syndrome (SCS), a phenomenon in which drivers and passengers experience short-term health problems owing to the accumulation of volatile organic compounds (VOCs) in vehicle cabins [1], [2] and is particularly prominent in new rarely used cars. The symptoms of SCS include irritation of the eyes, nose, and throat, headaches, and dizziness, among other symptoms, with potential long-term health consequences.  (Elevated volatile organic compound emissions from coated thermoplastic polyester elastomer in automotive interior parts: Importance of plastic swelling)

Some solutions from automotive material suppliers include: 

• UK company Aqdot has introduced the product Aqfresh, which is a powder composed of barrel-shaped molecules with a hollow hydrophobic cavity and polar portals, enabling them to tightly bind a wide spectrum of unwanted molecules.  Aqfresh can be applied to textiles via dry impregnation, as well as by spraying and padding during the finishing process.  It can also be incorporated via compounding or polymer masterbatch into rigid plastic parts such as dashboards and other trim pieces.  
• 3M has developed low VOC adhesive tapes and a water-based spray-on adhesive (no VOCs) that meet the Japanese Automobile Manufacturers Association (JAMA) standards for nine substances with defined limits for vehicle indoor air quality (VIAQ).  
• POM is an acronym for the chemical name polyoxymethylene. It is generally referred to as polyacetal or acetal resin.  POM has a number of applications in cars where it replaces metal such as door locks, fuel system parts, door rollers, and clips to hold trim in place.  It has properties of durability, oil and chemical resistance, and self-lubrication.  However, traditionally POM was a source of formaldehyde.  Polyplastics has developed a number of grades of POM that are low-VOC in its DURACON® POM LV Series. 

Although there are some brands that historically have higher customer ratings for interior air quality (like Honda), the last comprehensive survey of new car VOCs was in 2012, and recent reports by individual automakers regarding interior VOCs are very hard to find.  You can definitely call individual manufacturers and inquire about VOCs while shopping, but when it comes down to deciding,it’s best to see/test cars in person:  What you see in a “floor model” may not be what you get in your delivered car, either, since a 2007 study showed that interior VOC emissions varied greatly between makes, models and trims and even within the same make/model/trim.

You can do a lot to rid your car’s interior of most of its VOCs. Here are some tips to do it (How to Get Rid of That New Car Smell (Step by Step))

• Heat, ventilation, and time are certainly the main ways to offgas a vehicle. You can heat it by putting it in the sun, by running the heating system, or even with space heaters (very carefully in a small space).  When you are heating materials you are releasing the VOCs and also creating new VOCs (this study explains), so make sure when you are heating up the new vehicle you are airing it out substantially at the same time so that the gasses have somewhere to go.  Windows should be open while you are heating the vehicle. Windows can also be left open anytime it’s safe to do so.
• Deep clean the vehicle with non-toxic products:
  • You can use AFM Carpet Shampoo to deep clean carpets and upholstery; just make sure not to soak these surfaces in order to extract all the water and prevent mold growth.
  • Vacuum frequently with a HEPA vacuum.
  • Wipe down hard surfaces with disposable cleaning cloths so that you can throw them away after picking up dust, which is what many chemicals from the plastic bind to.  TotalClean is a non-toxic cleaner that’s safe for cleaning soft or hard surfaces in the car (again beware of soaking soft surfaces, however, because of the danger of mold and water rings when the material dries.)
  • Use an adsorbent like activated charcoal.  You can cut and place this filter media wherever you want in the car, and even use large pieces of it to cover seats when you’re not using them.  
  • Use an Air Angel all the time; the AHPCO cell is especially good at removing VOCs, and you can use it from your car’s power plugs while driving, or plug it into a wall receptacle via extension cord in your garage.
  • Unfortunately, flame retardants used in the foam parts may continue to off-gas for the life of the parts, so use fresh-air ventilation whenever you are driving and the outside air pollution permits you do so.

If VOCs are not reduced through the heat, ventilation and time method, you can block them using sealants. This really is the last resort, because sealing prevents further offgassing.  AFM makes a number of non-toxic products for this purpose and questions about their best application can be answered by The Green Design Center.

• Fabric seats and carpet: AFM Lock-Out is sprayed on.
• Vinyl: AFM Hard Seal is applied in thin coats using a sponge
• Other Plastic Surfaces: AFM Acrilaq is best applied with a pad applicator in 3 light coats, sanding lightly between coats. .

If you’re used to the good old-fashioned “smells” of just fresh air and sunshine, ditching the new car smell should not be hard for you…hopefully it’s the same for whoever else will be driving your new car.  A final option would be to look for a lightly used car from someone with non-toxic habits–just like the price, the VOCs should also be reduced considerably, and even if it was “professionally cleaned” by a dealership, those cleaning chemicals can be removed using the same steps above.  Goodbye, little air freshener trees, hello fresh air!

Keeping safe when using supplemental heat

When the weather turns chilly, sometimes your main heat source doesn’t heat quickly or completely, or it’s expensive to run, and you may turn to supplemental heaters for a quick way to warm up.  Supplemental heating sources like radiators, space heaters, and fireplaces are alternative options to simply turning up the heat in your home or installing a new, main heating system.  However, they have limitations and safety considerations you should note!

Portable space heaters

Sometimes the permanent heating system in your home is undersized and it can’t heat the whole home adequately.  In other cases, if you have a gas furnace, propane or natural gas can become relatively expensive!  In these cases, permanent supplemental heating (the installation of a heater in one part of the home) can help. 

Permanent Supplemental Heating

We want you to be knowledgeable about and avoid air quality poisons that are created just by heating your home with a combustion unit!  According to a Japanese study of propane, kerosene and electric space heaters used in a non-ventilated, 215 ft2 room:

• concentrations of NO2 and CO2 from all the heaters except the electric heater exceeded the 1-hr Environmental Quality Standards (NO2: 0.04-0.06 ppm) and the Building Sanitation Management Standards (BSMS, CO2: 1,000 ppm).  

• The CO concentration emitted from reflection kerosene and natural gas heaters slightly exceeded the BSMS (10 ppm). 

• The concentrations of suspended particulate matter and polynuclear aromatic hydrocarbons showed an increasing tendency during the use of kerosene-fueled heaters. 

In a study of kerosene heaters, NOx, CO2 and CO are the main gaseous pollutants emitted by kerosene space heaters. In addition, carbonyl compounds (formaldehyde, acetaldehyde, acetone) were identified, as well as ∼50 other VOCs, six of which presenting a risk for human health (1,3-butadiene, benzene, ethylene, propene, isobutene and acetylene). There is an accumulation of soot on wick heaters after a few hours of operation, which causes incomplete combustion that increases CO emissions, (CO poisonings are frequent with kerosene heater use). Therefore, the recommendation with any combustion gas heater is to ventilate profusely, or go with a vented heater model.  This article on BuildingGreen.com concurs that we should avoid unvented gas heaters. 

Sealing your Attached Garage

For many people an “attached garage” is an asset in a home: the convenience of parking and walking inside under cover is very attractive when there’s extreme weather outside!  However, from an air quality perspective, attached garages are actually a liability, unless the garage has been air-sealed from your house!

In our articles about negative air pressure here and here, we talked about how contaminants can enter your home from the garage.  The garage not only has car exhaust fumes, it can also have paint or chemical fumes from your hobby, VOCs from pesticides and insecticides stored there, and possibly even exhaust gases from your gas water heater, furnace or clothes dryer.  Need we  mention the mold and mildew spores when humidity and cardboard boxes create the perfect environment for mold?  It’s almost like having an unsanitary neighbor in the apartment next to you…now, does an attached garage still seem like an “asset” to your clean, healthy home?

If you are coming around to a healthier way of thinking about your garage, it’s essential to consider installing some boundaries with this unsanitary neighbor!  “Air sealing” is more than just a tight-closing door.  It goes from the ground (foundation), through walls and insulation and even into the attic.  That’s right–if the attic over your garage is not sealed from the attic over your home, you got it–there is shared airspace and the possibility of contaminants crossing over from the air that circulates there due to changing temperatures. 

As with most air-sealing projects, creating this boundary is easiest if it’s done during the building phase.  The easiest way is to build your attached garage as a “separate” building…as in this article.  Jake Bruton of Airow Building in Missouri does it this way: do all the framing for the house, install your air barrier, and only then, frame the garage on the other side of the air barrier.  Finally, any penetrations like electrical and ventilation must be properly sealed. 

Another way to airseal during construction is to hang drywall on the shared wall inside the garage, foam the penetrations like light switches and outlets on that wall, and also run plywood sheathing above it to the roofdeck, using sprayfoam to seal the entire barrier in the attic as in this video.  Sprayfoam really is the only way to effectively seal around ceiling joists, which often run straight over the wall from the home into the garage.     

This is all great...for new construction.  What if you are buying an existing home, or just now want to upgrade your home?  First of all, examine that shared wall from the garage side, from floor to ceiling. 

• If the drywall is finished, that’s good.  Finished drywall can be an air barrier.  However, you’ll want to remove any trim like baseboards or trim around doors, faceplates like electrical plates, and uncover any penetrations.  Get some spray foam in a can and seal all of these cracks with spray foam.   You’ll want to cover the space from the sill plate to the drywall, the spaces around electrical boxes, and around any pipes sticking through the wall like gas pipes or hot water pipes if you have a hot water heater in the garage.  Make sure to seal around the door frame if there’s dead space there. 

• If the drywall is not finished (no tape and mud or just insulation), that’s even better!  Consider removing the existing drywall on the garage side (you can install it again later if screws were used), as well as any fiberglass or rolled insulation, and sprayfoaming the entire wall.  Spray foam can be an excellent air barrier if it’s done by a pro.  Before you schedule the job, however, go to the next point and prep the attic space so that they can foam there as well.

• If the attic space between the garage and home are shared, you’ll need to build a partition wall between them.  Of course this is not a fun job, because attics are typically low, cramped and have extreme temperatures, but it’s critical if you’re going to do a thorough job.  Then, the wall can be sprayfoamed on the attic or house side, or at least foamed around the roof, rafters and joists and taped where plywood sheets come together.  

• Ventilation (air conditioning and heating) is something that should never be shared between a house and garage, because that is a sure way to pull those contaminants right in and distribute them around your home!  If you do have a shared system, consult with an HVAC company about terminating the vents to the garage and installing a dedicated mini-split.  For small garages, a window air conditioner and portable heater will do the trick!  

• If flexible ventilation ducts go over the garage with no vents, it’s really hard to get an air seal around flex ducts.  If you can’t/don’t want to switch to metal ductwork, install a collar in the attic wall that separates the garage and house (the one you build as in bullet #3 above), and attach the ends of the flex duct to it, so the wall can still be adequately airsealed.  

• The door between the house and garage, of course, is an area that needs to seal tightly.  Adjust the door so that no daylight shows around the perimeter (I know, this is easier said than done!) and use weatherstripping around the sides so that it seals when closed.  If necessary, install a “sweep” on the bottom or replace the rubber seal in the threshold so the bottom seals as well. 

Here are some product recommendations for air sealing the garage:  

• Air-sealing tapes can be expensive, but don’t scrimp: don’t use duct-tape, vapor-barrier tape or anything less than a product that is for air-sealing.  ZIP System is a great brand and be sure to buy more than you think you will need, because there always seems to be another seam to seal!  Use this tape to seal plywood edges together, seal the door frame to the drywall (if you can’t foam it), etc. 

• Spray foam cans come in lots of formulations: small cracks (less than ¼”), larger gaps and cracks ( ), pest block formula (who knows what kind of chemicals are in there), but just be sure to buy a good number of the small and large gap formulations before you start the job.  Wear gloves, safety goggles and old clothing (long hair safely tucked away) because this stuff is super sticky!  Also, if you use a can quickly, you can reuse the same straw on the next can, and save the extra straw in case one gets plugged or lost.  Unless you buy the “smart dispenser” version, the straws and remainder in the can cannot be reused after about 30-40 minutes, so be sure to have several spray areas ready when you start spraying!  After it hardens, you can use a utility knife or hacksaw blade to cut away excess foam.  Consider these different products:

• Great Stuff Window and Door gently expands so that frames will not warp under pressure.

• Great Stuff Gap and Cracks (use in gaps up to 1”)

• Loctite Tite Foam, pack of 2 for $19

• Great Stuff Pro (large cans, $14 each–a great tool for a large job because it’s easier to dispense and can be reused for up to 30 days); however it requires a special gun.  Users report that a can goes a LONG way (3-6 cans on a large home) but if you have more air-sealing to do, it’s worth having several more on hand.

• And more…

Not only will your house smell better and stay cleaner after these airsealing improvements, you’ll probably notice less cold drafts in winter and hot air in summer, since most attached garages are not conditioned.  Finally, complete your sealed garage upgrade with a funny sign reminding everyone to “close the door”...after all, airsealing can only go so far when the door is open!!

Materials to Exclude from a Healthy Home

Everyone has at least one  “young and dumb” story where they are thankful not to have had more serious consequences from doing something un-wise, to put it mildly.  One of mine is repurposing a chunk of mystery wood for bar-tops in my 1950’s home.  It had a beautiful rustic espresso color and texture; a couple nail-holes here and there, and seemed very hard.  I cut it to length outside, put several coats of clear polyurethane on it and fitted it in place.  Then the headaches began.  For several weeks I could not shake the headaches…and since I was in the middle of finishing the house, I didn’t immediately recognize the culprit.  Suddenly, the “aroma” of creosote came back to me from cutting the pieces of wood.  It’s a potent preservative used for telephone poles and railroad ties, but definitely not meant for interior residential use.  I yanked out those bar-tops and, not one to throw anything out if I could help it, added them to my landscaping in the far corner of the yard.  No more headaches: I learned that creosote is a no-tolerance VOC for me!

The point of this story is that people can become very sensitive to chemicals and VOCs, often by accident, so education is probably our best defense!  Multiple Chemical Sensitivity (MCS) is a condition for anyone that has a reaction to formaldehyde, fragrance, VOCs, etc. and can be self-diagnosed.  One in four Americans suffer when exposed to certain chemicals (25%), and half of those are medically diagnosed with MCS. (One in four Americans suffer when exposed to common chemicals)  

For those of you who are fascinated by the right way to build (and building disaster stories), a  fun podcast to watch/listen to is BS* and Beer, which BS of course stands for Building Science.  I was intrigued by the headline of what NOT to include in my home, and also because the guest speaker is Corinne Segura, author of mychemicalfreehouse.net.  Her website and facebook page are a wealth of information for building a healthy home.  Corinne survived extreme chemical sensitivities in her first tiny home and she has consulted for approximately eight years on building techniques and products, notably for many highly chemically-sensitive people.  Mold tends to underlie these sensitivities, and in Corrine’s experience with this community, MCS has strong links to depression.  Here is her list of materials to avoid:

1. Two-part spray foam tops the list. It offgasses more than expected (1-3 years), and contains flame retardants (FR).  When substitutions are made with soy and castor oil, these components do not change the offgassing.  VOCs are a major concern.
2. Vinyl sheet flooring (used frequently in mobile homes) off gases at high rates, it uses plasticizers and may contain phthalates, which continually leach out. Linoleum (which is a natural product) is not vinyl sheet flooring.
3. Rubber flooring, used for gym floors and especially made from recycled rubber tires, has high off gassing.  Many of us may know this when we get a new spare tire, if it’s stored inside the vehicle or in a trunk that’s not sealed from the cabin.  Phew!
4. Some carpet: nylon carpet has high off gas levels.  Glues used for glue-down and padding also offgas.  Flame retardants and stain-proofing, which contain PFAS, can also be included.  However good carpet is zero-VOC.  There are very good wool, polyester and a nylon brands available.
5. Some caulking and sealants: liquid asphalt and hot-mopping (for roofs), butyl caulks and sealants, and polyurethane caulks and sealants are high off gas.  The best types are made of silicone and polyether (however you will need to check warranties for the intended use area), and acrylic caulk has the next lowest offgas..
6. PFAS (per- and polyfluoroalkyl substances) are used as stain guard substances, stone sealers, floor sealers and artificial turf.  They are highly persistent in the environment and have health concerns.  If you are chemically sensitive, you’ll particularly need to consider the type of stone you want, because there is not a lot of choice in stone sealers without PFAS (particularly for white stones)!
7. Oil paints: solvent-based oil paints and primers are high VOC and slow to off-gas!  Water-based alkyd paints are a much better choice.
8. Solvent-based stains for wood: same as #7.  Unfortunately water-based stains are finicky and the contractor needs to have experience with them.  However, there are natural oil-based stains which are not as harsh (such as tung oil, which can be applied with citrus solvent).  Rubio Monocoat is a plant-based, hardwax oil wood finish that is 0% VOC, durable, matte and keeps the natural look and feel of the wood.
9. Fiberboards and particle boards are called medium density fiberboard (MDF) and high-density fiberboard (HDF), and are typically high in formaldehyde.  Alternatively, plywood is quicker to offgas. 
10. Tiles with lead: some tiles test as much as 3x higher than leaded paint!  Cutting and working with these tiles is very concerning, as cutting tile releases more dust than demolishing it. 

Corinne had more advice to offer during the Q&A session. Here are some points:

• Water-based is not always great because it may have other chemicals in it; it’s best to determine this from the MSDS or use brands that are known for non-toxicity (EarthPaint and AFM Safecoat are two that come to my mind).
• UV-cured painted surfaces are good because this process is completed in the factory and has limited off-gassing by the time it arrives in the home.
• Some people adversely react to natural VOCs like alpha-pinene, so natural materials are not always better in terms of VOCs.  You can actually reach a VOC level over CARB in a log house where everything’s made of wood!
• Canned spray foam is actually way better than 2-part spray foam because it’s 1 part, it’s thinner, way smaller amounts.  
• What makes a vinyl plank “luxury” (also called multi-layer rigid planks), besides marketing?  It has several parts to it: an SPC core (limestone-vinyl plasticizers in the core) with vinyl on top and cheap foam underlayment.  They are mainly zero-VOC and not on the “unhealthy” list. 
• Some “antique” products like pressed-wood kitchen cabinets from the 1960’s have usually finished off gassing, but 40-60 year old vinyl flooring may still leach phthalates chemicals (forever). 
• In her estimation, ventilation is way more helpful than air purifiers and Corinne would spend her money on ventilation strategies (ERV, HRV) before air purifiers.  These ventilation strategies, according to one of the hosts of the podcasts, work well even with “leaky” houses.
• Furniture foam is a different substance than 2 part spray foam.  It contains polyurethane, which has plasticizers but not flame retardants (phased out).  Only natural latex is a good substitute for polyurethane foam, but it’s not that much of a difference to chemically sensitive people because both have some off-gassing.
• Epoxy coatings are similar to the concept of 2 part spray foam if they are not mixed properly; they can offgas for some time and may have BPA.  

Corinne advises that if you are chemically sensitive, you should compile a list of your sensitivities and use a consultant who is able to specify materials for these needs, instead of just telling them “I have MCS, I need a chemical-free house”.   Since she was not currently consulting at the time of the podcast (early 2024) , she advises that Andrew Pace, Paula Baker-Laporte and Caroline Blazovsky are three that are expert consultants in this area.  She does, however, answer every question sent to her website.  Ask away and avoid, shall we say, “uninformed” mistakes!

Tight homes need ventilation, but what do I do when it’s smokey outside?

If you’re blessed to be living in a “tight” home (one that doesn’t allow much unintentional air leakage), you should know that mechanical ventilation is really helpful, if not necessary, to achieve healthy indoor air.  Humidity, CO2, particulates and VOCs can build up inside your tight home and without intentional ventilation, can lead to major mold and health problems quickly.  In this case, many people opt for an ERV or HRV so that the energy savings on their tight home don’t go “out the window” (literally!) by exhausting indoor air and pulling in outdoor air without some kind of energy exchange.   For more basic information on building tightness, ERVs and HRVs, check out our article here.

If you have an HRV or ERV and live in an area prone to wildfires, you should prepare for them by having the proper filters in place and knowing what to do with your system.  We’ve helped several clients prepare for this scenario recently, and the “smoke” was not all from wildfires!  Sometimes neighbors with bad or even innocent habits like smoking, barbequing, or sittin’-round-the-campfire can all wreak havoc on your air quality.

First of all, be familiar with your HRV/ERV unit!  This means knowing where it is, how to change its filters, and how to operate the different modes.  Hopefully the installer did a good job of allowing room for maintenance, because just like a furnace/air handler, the filters must be changed or cleaned regularly in order for the unit to work well for many years.  

Many units only come with standard MERV 8 filters, but these are not adequate to handle smoke.  Smoke presents 2 problems: particulate matter (PM10 and PM2.5) and volatile organic compounds (VOCs).  According to the US EPA, a HRV or ERV unit filter must have a Minimum Efficiency Reporting Value (MERV) of 13 to provide effective protection against particulate matter in the air we're going to breathe inside a home or office building if it's smokey outside. (How to keep wildfire smoke out of homes with mechanical ventilation systems?)  Therefore, you’ll need to know what grade filters are in your unit now, and if they are below MERV 13, inquire with the manufacturer on which filters to upgrade to. 

Before you buy new filters, however, you should consider the other part of smoke: VOCs.  You can have a MERV 16 in your unit, but it will not capture VOCs and your home will be filled with the smell of smoke if there is smoke outside!  These insidious gasses are most easily removed with activated carbon.  Therefore, a layered filter (with MERV13 or more plus activated carbon) is really the best defense against smoke.  Since not all units/manufacturers offer carbon in their filters, here are some other options to get rid of the particulates AND VOCs: 

• Check our offerings to see if we have your filter size in a MERV 13 filter plus carbon.
• If not, you can cut and layer activated carbon media behind/under your manufacturer’s MERV 13 filter.
• ((Some units use “panel” filters which are basically squares of bulk filter cut to fit the unit.  In this case you can cut your own using laminated MERV 13 and carbon media. ))

The following options are adapted from HRV with Smoke Filtration:

• Ensure there is positive pressure inside the house during wildfire events (some ERVs like Panasonic ERV can be balanced to deliver more air than is exhausted from home) so that smoke never wants to come in “illegally”.  
• Add an inline fan/filter to the intake of the ERV.  This would generate additional positive pressure without overloading the ERV fan and also filter the air before it hits the ERV.  This one has a MERV 13.
• Get a local HVAC shop to fabricate a filter box that uses a regular furnace filter with MERV 13 (or higher) and carbon, sized sufficiently to overcome any static pressure concerns, and install it in the fresh air intake before the HRV, OR you can add a media filter cabinet to the fresh air intake of your HRV/ERV and leave out the HRV/ERV filter on that side.  We can help with calculations on sizing the cabinet if you have the model of HRV/ERV available (basically it comes down to airflow/CFM). 
• Lastly, you could add one or more air purifiers or Corsi-Rosenthal cubes (CR cubes) with HEPA/carbon) to your home.  However, this is not ideal because the pollutants have already entered your home and you’re relying on these purifiers to clean your air, instead of having a “guard” filter at the entrance.

Now, here’s the part which requires discernment: in which mode to use the HRV/ERV.  

According to this article on how to keep wildfire smoke out of your home, the intake dampers of HVAC systems should be closed during wildfire incidents, and the equipment should be configured to only recirculate indoor air.  Before any smoke event occurs, you should check that the intake dampers have seals on them and they actually close tightly.  In case you think that you would run out of oxygen in a very short time in this scenario, that just isn’t the case.  Consider this calculation for 1 person staying in a completely sealed space of approximately 600 ft2; they would possibly die of carbon dioxide poisoning (at 12 days!) before low oxygen would be an issue.  Here’s where having carbon in your filters is also good, because it can also filter out some CO2 from inside your home while you close the outside vent and recirculate.  We think that a CO2 meter is a great thing to keep on hand whether or not your home is tightly sealed, and especially if you have any combustion appliances (like gas stoves, water heaters, furnaces, dryers, etc.)  

(I wouldn’t even worry about this “12 days” deadline, either, because very-tightly sealed homes are very rare!  A home in Alaska currently holds the record for being the world’s tightest home, and the owner/builder took the ingenious route of building a “box within a box” in order to air-seal and insulate it well enough for the climate.  At 600 ft2, it has a rating of 0.05 air changes per hour at 50 pascals of pressure (ACH50).  This is less than 10% of the very rigorous Passivhaus standard, which is 0.60 ACH50.)  

So, recirculating air instead of bringing in outside smokey air has a few benefits:

• It saves your filters and uses them only to filter the small amount of smoke that leaks in through unauthorized leaks (or briefly opening a door). 
• It maintains the air quality of the room above that which you would have if you were bringing in outside smokey air.
• Depending on where the intake filter is located, it could save you cleaning your HRV by not passing unfiltered smokey air through it.

This last point may not be obvious, but not all HRV/ERV manufacturers consider that wildfire smoke is a real threat to the operation of their units, because some have intake filters on the exhaust side of the heat exchanger:

Source: “How ERVs Work”

Do you see the “Fresh air from outside” on the lower left?  Imagine that this is “smoky air from outside”, passing through the fan and then through the heat exchanger, before passing through the filter on the upper right.  All those particulates just passed through a heat exchanger, and it’s likely that some of them get stuck there until they are manually cleaned out. Particles sticking to a heat exchanger reduce its efficiency and depending on their chemical makeup, may damage the surface of the heat exchanger.  Now, placing the filter on the lower left poses a maintenance issue, but it shouldn’t negatively affect the operation of the fan or heat exchanger.  This is why having a separate filter on the fresh air intake before the HRV/ERV and leaving off that top right filter inside the unit, may be the best option in wildfire areas. 

One last point: although we’re not huge fans of completely “smart” homes due to the EMF they emit, if you travel a lot or have an HRV/ERV system installed in a vacation home, it is worth practicing operating it remotely (via an app).  In real emergencies, roads can be closed quickly and if you are not able to get home right away, it becomes the difference between being able to come “home” to a clean house and one that smell like smoke (because even carbon filters will not be able to adsorb VOCs for an extended or intense event).  

Any smoke (cigarette, wildfire, campfire, barbeque, industrial or traffic accidents, etc.) is very unhealthy, so we need to do our best to keep it out of our homes, even at the cost of not ventilating for the duration of the smoke event.  The particulate matter in smoke is especially dangerous for children and people with respiratory or cardiac conditions, because fine particulates can pass from the lungs to the bloodstream. The best line of defense against particulate matter is an airtight building envelope, which by extension means closing the intake dampers of ventilation systems.  Filters with a MERV 13 rating or higher, and activated carbon if possible, should be used in HRV or ERV systems and central air conditioning units so that these units can remove any smoke that gets in.  One or more portable air cleaners with a HEPA filter and carbon are also a very good addition for use in common rooms or bedrooms at night.  It all comes down to preparation…having the filters on hand (or better yet, already installed) and knowing how your unit works is worth a lot of clean air when the smoke suddenly appears around your home! 

Marijuana smoke, just like cigarette smoke, is an air quality problem that affects a lot of people.

According to Gallup Polls, approximately 17% of Americans smoked marijuana in 2023, which is up from 12% in 2017-2021.  By inference, approximately 83% of Americans don’t directly smoke marijuana, for any number of reasons, but a good number of them deal with it as secondhand smoke (as evidenced by the number of inquiries we receive about how to protect against/remove it).  

A misguided perception: According to Beth Cohen, MD, MA,  a primary care doctor and researcher in California, her research showed that in 2017, 26% of people thought that it was safer to smoke a cannabis joint than a cigarette daily. In 2021, over 44% chose cannabis as the safer option. People were similarly more likely to rate secondhand cannabis smoke as being “completely safe” compared with tobacco smoke, even for vulnerable groups such as children and pregnant women. (Many people think cannabis smoke is harmless − a physician explains how that belief can put people at risk)  

Yet despite these increasing opinions that marijuana smoke is less dangerous than traditional cigarette smoke,  “Smoke is smoke. Both tobacco and marijuana smoke impair blood vessel function similarly. People should avoid both, and governments who are protecting people against secondhand smoke exposure should include marijuana in those rules.”  -Matthew Springer, cardiovascular researcher and Associate Professor of Medicine, University of California, San Francisco

If non-smokers are in the majority, why are they having to fight for the right not to breathe it?  We can think of several reasons:

• Conflicting studies done over the last decade have perpetuated confusion.  For example:
  • This 2012 study found that occasional and low cumulative marijuana use was not associated with adverse effects on pulmonary function, specifically air flow rate and lung capacity.  
  • In 2022, Researchers from Ottawa Hospital General in Canada compared approximately 150 lung scans from marijuana smokers, tobacco-only smokers and nonsmokers. The study found that rates of emphysema, airway inflammation and enlarged breast tissue were higher in marijuana than in tobacco smokers.  The scans showed that 75% of the marijuana smokers had emphysema. Slightly less than 70% of tobacco-only smokers had emphysema, while only 5% of nonsmokers had it. Emphysema, a form of chronic obstructive lung disease (COPD), is the third leading cause of death in the U.S. (Smoking marijuana may be more harmful to lungs than smoking cigarettes, study finds)

• Tobacco giants Altria and Reynolds American together with convenience store retailer networks have invested billions into the marijuana industry and actively support legalization.  They produce and market products that support both tobacco and marijuana, like e-cigarettes and vape pens.  (Protecting Nonsmokers from Secondhand Marijuana Smoke)
• Have societal norms flip-flopped?  Less than 20 years ago, cannabis users were advised to be “discreet”, but with widespread legalization, that’s no longer applicable.  Furthermore, you could say that those who don’t smoke are now being pressured to be discreet!.  Included in the 2008 paper “Civic Norms and Etiquettes Regarding Marijuana Use in Public Settings in New York City” is a resource from the Cannabis Action Network’s 2005 “Good Neighbor Guidelines” promoting both marijuana use and etiquettes: “Have fun with cannabis, but in your neighborhood keep a kind, discrete, polite profile. Do not consume your cannabis openly. The fewer people who know you have cannabis around, the smaller your exposure to rip-offs, overeager youths, cops, and mooches. Keep cannabis plants hidden from public view. Avoid actions that would lead to nuisance complaints like ... overly loud music or too many freaky parties.... Do not keep your stash and paraphernalia in plain view of the doors or windows. Take measures to minimize the distinct odors cannabis has when grown, smoked, or just sitting around.”

Whether it comes down to money or public opinion, we’re finding that people who do not want to inhale second-hand marijuana smoke have to fight for that right, despite some disturbing facts (Secondhand Marijuana Smoke Fact Sheet):

• Particulate levels from secondhand marijuana smoke are even higher than particulate levels from secondhand tobacco smoke. A study comparing indoor particulate matter 2.5 (PM2.5) levels from secondhand marijuana smoke and secondhand tobacco smoke concluded that “the average PM2.5 emission rate of the pre-rolled marijuana joints was found to be 3.5 times the average emission rate of Marlboro tobacco cigarettes, the most popular US cigarette brand. 
• Significant amounts of mercury, cadmium, nickel, lead, hydrogen cyanide, and chromium, as well as 3 times the amount of ammonia, are found in mainstream marijuana smoke than is in tobacco smoke.  (A comparison of mainstream and sidestream marijuana and tobacco cigarette smoke produced under two machine smoking conditions)
• One minute of exposure to marijuana SHS (secondhand smoke) substantially impairs endothelial function in rats for at least 90 minutes, considerably longer than comparable impairment by tobacco SHS. (Endothelial function is the way blood nourishes surrounding tissues via the endothelium, the single-layer cells that line our blood vessels). The findings in rats suggest that SHS can exert similar adverse cardiovascular effects regardless of whether it is from tobacco or marijuana. (One Minute of Marijuana Secondhand Smoke Exposure Substantially Impairs Vascular Endothelial Function)
• And many more…

So how do people who don’t want these health risks overcome them?

People living in multifamily buildings, whether they are apartments or condos, frequently have problems with this issue, because: the units are commonly leaky, landlords are reluctant to impose sanctions on smoking tenants who are otherwise ideal habitants, and in many states, it’s expensive and risky to bring about legal action. Therefore, it’s the burden of the non-smoker to either “prove” the harm or mitigate the problem on their own.  

In response to our own clients’ problems, we’ve done some research and want to try to help “clear the air”. 

Testing: Since marijuana smoke produces even more particulates than tobacco smoke, tenants with neighbors who smoke or vape marijuana could invest in a particulate monitor like the PurpleAir (or similar) in order to establish a history of particulates. A study used a PurpleAir monitor (PurpleAirTM Model PA-II, PurpleAir.com) alongside expensive lab equipment to show that PurpleAir is just as effective to show secondhand PM2.5 exposure to marijuana aerosol from vaping.  The benefit of using such a monitor is that data is uploaded to the internet every 2 minutes, so that a history can be established.

In addition, if the smoke is particularly heavy or your apartment is particularly leaky, test kits can be used to discover THC residue in your space (THC Surface Residue Detection Test by Mistral, $10, THC Surface Residue/Vape Oil (Pouch) Drug Test, $10)  More expensive laboratory test kits could be used if necessary: EMSL has Marijuana Smoke Contamination Test Kit that costs $95 for lab analysis upon return.  A terpenes test kit from LCS Laboratory is $200-300. The marijuana plant contains a high concentration of terpenes that are responsible for the characteristic smell of marijuana products. Terpenes are natural organic compounds that can be found in most plants, industrial solvents (as turpentine), and many cleaning supplies with the floral or citrus smell.

Cleaning: Due to the chemicals left behind by marijuana smoke, personal protective gear should be used depending on the severity of the residue::gloves, eye protectors, respirators and possibly Tyvek suits are all standard for professional cleaning crews..The best non-toxic cleaners seem to be SmokeOut and THC-Ya:

• SmokeOut Cannabis RTU Spray by EcoClear is safe for people, pets and wildlife as per the company’s policy.  It neutralizes cannabis odor on contact.  $20/32 oz. from this distributor.
• THC-Ya! By MoMar is an enzymatic cleaner compatible with hard and soft surfaces.  It encapsulates and neutralizes odors on contact while built-in detergents and beneficial bacteria destroy and remove the source of the odors. 100% biodegradable, no dyes, no solvents, and no phosphates. Non-flammable, non-corrosive, and non-toxic.

According to Restoration and Remediation Magazine, there are several other options for deodorizing and deep-cleaning soft surfaces: hydroxyl generators or ozone machines.  Their preference was hydroxyl generators.  However, both hydroxyl generators and ozone machines have drawbacks.  They may cause more harm than good by generating oxidant byproducts. In a 2021 study, hydroxyl radicals generated by a device reacted with volatile organic compounds present in the indoor space. This led to chemical reactions that quickly formed organic acids and secondary organic aerosols that can cause health problems. Secondary organic aerosols are a major component of PM2.5 (particulate matter with a diameter smaller than 2.5 mm), and exposure to PM2.5 has been associated with cardiopulmonary diseases and millions of deaths per year. (Joo et al.)

Regarding ozone machines, ozone reacts with tetrahydrocannabinol (THC) to produce at least three new oxidant products, from concentrations of ozone as low as found in the natural air.  Therefore, using an ozone generator could increase these byproducts. (Science Daily)  Another study by Berkeley Lab’s Indoor Environment Group found that ozone can remove nicotine and polycyclic aromatic hydrocarbons (PAHs) that had adsorbed onto fabrics after smoking, but that people need to wait a few hours after the generator has run and allow the space to be ventilated of new contaminants generated by the ozone, before going back inside. (thirdhandsmoke.org)

Ventilation: Although ventilation with fresh outside air does dilute contaminants,ventilation does not eliminate all the poisonous toxins and chemical components of secondhand smoke.  The Board of Directors for the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), the international standard-setting body for indoor air quality, unanimously adopted an important position statement on secondhand tobacco smoke at its summer 2005 conference.  ASHRAE Standard 62.1 reaffirms:

• There is no safe level of exposure to secondhand smoke.
• Ventilation and other air filtration technologies cannot eliminate all the health risks caused by secondhand smoke exposure.
• Tobacco smoke does not belong in indoor areas.

In 2013, the Standard was amended to state:

• Marijuana smoke should not be allowed indoors.
• Emissions from electronic smoking devices should not be allowed indoors.

The “ASHRAE Position Document on Environmental Tobacco Smoke” was again approved.  According to this position statement, “ASHRAE holds the position that the only means of avoiding health effects and eliminating indoor ETS exposure is to ban all smoking activity inside and near buildings.”  (Protecting Nonsmokers from Secondhand Marijuana Smoke)

Air purifiers: Our most effective products against these types of contaminants are the Upgraded Air Angel Mobile and Activated Carbon Filter Media; the Air Angel’s AHPCO cell and the media are most potent against VOCs.  Our Germ Defender and Whole Home Polar Ionizer (installed in central AC) work to reduce particulates by causing them to clump together and fall on surfaces, where they can be more easily cleaned.  If you have a central air conditioning unit, you can also use our Whole Home Filters with Activated Carbon to filter and deodorize, setting the fan to “on” so that it’s always filtering.  We also recommend standalone HEPA filters like Medify Air Purifiers (sized for your space).

We get you and have written on how to walk the fine line of dealing with neighbors’ health hazards.  Just like your rights to a habitable home free from mold, tenants should also have a home free from secondhand smoke.  No-smoke.org has similar good suggestions about communicating with smokers and landlords, as well as a new one: getting a note from your doctor!  You can never have too many allies in this fight for clean air, and we want to help as much as possible.

Fire and Smoke Recovery

Wildfires have been very destructive in the western half of the US in the late 2010's and early 2020’s.  As for the future, a 2022 report by the UN Environment Programme (UNEP) and GRID-Arendal projects an increase in extreme fires by 14% by 2030, 30% by the end of 2050, and 50% by 2100, due to climate change and land-use change. (breezometer.com)  

Fire disasters, like natural disasters, do not just destroy what the fire touches.  They can disrupt major infrastructures like highways and railways, power and water, and most important, air quality.  Because fires may smolder for some time, try to prepare to deal with the effects for weeks. 

If you live in an area prone to wildfires or prevailing winds that may carry smoke, here are some ways to prepare:

• Seal doors and windows with weatherstripping, caulk and door sweeps.  
• Find out how to adjust your HVAC system accordingly: you’ll want to close the fresh air intake and change over to recirculation, no matter whether you have central AC, a window air conditioner or portable air conditioner.
• Purchase extra MERV 13 or higher filters for your HVAC system, to be used on poor air quality days.
• If you live in an apartment building or condo with little control over the HVAC, consider purchasing vent filter material so you can place them in the vents into your space. Carbon vent filter material will neutralize many VOCs as well.
• Purchase a HEPA air cleaner (non-ozone producing type) and be sure to have an extra filter or two on hand.    
• Keep a number of N95 respirator masks on hand.    
• Keep canned food and bottled water on hand.
• Stock up on essentials for cleaning smoke odor: baking soda, white vinegar, rags, TotalClean

During:

• Try not to cook during a wildfire emergency, because cooking indoors increases small particulates and vapors in the air, and you won’t want to turn on your stove exhaust, as that will draw polluted outdoor air into the house.  Try to use just the canned food you have on hand.
• Monitor the filters in your HVAC system and air purifiers and change them when you start to notice a color change on the front of the filter, or when the output air starts to smell like smoke. 
• Check your local air quality and receive updates from airnow.gov . Fire and smoke maps are available under the heading fire.airnow.gov.  You can also register for a free 14-day trial of Breezometer’s Air Quality app.  Below is a diagram to understand air quality index values (airnow.gov).
• Use N95 respirators to evacuate to a safer place if necessary.  

Source: airnow.gov

After:  

• Don’t open windows and doors until the air quality index is less than 100.  When that happens, you can open windows fully to get more fresh air ventilation. 
• Set up fans near doors and windows to “push” smoke odor and soot outside.

To remove smoke odor that infiltrated from outside, or if you had a fire in your home:

• Run air purifier(s) continuously with charcoal filters. 
• Sprinkle baking soda over carpets and rugs and leave it overnight.  Then using a vacuum with HEPA filter, vacuum out the carpets.  
• Remove drapes, towels, and any hanging fabric exposed to smoke, and either launder it in your washing machine or send it for professional cleaning.  When washing it yourself, you can add a cup of distilled white vinegar to your regular laundry detergent to remove smoke.  Don’t machine dry the item until the odor has been removed; it may need an additional washing cycle.
• Wipe down all hard surfaces, including walls, ceilings, floors and windows with TotalClean or a 1:1 mixture of warm water and white vinegar (TotalClean is more gentle than vinegar and can be used on stone, wood, etc.)  Dispose of rags or wash them out with mild detergent and water as you go.  

To clean fabric-upholstered items:

• Try to remove any cushion covers that are washable.  
• Clean bare foam cushions by using “air replacement”:  Place the cushion into a large vacuum-seal bag and sprinkle baking soda over it.  Seal the bag and use your HEPA vacuum to remove the air from inside the cushion.  Let the air back into the bag to re-inflate the cushion.   Repeat several times if necessary. 
• Sprinkle baking soda over the piece and let it set overnight before vacuuming it off.
• You can also move the piece outside to air it out in the sun.  
• It’s difficult to remove smoke that’s settled into furniture, however, if it does not dissipate following using an ozone generator, you can contact a restoration company for their services if it’s a valuable piece to you.

Try an Ozone Generator to remove smoke odors:

• Ozone generators should only be used once all surfaces that can be cleaned are thoroughly cleaned (walls, floors and ceilings too!).  
• Ozone is not as effective in areas of high humidity, so running the air conditioner or a dehumidifier in the space to get the humidity down (60% or less) is advisable.  Central air conditioning and any exhaust fans must be shut down when using the ozone generator, though, because you’ll want the ozone to stay in the space. 
• Use fan(s) within the space to circulate the ozone.
• Ozone generators cannot be used in the presence of people, pets or plants, but once these are removed, they can be quite effective in removing smoke.  Follow all instructions to seal up the space and allow it to work for the full time advised before ventilating.  Contact HypoAir regarding rental of our ozone generators, or local restoration companies may rent ozone generators.    

For large areas with open walls and ceilings such as basements, garages or gutted homes, consider having them soda blasted by professionals to remove soot and smoke odor from the structure in hard-to-reach places.  Baking soda’s legendary cleaning and odor-absorption qualities can produce amazing results when combined with commercial equipment and a skilled contractor.

Don’t: 

• Spray deodorizers or fresheners to “cover up” the smell of smoke, because they do nothing to remove the contaminants, and many have toxic ingredients in them.
• Attempt to live in spaces with heavy smoke damage until they are cleaned.  “Third-hand smoke” is the term used for the way carbon and chemicals in the smoke react to the materials in your home, and it can make you very ill.
• Neglect flood remediation if the smoke damage was part of a fire in your home and fire response crews extinguished it using water.  Building materials must be removed or dried thoroughly within 48 hours in order to prevent mold growth. 

What’s in a chemical filter?

Current events certainly stimulate a lot of research, and the accidental release of toxic chemicals from storage and transportation units is no exception.  When a dangerous chemical is odorless and colorless, how can we possibly protect ourselves and the air in our homes?  Enter chemical filters, which are actually already available for purchase.

Many gas filtration media start with a base material and then add (impregnate) the base material with specialized materials.  Since all of these base materials have a multitude of miniature holes that can get “plugged up” with dust, it’s best to make sure the dust filter is clean and in place to preserve the life of the chemical filter.  The base material is incredibly light because of the vast amount of internal surface area it has in its many cavities and holes.  The way these materials  purify air is called “adsorption” (in contrast to absorption).  Adsorption and absorption both “suck up” liquids or contaminants, but there is a difference:  a sponge will absorb water, but eventually the water leaks out or evaporates.  Activated carbon, activated alumina and zeolites adsorb certain chemicals, some including water, but the adsorbed liquid or gas does not escape because a chemical bond is made, until the material is regenerated with high heat.  Since adsorption is a surface phenomenon, good adsorbents are those having large surface areas per unit mass and high attractive forces for the compounds to be adsorbed, called the solute. Although all molecules are adsorbed to a certain extent, those having high polarity are likely to be more strongly adsorbed than those having low polarity. Since water is a highly polar material, it is much more strongly adsorbed than hydrocarbons, for instance. (Air and Gas Drying with Activated Alumina)

Here are the most common base materials:

A main ingredient in these filters is activated carbon.  We’ve written about it here but when you have something more dangerous than sweaty socks or cat litter smells, we like to dig a bit deeper on its capabilities and limitations.  Activated carbon removes volatile organic compounds (VOCs) and acid gasses, which make them useful against a wide variety of pollutants.  To review, VOCs are compounds that have a high vapor pressure and low water solubility.  They are natural and human-made chemicals that are used and produced in the manufacture of paints, pharmaceuticals, and refrigerants. (EPA.gov)  An acid gas is any gaseous compound which, when dissolved in water, will form an acidic solution.  Many industrial compounds are acid gasses, but did you know that we actually exhale an acid gas?  Carbon dioxide (CO2) is an acid gas, and activated carbon is a method for removing excess CO2 in a space.  

Activated alumina is another base.  It’s a porous, solid form of aluminum oxide, otherwise known as Al2O3 or alumina. This is the same mineral that makes up the precious gems ruby and sapphire, with impurities being the source of the stones’ bright colors. After activated alumina has been evacuated of existing moisture by heating it, the high surface area and many pores of the material allow for the uptake of water and other molecules through adsorption.  (What is Activated Alumina?) At about 1.5 to 3 times the cost of activated carbon, activated alumina is pricier but very attractive for adsorbing different chemicals.

Zeolites are another base material for chemical adsorbents.  They can be naturally occurring or man-made.  Zeolite has an aluminosilicate framework. Which simply means minerals composed of aluminum, silicon, and oxygen, plus countercations. This framework provides exceptional strength and stability to the honeycomb structure. It also makes it very difficult for the positively charged atoms (cations) to leach from Zeolite. (What is Zeolite?)   Molecular sieves are a type of zeolite that are manufactured to precise frameworks and pore sizes for specific applications.

Now that you know some of the base materials, additives (also called “doping”) can enhance capture/filtration of specific contaminants.  

• Potassium Permanganate is added when sulfurous compounds may be present (such as hydrogen sulfide and sulfur dioxide).   According to this filter company, their molecular sieve impregnated with potassium permanganate oxidizes gaseous pollutants such as hydrogen sulfide, sulfur dioxide, formaldehyde, ethylene, mercaptans, and various aldehydes and alcohols.   Do you know what mercaptans are?  They are the sulfurous, rotten-egg smelling additives that are added to natural gas to help you know that there is a leak.

• Potassium Iodide:  some AustinAir filters are impregnated with potassium iodide, for increased removal of formaldehyde and ammonia.  They are best used in places like new homes, laboratories, beauty salons, funeral homes, etc. Sources of formaldehyde in homes can be carpets, wood panel, construction materials and furniture upholstery, if not an outright chemical leak. (achooallergy.com)

• Magnesium Dioxide and Copper Oxide: The air filter company Blueair adds these compounds in their activated carbon filters to remove carbon monoxide, ethylene oxide, and ozone.

So which filter is best for me?  It’s hard to plan for every scenario, but you may take into consideration the following:

• This article/table by the California Air Resource Board (CARB) in response to the Aliso Canyon gas leak (California, 2015) describes what types of filters are in a number of high-end air purifiers.  The models may have changed slightly but it can give you an idea of how air purifiers can be used to reduce specific chemicals (mercaptans were judged to be the source of most peoples’ health issues).

• If you live very close to a refinery or manufacturer of specific chemical products, you may want to find out what chemicals they manufacture, store and load, what VOCs/fumes are produced and what air filter is best to remove those VOCs. 

• If you are interested in a particular type of filter, look for (or ask for) test data that verifies it removes what it’s designed to remove.  In an MIT study of 4 consumer-grade air cleaners, only 2 of them removed the VOCs toluene and limonene effectively.  

• In the case of radon, activated carbon filters (and the others mentioned above) will not adsorb radon gas, but they will adsorb most of the radon decay products (termed “radon daughters or progeny”), which are actually the source of health issues associated with radon. (Reduction of Radon Working Level by a Room Air Cleaner).   Therefore, activated carbon is not recommended for first-line defense against radon infiltration into your home; a venting system is more appropriate and you should contact a professional if you have radon in your home.

• In the end, activated carbon is widely used for a reason: it removes a lot of VOCs!  If you don’t have a specific chemical that you’re concerned about, this type of filter is a readily available, broad spectrum weapon against many pollutants.  If your air is particularly dusty, you’ll want to make sure that it also has a HEPA pre-filter to protect the activated carbon from getting clogged with dust.

Measure it so you can improve it!

There are several great old quotes that still hold true today:

“You can’t improve what you don’t measure.” (often attributed to Peter Drucker, “father of management thinking”, Forbes.com) 

“When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.”  (Lord Kelvin, British scientist, oxfordreference.com)

Ok, so we need to measure if we really want to know what is going on.  When you’re talking about air quality, sensors are the key!  Whether you are a homeowner or a professional, an economical sensor is a valuable thing.  Here are some of the best and their many uses.

Air Flow 

There are several instruments that can be used to measure airflow.  HVAC techs use manometers or anemometers  to verify whether the installed ductwork and fans are performing as designed.  There are also many uses for these around the house!  Here are a few:

• Hold it below your kitchen exhaust vent fan to see if it is moving enough air out of the kitchen (you can do the same for the bathroom exhaust fan)
• Hold it below your return air intake when the filter is clean, and when it is dirty, to see how much a dirty filter impacts your air flow.
• Install a pollution-filtering window screen and window fan, and check the fresh airflow in and out of the room (see our post here). 

Here’s an inexpensive anemometer that not only measures wind speed, it also measures the temperature.  In order to get a volume air flow measurement in cubic feet per minute (CFM), set the output to read feet per minute and then multiply it by the square footage of the duct or window you’re measuring (width in inches x length in inches divided by 144). 

Air Pressure

We’ve written quite a bit about the “pressure” of your home; ideally it will be “balanced” so that outside air is not being pulled in through cracks and crevices (other than fresh air ventilation).  How do you really know, though, without measuring?  Air pressure sensors are called manometers and here are some other uses for them:

• Checking the pressure drop across a new higher MERV filter (we recommend MERV 13 for the best home filtration).  You can make a small hole in the filter in order to feed one of the ported tubes through, and seal it later with some tape.
• Check the negative pressure in rooms with the door closed, to see if the HVAC returns are getting proper air flow.  In this post we discuss tackling the problem of getting enough air movement with closed doors.  

Here’s an inexpensive manometer that detects pressure or differential pressure (with two ports) and has readouts in several different common units. 

CO2 

If you’ve read our post on CO2, then you know how important this pollutant can be to your wellbeing.  Too much CO2 comes from not having enough fresh air ventilation, and can be a big factor in feeling groggy, less energetic, and causing brain fog and poor mental performance.  Of course, then, you’ll want to measure it in your home and workplace, your car, and maybe even in your classroom, church or other public meeting place.  Here are some sensors that will help you do that:

• To get the most bang for your buck, AirThings 2930 WavePlus combines 6 sensors in one unit: Radon, CO2, VOC, Humidity, Temp, Pressure (Barometric pressure) for about $200.
• InkBirdPlus makes a unit that tells CO2, temperature and humidity, which are 3 key measurements for home use.  It can be hung on the wall or be portable.  This unit is about $69.

PM and VOCs

Particulate Matter (PM) is not only dust–it’s smaller than that!  Dust ranges in the 2.5-10 micron range (check out the following diagram), but when there’s smoke or cooking involved (which happen in the home all the time), particles can be less than 1 micron.  That’s where you can really see what’s going on when the toaster burns your bread!  

Source: visualcapitalist.com

Formaldehyde is a toxic VOC that is a common “off-gas” component of new furniture, flooring and pressed-wood cabinets.  It can be measured separately or as a part of Total VOCs (TVOCs).  Those who like to have their nails manicured and painted may or may not be in shock if they took a VOC meter into the salon…the same could happen in a busy restaurant with “open kitchen” concept.  Here are some sensors that you can use in the home or business (gasp!) to make sure you’re ventilating or wearing a mask when appropriate.

• This model by Temtop has a sleek design for your desk and measures PM2.5, Formaldehyde and Total VOCs ($90).
• Temtop Air Quality Monitor measures PM2.5, PM10, Formaldehyde, temperature and humidity, TVOC and AQI, with solid ratings on Amazon ($149).

Some sensors look like a sleek medical device and some look like a machine from Inspector Gadget, but remember, they will give you information your nose alone can’t tell you.  If you take out your sensor in a public place and someone asks you about it, you may be able to impart some timely wisdom that will help them, too!