Engineered wood products and formaldehyde emissions

Although modern engineered wood materials have been around for over half a century, many people still have misconceptions about these high-strength, high-stability composite wood products. Especially in the environmental field, influenced by some low-grade, questionable-quality plywood products, the public generally views engineered wood materials, which use glue as the main adhesive, with great apprehension. The biggest concern revolves around formaldehyde emissions from composite engineered wood products. Today, we'd like to provide a simple explanation of this topic.

What are engineered wood materials?

In simple terms, engineered wood materials refer to a range of large-format or large-format architectural or decorative components made by gluing, finger-jointing, or laminating small-sized timber or wood chips using engineering processing methods. Common engineered wood materials include: glued laminated timber beams and columns, cross-laminated timber (CLT), OSB (Oriented Strand Board), Plywood, LVL (Laminated Veneer Liner), I-joist beams, and many other products. These products generally rely on high-strength structural adhesives to bond the timber. Now, some engineered wood materials also use metal fittings or even dowel systems for connection, such as NLT (Nail-Jointed Laminate) and DLT (Dowel-Jointed Laminate).

Known for its use in striking projects such as vaulted ceilings and other spacious designs, glued laminated timber (GLLT) is frequently used in churches, schools, hotels, and other commercial buildings due to its aesthetic appeal and strength. Indeed, GLLT possesses a timeless charm with its quintessential natural wood appearance. GLLT products, such as CLT, are becoming a mainstay in multi-story and high-rise timber structure projects, showing a growing trend of challenging traditional concrete materials. OSB is also one of the most widely used structural panel materials; its stable shear properties make it a primary cladding material for lightweight timber flooring, walls, and roofs.

What is formaldehyde?

Formaldehyde is a simple chemical substance composed of hydrogen, oxygen, and carbon. It is produced naturally and is a product of many natural processes. It is produced by our bodies and exists in the air. Plants and animals also produce formaldehyde. Formaldehyde is found in many fruits and vegetables and is a byproduct of cooking certain vegetables such as kale and cabbage. This chemical breaks down quickly and is metabolized into simple carbon dioxide. Our bodies easily break down the low amounts of formaldehyde we are exposed to every day.

Formaldehyde is also a combustion byproduct associated with the burning of kerosene and natural gas, automobile exhaust emissions, and cigarette smoke. It is an important industrial chemical used in the manufacture of many consumer products, including wrinkle-free fabrics and even toothpaste.

How much formaldehyde is in wood?

All wood species, and all wood products, contain and release trace amounts of formaldehyde. Because formaldehyde is naturally present in wood, there is no such thing as "zero-formaldehyde" wood. For example, an oak tree emits 0.009 parts per million of formaldehyde. On its own, this is a very low amount, but dense forests can have much higher concentrations. Therefore, any wood cut from an oak tree contains trace amounts of formaldehyde, and the same is true for all wood products.

Formaldehyde emission regulations

According to the website of the Canadian federal government's Environment Agency, all composite wood products manufactured and sold in Canada must comply with a series of federal and provincial environmental regulations. The Canadian government is also considering incorporating CSA standards into the regulations to more strictly manage emissions from composite wood products. CSA stands for Canadian Standards Association. Founded in 1919, it is Canada's first non-profit organization dedicated to setting industry standards. Electronic, electrical, bathroom, and gas products sold in the North American market require safety certification. Currently, CSA is Canada's largest safety certification body and one of the most renowned safety certification bodies in the world.

According to information from the APA, the world's largest engineered wood products organization, the manufacture of structural wood products such as structural plywood and oriented strand board (OSB) meets stringent product standards, including the voluntary product standard PS 1-07 for structural plywood and the voluntary product standard PS 2 for performance standards of wood-based structural panels. Because wood products are manufactured according to these standards, they are made using only moisture-resistant adhesives when applied to construction to meet the Exterior or Exposure 1 exposure level for outdoor use. These adhesives, including phenolic resin adhesives and isocyanate (MDI) adhesives, undergo a chemical reaction to achieve a stable bond during thermoforming. This results in final products with low formaldehyde emission levels, meeting or exceeding internationally recognized formaldehyde emission standards and regulations.

1. U.S. Department of Housing and Urban Development Prefabricated Housing Standard. This standard specifies an emission limit of 0.20 ppm for non-structural plywood evaluated using the American ASTM E1333 method. Due to its extremely low formaldehyde emissions, phenolic-bonded structural plywood is exempt from testing and certification. While there are no specific restrictions on oriented strand board (OSB), it is widely accepted that phenolic adhesives used for the face panels can also be used on OSB products that comply with the voluntary product standard PS 2.

2. California Air Resources Board (CARB) Comprehensive Measures for the Prevention of Air Toxicity from Wood Products. This regulation, developed by the California Environmental Protection Agency and scheduled to take effect on January 1, 2009, is considered the strictest regulation on formaldehyde emissions in the United States. Recognizing the different forms of formaldehyde in wood products, Regulation 8 explicitly exempts “structural plywood,” “different types of structural panels,” “structural composite wood,” “oriented strand board,” “glulam,” and “precast I-beam joists.”

3. According to Japanese Agricultural Standards (JAS), wood-based structural panels must meet the most stringent formaldehyde standard (F★★★★), using the JIS A 1460 testing method, with an average emission level below 0.30 mg/L. PS1 and PS2 panels easily meet the F★★★★ requirement. This formaldehyde emission regulation for wood-based structural panels is widely recognized as one of the strictest in the world.

4. Oriented strand board (OSB) sold in the European market must meet EN 300 standards and have its formaldehyde emissions classified using the EN-717-1 formaldehyde testing laboratory method. Structural plywood sold in Europe must comply with EN 636 and have its formaldehyde emissions assessed according to EN 717-1. Structural plywood and OSB manufactured with PS1 and PS2 panels must meet the E-1 formaldehyde emission limit of 0.124 mg/m³ in these standards.

Some information is from: APA Engineered Wood Association