Chemical Offgassing from Pressed Wood and Laminated Wood Products

A Guide to Choosing Pressed Wood and Laminated Wood Products for those Avoiding Formaldehyde and Chemicals

This post will cover pressed wood and laminated wood (engineered wood) products used in building and in household items like furniture and doors. We are going to look at the adhesives they use, which chemicals are used as the binder/adhesive, and what do they offgas. I will also note which wood types are commonly used.

This is going to be the adhesives used in the US and Canada. Europe will be similar but may have better regulations in some areas. Other parts of the world may use different adhesives.

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.

First a List of Adhesives used in Engineered Wood Products 

MDI methylene diphenyl diisocyanate - offgasses methylene diphenyl diisocyanate, though the companies claim this cures into a polyurethane.

PF Phenol Formaldehyde - 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.

UF Urea Formaldehyde - This is the type of formaldehyde that offgasses in higher amount 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.

NAUF No added Urea Formaldehyde essentially means PF is used.

NAF No added formaldehyde, this means no formaldehyde is added to the product. They cannot be called formaldehyde-free because wood naturally contains formaldehyde. No added formaldehyde products are often made with MDI or "soy based glue".

Soy Based Glue - we don't know what is in a soy based glue, just like soy based foam which is mostly polyurethane, saying something is soy based does not tell us that much about it potential offgassing and toxicity.

How Much Formaldehyde is Acceptable for those Avoiding Toxins?

Product Certifications for Formaldehyde Levels:

What does CARB II mean, how much formaldehyde does this allow?

CARB II is a standard set by California for products sold there, but many products across North America comply with this requirement.

Products measured include those containing hardwood plywood, medium-density fiberboard, and particleboard - these are pressed wood products sold for indoors, it does not include exterior sheathing products like exterior plywood and OSB.

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-1 and E-2 European Formaldehyde Levels Standard

E1 certifies that boards release less than 0.1 ppm (parts per million) and for E2 boards 0.1 ppm and 0.3 ppm.

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

How do you interpret these levels? 

Formaldehyde is naturally occurring in wood and outside air. In fact 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 in the outside air and is always in the outdoor air whether you are rural or urban.

The rate of formaldehyde in outdoor air is about 0.0002-0.006 ppm in rural and suburban outdoor air, 0.0015-0.047 ppm in urban outdoor air Source. Another source sites the average level in U.S. urban areas is 0.011 - 0.02 ppm. The major sources are power plants, manufacturing facilities, incinerators, and automobile exhaust emissions. Source

Average indoor levels range from 0.020-4 ppm in indoor air Source.

Formaldehyde Reference Levels

Level                    Reference

0.0002-0.006        Rural and suburban outdoor air
0.0015-0.047        Urban outdoor air
0.0073 ppm          GreenGuard Gold levels for products
0.020-4 ppm         Average levels in conventional homes/indoor air
0.04 ppm Health 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) - Which Chemicals does it Offgas?

"pete's plywood" doublebug
CC BY-NC-SA 2.0 

Exterior plywood is used for roof sheathing, subfloors and roof decking. Exterior grades of plywood is made with phenol formaldehyde as the binder/glue. Phenol formaldehyde is the least toxic type as it offgasses less and it ofgasses faster. Exterior plywood can also be called structural plywood or soft wood plywood (SWPW). It is made of softwood, usually fir (or spruce, pine). 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.

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 is 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 on 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.

If you are extremely sensitive you should test out plywood when new, after a few weeks and after 2-3 months of offgassing. 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 - 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, marine grade I’ve seen contains PF, but can use other glues as well. This is not a specific type of plywood in Canada.

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

Pressure treated plywood commonly is treated with Alkaline copper quaternary (ACQ), Copper Azole (CBA) is another type, which contains copper, tebuconazole, and possibly boric acid. Though some is still treated with Chromated copper arsenate (CCA), this is not commonly used in residential buildings.

Interior plywood was often is made with urea formaldehyde as the adhesive. Urea formaldehyde (UF) offgasses more and for longer. Now, phenol formaldehyde 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 not UF or with NAF glues.

Interior plywood is made of hardwoods (usually) of various types, though it can be made of softwood like cedar.

Purebond no Added Formaldehyde Plywood - Purebond Plywood is widely known as the healthier alternative to interior grade plywood. Their adhesive is proprietary, but they claim it is "soy based". I have seen chemically sensitive folks react to this brand of plywood so I would make sure to test it out yourself before using. Purebond plywood is interior grade, it is not structural and it is not made to hold up to high humidity. 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) - Which Chemicals does it Offgas?

MDF is usually made with urea formaldehyde which offgasses more than phenol. You will find MDF in cabinets, solid-core and hollow core doors, furniture and as part of flooring such as some laminates. My posts on kitchen cabinets, furniture, doors, and my post on flooring provide alternatives. MDF is also used in baseboards and other trim which can easily be swapped out for solid wood.

There are brands of no added formaldehyde MDF that may be used by some speciality furniture makers but it is not what you will commonly see. The levels of formaldehyde offgassing are higher in MDF 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.

Oriented Strand Board (OSB) - Which Chemicals does it Offgas?

By Boatbuilder  CC BY-SA 3.0

OSB is usually made using phenol formaldehyde (PF) and MDI as the adhesive (MDI primarily in OSB though they claim the MDI fully cures into a polyurethane). MDI offgases isoynates. OSB is often used in house sheathing -roof sheathing/decking, exterior sheathing and in floors (subfloors). Usually OSB or plywood can use used interchangeably for the same application in building. Sensitive folks usually choose plywood over OSB, but some brands of OSB listed below can be very good.

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 used in OSB.

In the US look for APA OSB which will not contain UF. There is no added formaldehyde OSB but they may be harder to source.

Particle board/Low Density Fiberboard (LDF) - Which Chemicals does it Offgas?

Source CC BY-SA 3.0

Urea formaldehyde (UF) is usually used as the adhesive in particle board. You may also see MDI used. Particleboard can be used in cabinets and in some inexpensive furniture. For safer options, see my posts on kitchens and furniture.

Structural Beams and which Chemicals they Offgas

Glulam, PSL, LVL are usually made with phenol formaldehyde. PF is also used for fingerjoining stress graded lumber. TGI beams are made with PF and MDI glues. Cross laminated timber can be made with a variety of different glues (but not urea formaldehyde). 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.

By Brand:

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 formaldhyde, proprietary glue used
Roseburg - only lists PF as glue
Zip Systems - Phenol formaldehyde and MDI
Georgia Pacific DryGaurd (what glue?) claim to be lower emitting than typical OSB.

Additional Source:

https://www3.epa.gov/ttn/chief/ap42/ch10/final/c10s06-1.pdf

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

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