How long does it take plywood to off gas?

For most people, exterior plywood in a build will be sufficiently offgassed by the time the building is complete. If you are extremely sensitive you should test out plywood when new, after a few weeks and after 2-3 months of airing. You should also compare that to OSB, to see which is better for your health.

mychemicalfreehouse.net - Chemical Offgassing from Pressed & Laminated Wood Products

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A Guide to Choosing Pressed, Engineered and Laminated Wood Products and their Formaldehyde and VOC Levels This post will cover pressed wood and laminated wood (engineered wood) products used in construction and in household items like furniture and doors. We will look at which adhesives are used and what chemicals they offgas. Formaldehyde levels will be noted, as they vary between engineered wood types. But not all engineer wood is pressed together with formaldehyde.

I will also note which wood species are commonly used.

This post contains affiliate links to relevant products that I use and recommend. Upon purchase, I earn a small commission at no extra cost to you. Methylene diphenyl diisocyanate (MDI) – offgasses methylene diphenyl diisocyanate, though the companies claim this cures into a polyurethane. Phenol-Formaldehyde (PH) – The change to CARB 2 regulations forced most furniture/cabinet companies to move to phenol-formaldehyde. The offgassing is much lower and in many products comes to a complete cure in a short amount of time. Urea-Formaldehyde (UF) – This is the type of formaldehyde that offgasses at higher levels and for longer. When you think of furniture or flooring that is offgassing for many years it was likely made of urea-formaldehyde. Try and avoid this type.

No added Urea Formaldehyde (NAUF), this almost always means PF is used.

No Added Formaldehyde (NAF), this means no formaldehyde is added to the product. They cannot be labeled “formaldehyde-free” because wood naturally contains formaldehyde. No added formaldehyde products are often made with MDI or “soy-based” glue. Soy-Based Glue – Soy-based glue is not just one formulation. They use soy protein mixed with polyamidoamine-epichlorohydrin (PAE), isocyanates and aldehydes. (From the co-inventor of the adhesive for Purebond Plywood). This one is called soy-PAE. A similar type of soy-based glue that may be used to replace formaldehyde in MDF and particleboard is a amine-epichlorohydrin adductt/soy protein/isocyanate (source).

Product Certification Levels for Formaldehyde

CARB II – Formaldehyde Levels

CARB II is a standard set by California for products sold there, but almost all building products across North America comply with this requirement. Products that fall under this standard include hardwood plywood, medium-density fiberboard, and particleboard – these are pressed wood products sold for interior use. It does not include exterior sheathing products like exterior plywood (softwood plywood) and OSB.

(The allowable limits for TSCA Title VI are the same as CARB).

CARB II Formaldehyde Limits Are:

Hardwood Plywood 0.05 ppm (parts per million) Medium-Density Fiberboard (MDF) 0.11 ppm Thin MDF 0.13 ppm Particleboard 0.09 ppm

E-0 E-1 and E-2 European Formaldehyde Levels

E-1 certifies that boards release less than 0.1 ppm (parts per million) of formaldehyde; for E-2 boards 0.1 ppm and 0.3 ppm; and E-0 is 0.07 ppm.

GreenGuard and GreenGuard Gold Formaldehyde Levels

GreenGuard allows 0.05 ppm (parts per million) formaldehyde and GreenGuard Gold allows 0.0073 ppm formaldehyde.

How Much Formaldehyde is Acceptable for Those Avoiding Toxins?

How do you interpret these levels?

Formaldehyde is naturally occurring in wood, plants, animals (including humans), and therefore in the outside air as well. In fact, wood has a level of natural formaldehyde high enough that if you made a house completely out of wood, you could go over some recommended indoor formaldehyde levels. Formaldehyde is also produced by human industries, adding to the natural levels in outdoor air everywhere.

Formaldehyde Reference Levels

Level Reference 0.0002-0.006 ppm Rural and suburban outdoor air (source) 0.0015-0.047 ppm Urban outdoor air (source) 0.0073 ppm GreenGuard Gold levels for products in a room 0.020-4 ppm Average levels in conventional homes/indoor air (source) 0.04 ppm Canada long-term exposure 8-hour average exposure limit 0.05 ppm GreenGuard levels for products; CARB target level within a home 0.08 WHO guidelines for exposure 0.10 ppm Upper limit for residences ASHRAE, EPA, short term exposure limit

Level at which individuals have reported symptoms in studies

Health Canada short-term exposure 1-hour average limit 0.50 ppm OSHA 8-hour time-weighted average (TWA) action level workplace limit 0.80 ppm Level at which most people first detect odor 56 ppm PAC-3 (Protective Action Criteria), AEGL-3, 60 minute Acute Exposure Guideline

Plywood (Interior and Exterior)

Plywood sheathing/decking

Which Chemicals Does Plywood Offgas?

Exterior plywood

Exterior grades of plywood are used for roof sheathing, subfloor, and roof decking. Exterior grades of plywood are made with phenol-formaldehyde as the binder/glue. Plywood is made with 3.5% formaldehyde. Phenol formaldehyde is the least toxic type as it offgases less and it offgases faster.

Exterior plywood is also be called structural plywood or softwood plywood (SWPW).

Type of wood

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It is made of softwood, usually fir, spruce and/or pin). In Canada, Douglas Fir Plywood (DFP) (can have up to 21 other species of woods in the inner plies), and Canadian softwood plywood (CSP) may have balsam poplar, trembling aspen, and cottonwood.

Formaldehyde

When the American Plywood Association (APA) tested formaldehyde levels of new exterior plywood they started out below 0.1 parts per million (ppm). But “emissions rapidly approached zero as the panels aged. In fact, the levels were so low and so close to the ‘background’ levels in the test chamber that it was not possible to measure them accurately” source APA. While the APA would not say exactly when the PF levels approached 0 (or close to it), this is the study that changed my thinking about avoiding plywood in a new build. For most people, exterior plywood in a build will be sufficiently offgassed by the time the building is complete.

Testing your reactions

If you are extremely sensitive you should test out plywood when new, after a few weeks and after 2-3 months of airing. You should also compare that to OSB, to see which is better for your health. I generally prefer plywood. My post on sheathing goes into more detail on alternatives if you need to avoid both plywood and OSB.

CDX plywood

CDX is a type/grade of exterior plywood used for sheathing with an Exposure level of 1 other types ending in X are also made for the exterior.

Marine-grade plywood

In the US the marine-grade plywood I’ve seen contains PF, but they can use other glues as well.

This is not a specific type of plywood in Canada.

Grades of Plywood

These are grades of Plywood in the US. And here are grades of plywood in Canada.

Pressure-Treated Plywood

Pressure-treated plywood is commonly is treated with alkaline copper quaternary (i.e. copper and quaternary ammonia) (ACQ). Copper Azole (CBA) is another type, which contains copper, tebuconazole, and possibly boric acid. Though some wood is still treated with chromated copper arsenate (CCA), this is rare nowadays and it’s definitely not often used in residential buildings.

Interior Plywood

Interior grades of plywood were often is made with urea-formaldehyde as the adhesive. Urea-formaldehyde (UF) offgasses more and for longer. Now, phenol-formaldehyde (PF) is more standard. Interior plywood is often called furniture grade or hardwood plywood. You will want to make sure your furniture is made with PF or NAF glues, not UF. Interior plywood is made of hardwoods (usually) of various types, though it can be made of softwood like cedar. When folks talk about formaldehyde-free plywood, this is the one they are referring to. Their adhesive is partially proprietary, but they claim it is “soy-based”. The full Declare label is here but this doesn’t tell us much about what it will offgas in the end, only what went into it. I have seen chemically sensitive folks react to this brand of plywood so I would make sure to test it out yourself before using it. Purebond plywood is “interior grade”, it is not structural and it is not made to hold up to high humidity or moisture. Folks are using this improperly when using it as sheathing and roof decking. For those less sensitive Purebond is a good choice for furniture and cabinets. You can find it as a component of many preferred kitchen cabinets companies here. You can buy it at Home Depot and Amazon.

Medium Density Fiberboard (MDF)

Primed MDF boards

Which Chemicals Does MDF Offgas?

MDF is often made with urea-formaldehyde which offgasses more than phenol-formaldehyde. MDF is composed of 10% formaldehyde, but because of its density, it’s slower to offgas than plywood or particleboard.

Where it’s used

You will find MDF in many cabinets, solid-core and hollow core doors, furniture, and as part of some flooring types. MDF is also used in baseboards and other trim which can easily be swapped out for solid wood.

My posts on kitchen cabinets, furniture, doors, and flooring provide alternatives.

Glues and offgassing

The level of formaldehyde offgassing is higher than in plywood, even if both are CARB 2 certified – 0.11 ppm in MDF compared to 0.05 ppm for plywood. MDF made with formaldehyde should be avoided where possible in a healthy home.

Formaldehyde-Free MDF

There are brands of no added formaldehyde MDF that may be used by some specialty furniture makers, but it is not what you will commonly see.

The main alternative glue is MDI.

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See my post on formaldehyde-free MDF for brands.

Oriented Strand Board (OSB)

OSB sheathing

Which Chemicals Does OSB Offgas?

OSB is usually made with phenol-formaldehyde (PF) and MDI adhesives. MDI is the primary adhesive in OSB usually. Though they claim the MDI fully cures into a polyurethane, there is evidence MDI offgases isocyanates. I certainly pick up the offgassing for months.

Where is it used

OSB is often used in house sheathing: roof sheathing/decking, exterior wall sheathing, and as subfloors. Usually OSB and plywood can use used interchangeably for applications in a building. Sensitive folks usually choose plywood over OSB, but some brands of OSB listed below can be very good. A common type of OSB is the Huber Advantech. I find these need a solid 4 months to offgas to my standards (a lot longer than plywood).

Wood types

OSB is made from either hardwoods or softwoods. The most commonly used softwoods for manufacturing OSB are pines/firs/spruce. Aspen is the most commonly used hardwood. In the US look for APA stamped OSB which will not contain UF.

There is no added formaldehyde (“formaldehyde-free”) OSB, but it’s harder to source.

Particleboard/Low-Density Fiberboard (LDF)

Particleboard laminated with melamine plastic

Which Chemicals Does Particleboard Offgas?

Urea-formaldehyde (UF) (the type that offgasses more and for longer) is usually used as the adhesive in particleboard, which is also called furniture board. You may also see MDI used. Particleboard is made with 12.4% formaldehyde, however because it’s lower density than MDF or HDF, it does offgas a little bit faster in my experience.

Where is it use

Particleboard is commonly used in cabinets and to make furniture. It is often used to make shelving and for structure in inexpensive beds and sofas. When the material is listed as “laminate” this is particle board with a melamine plastic laminated onto it like in the picture above. For safer options, see my posts on healthier cabinet options, furniture, sofas, and sealing in the offgassing in your particleboard.

High-Density Fiberboard (HDF)

Pegboard which is made of HDF

Which Chemicals Does HDF Offgas?

Hardboard/HDF/fiberboards could be made with either phenol-formaldehyde, urea-formaldehyde, or melamine formaldehyde.

Paraffin wax and a small amount of ammonia are typical additives. Linseed oil can be added to some types. HDF is used in the substrate of many floorings like Marmoleum Click, some cork flooring, and laminate flooring (you can identify whether you have flooring with HDF by checking out this post). It is also used to make Masonite and other brand hollow core doors (as the skin). It’s often found as the backing to furniture, like dressers, bookcases, and cabinets. Pegboard (pictured above) is also made from HDF. When used as a backing to furniture it’s easy to seal in almost all of the formaldehyde with shellac.

Structural Engineered Beams and Which Chemicals They Offgas

TGI Joists

Glulam, PSL, LVL are usually made with phenol-formaldehyde (PF).

PF is also used for finger joining stress graded lumber.

TGI/TJI Joists are made with PF and MDI glues.

Cross-laminated timber can be made with a variety of different glues: polyurethane, polycarbonate, isocyanate (EPI), melamine, or phenolic adhesives. The most common adhesives are formaldehyde-free – polyurethane or EPI. With polyurethane being the most common. LSL is mainly made with the adhesive MDI and I have seen a small percentage of undisclosed binders.

i beams are made of steel

To avoid laminated wood beams you will have to consider that decision in the very initial planning and design of your house. See this post on considerations that need to be made early in the build for the chemically sensitive.

Brands of Plywood and OSB and Which Chemicals They Use as Glues

Norbond Trubond – PF and MDI

Aventech Roof OSB – PF and MDI

Avantech Subfloor – PF and MDI (claims to be lower-emitting that typical OSB)

Ultrastock MDF – UF

Medex and Medite II by Roseburg – No formaldehyde MDF

Purebond Plywood – No added formaldehyde, proprietary glue used

Roseburg – Only lists PF as glue

Zip Systems – Phenol formaldehyde and MDI

Georgia Pacific DryGaurd claim to be lower-emitting than typical OSB

Corinne Segura is a Building Biologist with 8 years of experience helping folks 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!

Additional Sources:

mychemicalfreehouse.net - Chemical Offgassing from Pressed & Laminated Wood Products

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