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1. Diluting the Air to Reduce VOCs
The first thing you should do is to increase ventilation. You want to “turn over” the air as much as possible while keeping an eye on the temperature and humidly.
Fan In, Fan Out
The simplest way to overturn the air and ventilate (diluting the VOCs) is to put one box fan coming in and one going out – ideally on the other side of the room.
Here you need to have tolerable outdoor temperatures and acceptable humidity levels. Humidity should not be pushed over 60% for prolonged amounts of time. Both low and high humidity can damage some materials.
Positive pressure will be discussed in detail in another section, but this strategy is to move air in and out.
ERVs and HRVs overturn the air and ventilate a house. I use the Panasonic Whispercomfort ERV.
It provides 40, 20 or 10 CFM, which is a high turnover of air.
This one is not made for very cold climates. The air it brings in is halfway between the temperature outdoors and indoors, which means it’s bringing is fairly cold air most of the year in Canada. It stops working at -7 C.
When using an ERV in a small space, consider the effect on humidity as well as temperature.
Another popular one for tiny houses is the Lunos which is an HRV.
There are whole-house systems as well. Check to see if your new house has a whole house or localized ERV or HRV. You will also want to know if it has fresh air intake or dampers to let air in to make up for air that is exhausted.
A whole house air exchanger is ideal.
2. “Baking Out” a House
This section was written with Carl Grimes (HHS CIEC) of Healthy Habitats. Once you have ventilation in place you can begin the bake out. This strategy heats the house to promote faster offgassing of VOCS from building materials while moving them out.
These are general guidelines, and your results will depend on the specifics of your house including the type of offgassing.
To bake-out a house you want about 3-5 days of constant (24 hours a day) increased temperature of at least 85-90 F. You also need ventilation, at least 2-3 air exchanges each day. If you don’t ventilate, you could have reabsorption.
How to Bake Out a House (Bake out VOCs):
Step 1: Turn up the thermostat to max, use additional space heaters if needed. Get to the air to 85-90 F. You have to do a 2 day heat up at least. With 3-5 days for one full treatment.
Consult with your contractor about any materials that could be affected by high temperatures.
Step 2: Ventilate 10-20 minutes at a time to get an air exchange – one air exchange means you are replacing all the inside air with outside air, removing the VOCs outgassed so far. Do this 2-3 times a day.
You can ventilate by opening doors and windows for 10-20 minutes. If the wind is blowing, 5-10 min will do. Note: Most HVAC systems do not ventilate, most of them circulate the inside air.
Fans in windows can draw air in and out.
Watch your humidity so that you do not cause damage to materials.
Step 3: Repeat
Keep in mind, outgassing even with heat is a slow process.
Carl explains the most common reasons for this taking extra long or not working include:
• Not getting the temp elevated for long enough – it’s hard to stay out of the house for 3-5 days – so folks usually only heat only during the day so they can come back at night to sleep. That doesn’t work because it takes at least 24-36 hours to get the materials in the house warmed up.
• They don’t ventilate 2-3 times a day to remove the VOCs that have outgassed. If you don’t ventilate the house reaches a saturation equilibrium – no more can come out because the air is full – and – what has come out is reabsorbed back into the materials.
• They try to shorten the time by heating extra hot for a shorter time. This doesn’t work because it simply takes time for materials to outgas. And it takes time to get the inner materials warmed up.
If you have done this without sufficient success – especially with no improvement – then you either have a massive source of VOCs or the problem is something other than VOCs.
If you have spray foam done wrong, don’t do this. Speak to a lawyer about spray foam that is offgassing due to mistakes in installation.
NOTE: Watch the temperature and the humidity to make sure you are not damaging any materials or furniture in the house.
3. Air Filters/Air Purifiers to Reduce Offgassing
Once you have to close up again, you want to use air purifiers with high amounts of sorbent material. The charcoal and other sorbent materials absorb VOCs.
Using these while you are aggressively ventilating is pointless. Ventilation usually has a bigger impact and these can’t battle with the outdoor air, so this comes after.
Charcoal is the main sorbent material that absorbs VOCs. Check for how many pounds the unit contains. You will pay more the more charcoal it contains.
Potassium Permanganate (PP) is added to some filters to increase the removal of formaldehyde. Not all super sensitive folks tolerate PP.
EnvironKlenze uses a mineral technology which can be particularly effective for formaldehyde as well.
What about PCO Air Purifiers?
I don’t recommend PCO air purifiers (like Molekule) for high offgassing, generally. I prefer PCO for mold spores. I have a separate article about choosing the best PCO air purifier for mold.
These are the top three brands
NOTE! I have a more detailed post comparing all the brands that are best for people with chemical sensitivity. In that, I compare costs, pounds of carbon, how much air they move, how loud they are, and more.
$660 * 250 CFM * 15 lbs of Activated Carbon Impregnated with Potassium Iodide and Zeolite * True HEPA * dB 50-66 3-5ft (they are not sure) * EST early 90s
Filter replacement: HEPA/ carbon,/prefilter 3-5 years (5-year warranty filter warranty) $360
There are different filter options with different types of carbon/absorptive material. Again, reactions often attributed to Potassium permanganate. You can test out their different filter options.
Steel units, plastic on the wheels, not plastic inside.
Some with extreme MCS have picked up offgassing, but many with MCS prefer this brand.
$729.99 (often on sale for $650) * CFM 250 * dB 50 on high @6 ft
EnviroKlenz is a slightly different technology than the others here. I have been using this unit and been happy with it.
Like the others, this unit has a HEPA filter, but instead of charcoal/PP/zeolite it uses minerals including magnesium oxide, zinc oxide, and titanium dioxide to neutralize VOCs, chemical odors, and smoke.
The EnviroKlenz according to the literature, destroys most pollutants. Contrary to odor masking methods, the nanocrystalline materials contact, adsorb and then neutralize the odor-causing substances.
It is effective against aldehydes and pollutants and particularly effective against different kinds of smokes and pesticides. Activated carbon does not help that much with formaldehyde and smoke can be difficult to filter as well. My preference for this unit comes from its ability to deal with formaldehyde and smoke.
EnviroKlenz materials will chemically dismantle many VOCs. Hydrocarbons will be absorbed but not chemically modified.
The company has a number of patents and it has been tested you can see that info here (you can search and read patents here), and for a summary of research articles and references on this technology see their technical report here.
Filter replacement costs: Mineral cartridge 4-5 months 100$, HEPA every 2-3 years $150. Rated the same as true HEPA.
This air purifier has been in production for 7 years.
$1739 * CFM 300 * 12 lbs granular activated carbon & impregnated alumina (Potassium Permanganate) * True HEPA * dB 35-69 – (the company will not state how many feet this test was done at). * EST 1963
Their HealthPro is (40 to 300 CFM) (2 air changes/hr in 1125 sq. ft), dB 25 to 59
Filter replacement: Multigas cartilage 2 years $400; Post Filter 2.5 year $129; HEPA about a year (on 10 hours a day on speed 3) $109; optional Filter Pads $79
This might be one of the best-known brand names in air purifiers. Some people with MCS swear by it. But, the most severely sensitive do not always tolerate it.
The unit is made of plastic and the offgassing of the unit itself might be an issue. The potassium insert can be hard to tolerate for many (which is not a unique issue to this brand). Some people have sent back filters that smelt especially sweet or strong and received ones that were more tolerable.
Nevertheless, this is a favorite and well-trusted brand for many with MCS who want a robust top of the line air purifier.
4. Passive Absorption of VOCs
It’s not as effective as air purifiers that move a lot of air through the sorbent filter material, but you can also use sorbent materials placed around the house.
Targeting these to high impact areas like inside kitchen cabinets would be wise.
Placing carbon around the house can be quite effective to absorb offgassing including new offgassing.
Some of them come ready in little bags (pictured), which can make things easier.
Or, something in between the bags and an expensive air purifier, is to attach charcoal to a fan.
You can place carbon onto an inexpensive box fan like this – either the sheets or the pellets. The pellets will have more absorption capacity (you may need a barrier between the pellets and the fan if it blows dust).
The Holmes box fans are strong enough to pull air through a filter.
You can hang up zeolite in bags where the problem exists especially if it’s an isolated odor. Zeolite is a good absorbent material.
5. Alternative Strategies
I have heard the following anecdotal strategies from other sensitive folks who have said these have helped them to reduce offgassing. I have not tried these myself.
- Plates of onions cut in half and dispersed throughout the room.
- Plates of baking soda (another sorbent material)
- Lemon oil in a diffuser (note essential oils can add aldehydes and other VOCs, make sure this is highly tolerable for you)
6. Using Sealants to Seal in VOCs
There are some areas where using sealants could be very effective and some that are not as worthwhile.
I would seal wood products that are offgassing formaldehyde. This could include cabinets (the edges, the boxes and even the faces in some cases), shelving, laminate countertops (from underneath), MDF molding, doors and flooring.
If you need help choosing the right sealer for your specific situation, you can contact me here.
Sealants could also be used in trailers to seal in other materials like vinyl walls.
I don’t like this strategy as much for general sealing of drywall. These products tend to create an interior vapor barrier which can cause problems where AC is used. And unless you are sealing the odor of the paint, new home offgassing is mostly coming through other openings from behind the drywall.
For general sealing you might do better to create an air barrier, that might mean sealing around outlets and baseboards.
1. Sealer: AFM Safecoat HardSeal in multiple coats (2-3) can be used on the wall. Leaves a semi-gloss finish (low VOC). To paint over this you would need to lightly sand it. This is an acrylic product, the only other ingredient revealed is an alcohol.
2. AFM Safecoat Transitional Primer: low VOC, not always tolerated (1 coat) followed by Safecoat Paint or ECOS paint (2 coats). The higher gloss the paint, the more sealing properties it has. AFM Transitional Primer plus their paint has better sealing properties than most other brands of primer/paint. This is an acrylic paint.
Sealing in new drywall and insulation: AFM Safecoat New Wallboard Primecoat covered by your choice of safe paint. It’s unlikely that it is the drywall itself that is offgassing (and more likely the paint or drywall mud, the glue behind the drywall and other materials behind that cannot be sealed easily).
3. AFM Carpet Seal: This is used to seal in the offgassing in new carpet if you don’t want to (or can’t) remove it. This is a three-part system.
Shellac to Seal in Offgasing
Shellac is the best sealer for sealing in odors/VOCs.
The most well-known brand is Zinsser. The company recommends this product as its best odor-blocking primer. But not all will tolerate that. That is not what I would use.
The purest premixed shellac is Zinsser Bullseye Shellac which only lists alcohols and shellac (but does not have to disclose ingredients under 1% and I have not been able to get a clear answer on if there are any unlisted ingredients).
I used this one and was very happy with it. The alcohols need to flash off.
Their Sanding Sealer (pictured) can also be used. Sanding Sealer is dewaxed so it’s easier to paint over with a regular primer (transitional primer) and paint. To paint over the waxed you can use Annie Sloan, or a layer of dewaxed shellac first.
Make Your Own Absolutely Pure Shellac
The absolute purest shellac formula would be to make it yourself with the flakes and alcohol from www.shellac.net.
This is just the natural resin from a beetle mixed with 90% ethanol.
Both dewaxed and regular shellac (with wax) have the same ability to seal in odors.
The purest version will still show high levels of VOCs but that is from alcohol. When the alcohol evaporates those are gone, all you have is the natural resin.
Pros and Cons of Shellac
One benefit of shellac is that is works on almost every surface including plastic, metal, wood drywall, and if it’s dewaxed you can paint over it.
The downsides are that it is a very good interior vapor barrier which can cause problems with “breathable walls” when using AC. Make sure this will work for your building envelope.
Paint as a Sealant
ECOS Purifying Paint which uses zeolite as the absorptive ingredient was not very helpful in my experiments on drywall. This paint claims to use zeolite to absorb VOCs. I don’t think there is enough zeolite to do more than absorb the VOCs that are already in the paint.
To paint and seal over oil paint that is offgassing, you can get the best seal with shellac (dewaxed) then AFM Hardseal.
Painting, in general (with any brand), can help a little bit because it has a small sealing effect.
Sealing Formaldehyde Offgassing from Wood
Sealing in formaldehyde from wood products can be very impactful. Particleboards including low-density particleboard, MDF, some HDF, OSB, engineered lumber, and to a lesser extent plywood all offgas formaldehyde.
AFM Safe Seal is used to seal in formaldehyde in plywood, particleboard, and OSB.
Not recommended by the company for sealing walls, it’s only for sealing formaldehyde in wood. It’s low-VOC.
For sealing melamine particle board – only seal edges with SafeSeal.
I tested this on wood products that were offgassing formaldehyde and it works quite well.
I tried it on plywood, laminate flooring (underneath, not on top) and MDF (used as a base of a laminate countertop). Shellac outperformed it, but shellac can’t be used in every application.
Sealing in the Odor of Terpenes in Wood
Shellac on its own is good at sealing in terpenes.
Painted Look – One coat dewaxed shellac, with a top coat of any kind of acrylic/latex paint that you tolerate.
If you are not extremely sensitive to terpenes you can skip the shellac and just use paint. Use a primer like ECOS (0-VOC, generally the most popular brand) or Safecoat Transitional Primer (low VOC, not always tolerated) (1 coat), followed by safe paint (2 coats).
Pearl (or higher gloss) will give the best sealing properties. Many people sensitive to the odor of wood find that painting is sufficient.
Sealing in Fungicides in Wood
Wood windows almost always contain fungicides and should be sealed.
You can use one coat Safecoat New Wallboard Primecoat and two coats of paint is the recipe, or, shellac.
For sealing fiberglass in trailers, domes or other shelters you can use shellac. You can topcoat that with AFM Hardseal if tolerated, to add more sealing.
This is not for sealing fiberglass showers.
Sealing Vinyl Floors
Andy from Green Design Center recommends washing vinyl flooring with a degreaser that does not leave a residue. Then in one area, test to see if AFM Safecoat Hardseal adheres to it. If it does, this sealer will work well.
Shellac also adheres well to vinyl. You might want to use shellac as the primer coat. Shellac as a final coat doesn’t take water very well. But shellac is the best sealer for offgassing and plasticizers. You can put a clear coat or paint over dewaxed shellac.
ECOS Paints recommends making sure the floor is clean, dry and free of any loose dirt, grime, or waxy residue. Then lightly scuffing off any factory-applied clear protective layer with a fine sandpaper.
Then remove any sanding dust and apply three coats of ECOS Floor Paint in your desired sheen and color, allowing at least 8 hours between coats.
Some paint colors that are “poor hiding colors” will need a primer.
You can use ECOS Universal Primer first, in this case.
Sealing Laminate and Engineered Wood Flooring
Laminate flooring does not have real wood on the top. I have sealed the underside successfully with Safeseal. If you want to seal the top, Hardseal will work better. Andy Pace recommends 3 very thin coats.
Engineered wood flooring has real wood as the top layer, so you can sand or buff off the surface. Then you can apply AFM Safecoat Poly BP.
7. Making a “Safe Room” within a House
If you are still struggling to tolerate the house after using the strategies above, you will have to give it more time. In the meantime, you can create a sealed off safe room.
There are a few ways to make a safe room in a house. You can use something impermeable to seal off the walls, use positive pressure to push contaminates out, or replace all the materials in that room.
Using an Impermeable Barrier on the Wall
To create a non-toxic room in your home you can use Denny Foil, or heavy-duty aluminum foil on the walls/ceiling/floor. You can buy large sheets of foil radiant barrier at some places like Innovative Solutions.
These materials block VOCs.
Heavy-duty aluminum foil is much easier to work with than the thinner type used in cooking or the grilling foil.
You may need several layers to totally block smells, though for most people one layer will suffice.
Attaching the foil with tape
The most obvious and temporary way to attach the foil is with tape. Though tape does offgas.
You want to use green Painting Tape for this as it will not damage the walls and is easy to remove – a healthy person could rip off/take down the whole room is probably 20-30 min.
The blue tape is more toxic so I wouldn’t use that. You could use aluminum tape but it is very sticky and will leave a residue and will be hard to take off.
Aluminum tape also smells much more than green tape, though the aluminum blocks most of the smell, the smell/VOCs do come in through the edges.
Another very tolerable tape which claims 0 VOCs, but still smells a little like glue is SIGA Rissan. That is the most tolerable tape that is going to hold up, in my assessment.
Don’t underestimate the smell of the tape when you have a whole room full of it. I can tolerate any tape in small amounts sniffing it right to my nose. I am unable to tolerate any tape when there is a whole room full of it. The larger the sheets of foil the less tape you will have.
Attaching the foil with an all natural glue
I have also used the all-natural gum arabic to make a totally benign glue. As long as this can dry to the inside of the wall from the interior that will be fine to use. Do a test piece, let it dry, remove it and see how easy it is to then remove the gum arabic paste.
I would not do this where you have colder air inside than outside (AC use), though it does depend on your outside humidity and dew point. This can create condensation and mold behind the foil.
Be careful with bringing in EMFs producing devices if you use foil.
If you have central HVAC you won’t be able to isolate this room properly. You can in most instances block up one or vents but this can also cause trouble to the whole HVAC system.
Note: You can use foil on isolated areas to block offgassing. I have used this successfully on smaller areas that were offgassing like a new door.
Other materials to block offgassing
You can also use glass panels, aluminum sheets or tile.
Using Positive Pressure to Push Out VOCs
Positive pressure means you are bringing in more outdoor (or filtered) air then you are exhausting from the room. This is done with a fan (like an inline radon fan) or air purifier with an attachment for outdoor air intake.
Some people tile a room or put aluminum walls or glass up as a more permanent version of foiling walls. (Same risks with interior vapor barriers when doing this).
While this can be quite effective in pushing offgassing out of that room it comes with risks and so is not used that often.
Strategies to make positive pressure successful
If you don’t want to seal the walls with foil or another barrier you can redo one room with all safe materials.
Going as far back as redoing the walls, insulation, and floors.
As long as you have adequate isolation from the rest of the house that will usually work really well.
Keep in mind, mold VOCs (mVOCS) come through the air and cross-contaminate much easier than VOCs. This strategy is for chemical VOCs from building materials (or to keep out a neighbor’s contaminants).
This should not be attempted in a significantly moldy house. I can smell and react mold off most houses up to 100-200 ft away.
Set this up fast
Positive pressure is easiest if you have a room within a room.
I have created the smaller room with sheets of rigid foam. But polyethylene plastic, house wrap, foil, a glass greenhouse or any other air barrier can be used.
Having a room within a room simplifies problems you could cause by creating an interior vapor barrier (humidity, condensation in walls) as well as pushing air into walls with positive pressure.
You want the room to be big enough to be able to put in a dehumidifier if needed and a heater.
Positive pressure without a barrier on the wall
Some people have used positive pressure in a room (with no barrier) which is the riskiest way to do it.
This could push moisture into the wall and I would consult with an architect or building science expert before using that in your house.
Double room for extreme containment
If you need to go to extremes to control for cross-contamination you need an entrance room as well. Use zipper doors to create a vestibule.
When using a double room system, pressurize the main room at 2 pascals for pressure – as recommended by Carl Grimes.
When using the entrance room, pressurize that with the air from the main room to control contamination from the main house.
The air that you are bringing in needs to be clean.
How to bring in the air
You may choose a simple in window fan system, an inline radon fan, an ERV/HRV with bias, or the IQAir intake kit to bring in air, depending on your needs.
8. Should you Use Ozone?
Though some folks have successfully used ozone to help reduce offgassing, this is the riskiest strategy so it’s last on the list.
Ozone can work for smoke, fragrance and mold. But with new homes VOCs, it doesn’t act as predictable. Plus it leaves behind terrible oxidization odors in many materials.
It’s also dangerous to work with and can do damage to materials in large doses.
I have used this successfully to offgas an all metal trailer. But I would not use this to break down VOCs in a new house, personally.
See my post on ozone for more details and safety precautions.
Corinne Segura is a Building Biologist with 6 years of experience helping others create healthy homes.
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Carl Grimes, Certified Indoor Environmental Consultant, wrote the section on baking out a house and consulted on the section on using positive pressure to create a safe room.
Luke Skaff, Electrical Engineer, consulted on the section on air purifiers.