That new house smell is a mix of volatile organic compounds (VOCs) coming from the building materials.
Strategies to mitigate and reduce the VOC levels range from diluting the air, absorbing the VOCs, speeding up the offgassing, sealing in the offgassing, and lastly chemical breakdown of VOCs.
Of course, you will need different strategies for different situations and for different materials that are offgassing. Only some materials can be sealed up, for example.
This article ranks the strategies from what I would start with to the last thing I would consider.
If you’re extremely sensitive to VOCs you might also want to see the article with more extreme strategies to create a “safe room” within a house.
I recommend all of the products here, some products have affiliate programs and some do not. Upon purchase, I earn a small commission through affiliate links at no extra cost to you.
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 humidity.
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.
You can get these on Amazon.
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 so check the warranties on your wood floors among other items.
Positive pressure will be discussed in detail in another section, but this strategy is to move air in and out.
ERVs (energy recovery ventilators) and HRVs (heat recovery ventilators) overturn the air and ventilate a house with balanced air.
I use the Panasonic Whispercomfort ERV which provides 40, 20, or 10 CFM (cubic feet per minute), which is a high turnover of air.
(If you want to see how to mount this in a window instead of installing it in the ceiling see this article).
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 in 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 small spaces 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 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 SPF 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.
$885 * 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 iodide. 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.
$699 * CFM 250 * dB 50 on high @6 ft
EnviroKlenz is a slightly different technology than the others here. I have been using this unit and have been happy with it.
Like the others, this unit has a HEPA filter, but instead of charcoal/zeolite it uses minerals including magnesium oxide, zinc oxide, and titanium dioxide to neutralize VOCs, chemical odors, and smoke.
The EnviroKlenz according to the literature, destroys most pollutants. Contrary to odor masking methods, the nanocrystalline materials contact, adsorb, and then neutralize the odor-causing substances.
It is effective against aldehydes and pollutants and particularly effective against different kinds of smoke and pesticides. Activated carbon does not help that much with formaldehyde and smoke can be difficult to filter as well. My preference for this unit comes from its ability to deal with formaldehyde and smoke.
EnviroKlenz materials will chemically dismantle many VOCs. Hydrocarbons will be absorbed but not chemically modified.
The company has a number of patents and it has been tested you can see that info here (you can search and read patents here) and for a summary of research articles and references on this technology, you can ask to see their technical report.
Filter replacement costs: Mineral cartridge 4-5 months 100$, HEPA every 2-3 years $150. Rated the same as true HEPA.
This air purifier has been in production for 7 years.
$1299 * CFM 300 * 12 lbs granular activated Carbon & Alumina impregnated with 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 years $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.
You will need large amounts like these from Amazon.
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 also use activated carbon fabric to cover areas that are offgassing.
You can hang up zeolite in bags or zeolite in pucks 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.
- Onions chopped up and placed throughout the room (more info on how that works here)
- Plates of baking soda (another sorbent material)
- Lemon oil in a diffuser (note essential oils add aldehydes and other VOCs but can kill bacteria and mold and can break down plug-in air freshener (the how-to for that is here). How to use it safely is covered here)
6. Using Sealants to Seal in VOCs
There are some areas of a house 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 in extreme cases, flooring.
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 itself, new home offgassing is mostly coming through other openings from behind the drywall.
For general sealing of what is behind your walls, it’s better to create an air barrier by sealing around outlets and baseboards.
Hardseal is a product made by AFM to block offgassing. Use it in multiple coats (2-3) can be used on the wall. Leaves a semi-gloss finish and is low VOC. To paint over this you would need to lightly sand it. This is an acrylic product.
2. AFM PolyBP
This is a polyurethane, not originally formulated to block offgassing, but if that works on your substrate it is the best AFM sealer for blocking VOCs.
This low VOC primer can be used to seal in offgassing by using 1 coat followed by Safecoat Paint or ECOS paint (in 2 coats). AFM Transitional Primer plus their paint has better sealing properties than most other brands of primer/paint and it’s often used to seal in offgassing or fragrance on walls. This is an acrylic paint.
Safe Seal is used to seal in formaldehyde in plywood, particleboard, and OSB. Sealing in formaldehyde from wood products can be very impactful. Engineered woods including particleboard, MDF, HDF, OSB, engineered lumber, and to a lesser extent plywood all offgas formaldehyde (or isocyanates).
Not recommended by the company for sealing walls, it’s almost exclusively for sealing formaldehyde in engineered wood. It’s low-VOC. For sealing melamine particle board (laminate) – 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) and it worked. You can paint over this.
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).
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.
However, please see my whole article on how to offgas new carpet which goes through what I would do step by step.
In my tests, shellac was the best sealer for sealing in odors/VOCs. Though some people report the odor returning.
The most well-known brand is Zinsser. The company recommends BIN Shellac as its best odor-blocking primer. But not all will tolerate that. That is not what I would use in most cases.
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 you can paint over it with a transitional primer and paint. To paint over the waxed Bullseye Shellac you can use Annie Sloan Chalk Paint, 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. 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 it 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.
7. Paint as a Sealant
ECOS Purifying Paint which uses zeolite as the absorptive ingredient was not very helpful in my experiments on drywall but I have heard from readers that this was very helpful in stopping fragrance from coming through. This paint uses zeolite to absorb VOCs.
To paint and seal over oil paint that is offgassing, you can get the best seal with shellac (dewaxed) and then AFM Hardseal.
Painting, in general (with any brand), can help a little bit because it has a small sealing effect.
Sealing by substrate:
1. Sealing in the Odor of Terpenes in Wood
Shellac on its own is good at sealing in terpenes.
Painted Look – One coat dewaxed shellac (then sand slightly), then AFM Transitional Primer, then any 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.
2. 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.
3. Sealing Fiberglass
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.
4. 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. Shellac is the best sealer for blocking offgassing and plasticizers. You can put a clear coat or paint over dewaxed shellac with some special primers.
ECOS Paints recommends making sure the floor is clean, dry, and free of any loose dirt, grime, or waxy residue. Then lightly scuff 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.
5. 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. 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 and I would not use this.
Ozone can work for smoke, fragrance, and mold. But with new homes VOCs, it doesn’t act as predictably. 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.
If you’re extremely sensitive to VOCs you might also want to see the article with more extreme strategies to create a “safe room” within a house.
Corinne Segura is a Building Biologist with 8 years of experience helping others create healthy homes.
Did 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.