Mitigating, Sealing, Remediating Offgassing (VOCs, Fragrance, Smoke)

This article will cover ways to reduce offgassing including new paint, formaldehyde as well as other residual smells in a house like fragrance and smoke.

get rid of smoke smell, residual cleaning products, fragrance, reduce offgassing

I recommend all of the products here, some products have affiliate programs and some do not. Upon purchase, I earn a small commission though affiliate links at no extra cost to you.

If you need assistance choosing the best air filter or strategy for remediating offgassing or fragrance for your home, please contact me for a one-on-one consultation.

Table of Contents:

1. Diluting the Air to Reduce VOCs
2. Air Filter/Air Purifiers
3. Absorbing VOCs
4. "Baking out" a House
5. Cleaning Surfaces of Residues
6. Sealing Surfaces/ Sealing in VOCs and Odours
7. Making a Safe Room Including Foiling, Renovating and Using Positive Pressure
8. Ozonating for Fragrance and Smoke

1. Diluting the Air to Reduce VOCs

Fan In, Fan Out
The simplest way to overturn the air and ventilate (diluting the VOCs) is to put one box fan coming in a one going out - ideally on the other side of the room. You can also get these at Walmart for a good price. Here you need to have tolerable outdoor temperatures and acceptable humidity levels. Take some caution here if you don't have the same amount of air going in and out with what the effects of the negative or positive pressure will be. You will need to watch humidity in some climates, humidity should be below 55% humidity in hot weather.

ERVs and HRVs overturn the air and ventilate a house or trailer. I use the Panasonic Whispercomfort ERV in a single room trailer. It provides 40, 20 or 10 CFM, which is a high turn over of air. This one is not made for cold climates. The air it brings in is halfway between the temperature outdoor and indoor, 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.

2. Air Filter/Air Purifiers to Reduce Offgassing

The Best Air Filters for the Chemically Sensitive - What to Look for:
  • Sorbent Material - How many lbs, type of material, tolerability of material, does it have potassium permanganate (which is harder to tolerate but provides better absorption of many VOCs), do they have test kits
  • HEPA - At least true HEPA: 99.97% of particles done to 0.3 microns
  • CFM - CFM to tell you the air exchanges/hour, you want a least 1 ACH, ideally 5
  • Offgassing -Plastic or glue in the unit? Glue in the filters? Motors "burned in" or encased/sealed?
  • Other Comparisons - How loud they are (dB), the cost of replacing filters, and year established (so you can feel certain they will be around to replace filters and parts).
What are Air Exchanges per hour (ACH) - Air exchange per hour is how many times you are "replacing" the air in the room per hour, this is a key area of comparison with air purifiers. ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) recommends a minimum of 4 ACH for patient rooms in hospitals, 5 for intensive care units and 25 for operating rooms. 

For the purposes of those extremely sensitive to mould and VOCs, we want about 5-10 air exchanges per hour. To maximise how much air in the room the air purifier can process, put it in a central location.

How do you Calculate the ACH from a Unit Specs - You always want to find the CFM of the unit. The CFM is the capacity of the unit to move air - how much air it moves through the machine. CFM stands for Cubic Feet Per Minute. You need the CFM to calculate ACH. I have two calculators here to properly size these units. 

If you are interested in PCO technology that is more geared towards filtering mould, see my article on air purifiers that use that technology. This article is about the classic types.

A Comparison of Brands of Air Purifiers for MCS:

AirMedic Pro 5 Ultra
$1400  * 28-30 lbs carbon * "Super HEPA" * 400 CFM * dB 50-75 @1ft * EST 1994

Filter replacement: Carbon Filter 2-5 years $172; Super HEPA 2 years $131;
Pre-filter 3 months $132

Some of the most extremely sensitive folks prefer this brand but not all have tolerated it. All metal. Filters don't offgas. No glue on the HEPA like true HEPA has. Option to have true HEPA which has glue.

AirMedic Pro 5 HD MCS is made for MCS -  The burn in motor by running and offgassing it for 6-8 hours. You can choose the carbon blend from an option of 7 blends in a test kit. It has 24lbs carbon and is dB 35-60 @1ft.

You can buy some models at Walmart or through some sellers on Amazon.

Healthmate Plus
$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.

You can buy them at Green Design CenterWalmart and Amazon. They also sell the replacement filters at Walmart.

enviroklenz air purifier for MCS offgassing VOCs smoke

$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 nuetralise 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.

EL foust air purifier filter for offgassing MCS VOCs formaldehyde
E.L. Foust
400 Series Air Purifier
$796.60 * CFM 380 * 60% Coconut shell carbon / 40% potassium permanganate (Standard Mix) 8 lbs * not true HEPA, 99.97  * dB 22-24 @3ft * EST 1974

Filter replacement: HEPA which can last up to 2-3 years $112. Pre-filter 2-3 months $13. Carbon media tray 6-9 months, up to a year $75

They have a sealed motor - bearings are sealed in. They run the motors outside for 2-3 days first to offgas them.

Metal construction, uses no adhesives, have HEPA filters without any glue. These are made for the chemically sensitive and some of the most extremely sensitive like this brand. They sell filter sample kits so that you can check out the different materials used. Generally, for the extremely sensitive, PP is difficult to tolerate. The most sensitive should start with their pure Bituminous coal filters. Having a sealed motor will be key for the most sensitive though this one has a lot less carbon than the other models.

$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 HealhPro 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. 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 unique 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.

You can buy the Healpro and Multigas directly through the IQAir website.

amaircare air purifier filter for VOCs MCS offgassing
Amaircare 3000
$700 * 225 CFM (in 1688 sq ft 1 ACH) * Claims no offgassing * Depending on the option you choose it contains up to 30 lbs of carbon * True HEPA * dB 43 to 61 @ 6 ft * EST 1994 * Made in Canada

Filter replacement: Prefilters + VOC media/year (12 lbs) $119; HEPA Filter 2-5 years $200

Made of metal, no plastic or foam. The HEPA is rated at 2-5 years when the prefilter is maintained. One person with moderate MCS said the HEPA filters smelled like chemicals. He requested a new one which was better.

You can find this model at Walmart or through some sellers on Amazon.

airpura air purifier filter for MCS offgassing VOCS
Airpura C600-DLX
$900 * 440 CFM  (2 air exchanges an hour 2000 sq. ft. with) * 26 lb Coconut Shell Carbon * dB 28.1 - 62.3 @6ft. * EST 2004

Filter replacement: Carbon filter 2-3 years $350; Post filter 1 year $100; Pre filter 6-12 months $40; HEPA (not true HEPA) 1-2 years $60

Claim All metal housing, ensures no plastic vapors are emitted.

Didn't work for some people with MCS although some do well with it.

They sell these at Walmart.

3. Absorbing VOCs

Placing carbon around the house can be quite effective to absorb offgassing including new paint fumes. You will need large amounts like these from Walmart or Amazon.

You could also place carbon onto an inexpensive box fan like thisthe sheets or the pellets. The pellets will have more absorption capacity (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.

I have heard the following anecdotal strategies from other sensitive folks but have not tried these myself:
  • Plates of onions cut in half and dispersed throughout the room.
  • Plates of baking soda
  • Lemon oil in a diffuser (note essential oils can add aldehydes and other VOCs, make sure this is highly tolerable for you)
Paints that claim to absorb VOCs don't make a significant dent. I do not recommend those except for decoration and for a very subtle improvement. ECOS has a paint that contains zeolite. Some have reported this has helped but others have reported that it hasn't.  I don't think adding a little bit of zeolite to paint will make a difference. However painting in general can help a little bit.

It would be more effective to hang up zeolite in netting bags where the problem exists especially if it's an isolated fragrance.

4. "Baking Out" a House

From Carl Grimes HHS CIEC of Healthy Habitats. Note 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.

how to bake out a house to bring down offgassing and reduce VOCs

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.

Step 2: Ventilate 10-20 minutes at a time to get an air exchange - an 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: The HVAC does not ventilate, it just circulates the inside air. Fans in windows can draw air in and out.

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 - its 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. 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 (cleaning products, personal care products, or materials with semi-VOCs) -or- the problem is something other than VOCs.

5. Cleaning Surfaces of Residues

How to to remove cleaning product and fragrance residue from walls, floors, furniture:

1. Baking soda and water or vinegar.

2. Baking soda and hydrogen peroxide can be a powerful cleaner (and bleaching agent). Some people add a little bit of Seventh Generation dish soap to this mixture to wash down the walls, dry them, and repeat.

3. Wiping down walls with alcohol (vodka can work).

4. Enzyme cleaners that can break down odours. Biokleen is a good cleaner to remove toxic cleaners. Another enzyme cleaner, Earthworm Spray works well at breaking down organic smells. Liquid-Ate is another one I have used (better priced in Canada). I also used the Nature's Miracle old formula. The new formula has a lot of complaints in reviews.

5. TSP can also be used to get rid of fragrance residues - but this is not exactly non-toxic and you need to take caution here. It will damage many surfaces so it's only for certain applications and you must research how to use it safely.

6. Washing walls and floors with orange oil soap solution can remove toxic fragrance.

6. Sealing Surfaces / Sealing in Offgassing and Odours

Paints & Sealers

For Walls and New Paint

When you have walls with new paint that is offgassing or that have soaked up other problematic smells, you may want to seal them.

If you can, you can try and sand off the paint first, or you can go ahead with sealing them.

Here are some approaches:

1. Sealer: Safecoat Hard Seal in multiple coats (2-3). Leaves a semi-gloss finish (low VOC). (To paint over this you would need to lightly sand it). Shellac is another sealer that can be used, discussed in detail below.

2. Safecoat Transitional Primer (low VOC, not always tolerated) (1 coat) followed by Safecoat paint (2 coats). Safecoat Pearl luster will give the best sealing properties. If you cannot tolerate this brand you can use another brand of primer and paint. Primer and paint is the least successful sealing option as it will only help slightly.

AFM products do not seal in perfume or cat urine. They are for pourous surfaces only. Some people have said they seal in essential oils smell residue but the company does not make claims it will work for that application.

Sealing in new drywall and insulation: Safecoat New Wallboard Primecoat covered by Safecoat paint is recommended by AFM.

Sealing in Fragrance, Smoke, and Offgasing

Shellac is the best sealer for sealing in odours/VOCS. The most well-known type is BIN. Zinsser the company, recommends this product as their best odor blocking primer. But the purest premixed shellac is the Universal Sanding Sealer 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). The absolute purest one is to make it yourself with the flakes and alcohol from

Both dewaxed and regular shellac (with wax) have the same ability to seal in odours. Why Zinnzer recommends the more toxic BIN Shellac Base Primer over the barebones Sanding Sealer, wasn't clear to me, and the rep I talked to did not seem to know much about this other than reading out what they are marketed as.

shellac from
One benefit of shellac is that is works on almost every surface including glass, metal, ceramic, and if it's dewaxed you can paint over it. The downsides are that it is a very good interior vapour barrier which can cause problems with "breathable walls" when using AC. Make sure this will work for your building envelope.

It is hard to "read" the VOCs levels in these products - the white ones and the synthetic might not be well tolerated. The purest one still shows high levels of VOCs but that is from alcohol. When the alcohol dries those are gone, all you have is the natural resin.

ECOS has a purifying paint. Zeolite is the absorptive ingredient in there which will absorb a little bit of VOC odour.

Clients have reported it did not work on sealing tung oil. I have only heard from one person that had success with using this to seal in fragrance.

To paint and seal over oil paint, you can get the best seal with shellac then AFM Hardseal.

For Sealing Wood


AFM Safe Seal normally is for sealing in offgassing materials  - usually for sealing in formaldehyde in plywood, particle board and OSB- not recommended by AFM for walls. It's low VOC.

For sealing melamine particle board - only seal edges with Safeseal

Sealing in terpenes

Clear Look - Shellac or if you can tolerate AFM products, you can try a topcoat of Safecoat Acriglaze, Hard Seal or Acrylacq. Shellac itself is good at sealing in terpenes.

Painted Look - One coat dewaxed Shellac - top coat any kind of acrylic or latex paint that you tolerate.

For shellac you make yourself, check out mix and the instructions there, they recommend how many lbs of shellac is needed with 90% ethanol.

If you just want to use paint over the wood, Safecoat Transitional Primer (low VOC, not always tolerated) (1 coat) followed by paint (2 coats).  Pearl will give the best sealing properties. This will help with terpenes. Though AFM is not the best-tolerated paint in my experience with clients.

Seal in fungicides

One coat Safecoat New Wallboard Primecoat and two coats of paint is the recipe. Or shellac.


To seal fiberglass - use shellac, and you can top coat that with AFM Hardseal if tolerated, to seal in the shellac or to add more sealing.

7. Making a Safe Room within a House

There are a few ways to make a safe room in a house.

Foiling a room

To create a non-toxic room in your home you can use Denny Foil, or heavy duty aluminum foil on the walls/ceiling/floor. These materials block VOCs (chemicals/toxins including mould). 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.

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 (small room). 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. You can buy large sheets of foil radiant barrier at some places like Innovative Solutions.

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.

I have used this successfully on areas that were offgassing (a new door).

The only thing in the room should be clean bedding i.e. a new non-toxic mattress or camping cot (etc). New non-toxic bedding and pillow. Be careful with bringing in EMFs producing devices if you use foil. Practice decontamination and isolation - i.e. by new clothing for the bedroom and shower before entering. This will be a safe clean non-toxic place to sleep. It should help insomnia immediately. But be careful that when you open the window or the door that the air coming in might not be good, so this won't be a long-term solution.

If you have central HVAC you won't be able to isolate this room properly. You can in some instances block up vents but this can also cause trouble to the whole HVAC system.

Positive Pressure

You can do this with or without a vapour barrier, with just positive pressure, there are some instructions and discussion here and here.

Some people tile a room or put aluminum walls or glass up as a more permanent version of foiling walls. (Same risks with interior vapour barriers when doing this).

IQ Air intake system
Another option is to redo one room with all non-toxic products including 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 might work for you. Keep in mind, mould tracks in and cross contaminate much easier than VOCs. This should not be attempted in a significantly mouldy house. I can smell mould off most houses up to 100-200 ft away.

Positive pressure is easiest if you have a room within a room. I have done this with sheets of rigid foam. But polyethylene plastic, house wrap, foil or any other air barrier can be used. Having a room within a room simplifies problems you could cause by creating an interior vapour 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.

Some people have used positive pressure just in a room (with no barrier) which is the most risky way to do it.

To control for cross-contamination you need an entrance room as well. Use zipper doors. You may need to decontaminate in this room. (The other option is to have this open right up to an exterior door. A outdoor shower could be made in that case). 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 main house. The air that you are bringing in needs to be clean - if the house is significantly mouldy you can not bring in air from right outside for this to work.

You may choose a simple fan system or an ERV/HRV biases, or the IQAir intake kit to bring in air, depending on your needs.

8. Using Ozone for Fragrance and Smoke 

Most people don't recommend ozone because it's high risk. It's high risk in terms of the safe use of it if you don't know all the precautions, and it's high risk because of possible byproducts.

There are a few things I would still use ozone for. I have had a lot of success using high dose ozone on all metal trailers to bring down glue offgassing. I will use it to shock treat mould in certain cases.

It is often used successfully on fragrance and smoke odours, not in shock treatment doses, in lower doses. Lower doses are less risky. It is not usually successful with typical offgassing from building materials - I would not use it for that purpose.

For fragrance and smoke start with low doses for short amounts of time and stop if you are just starting to produce byproducts. Read my full post on ozone for precautions and airing out.

You don't need a super powerful ozone machine for lower doses and shorter times, a simple one like this will do.

See my post on ozone for more details and safety precautions.

You can use ozone more safely on objects and some furniture as long as you know what it negatively reacts with (and know what it can degrade), or are willing to experiment.

Corinne Segura is a Building Biologist with 5 years of experience helping others create healthy homes.

Buy Me a Coffee at ko-fi.comDid you find this post helpful? If so you can buy me a coffee to support the research behind this blog. Thank you!

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. 


Anonymous said...

I purchased an EnviroKlenz air purifier and have been running it in the garage for 2 days to out gas. I think it is the machine motor area. It looks like the thing that spins is some sort of plastic. Do they usually have to out gas for long? It hasn't gotten much better running for 2 days.

Corinne Segura said...

Definitely depends on the person. I noticed the mineral odour as the main odour there. I'm not sure sensitive to motors anymore.

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