Questions About Trus Joist Products

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Formaldehyde Emissions

What is the level of formaldehyde emissions from our products?

It is less than 0.10 ppm. The wood-based composite products, which are manufactured or used by Trus Joist-Microllam® LVL, TimberStrand® LSL, Parallam® PSL, plywood and oriented strandboard-are bonded with either resorcinol, phenol formaldehyde or polymeric MDI (isocyanate) adhesives, or a combination of these.

Independent third-party testing (Structural Board Association Technical Bulletin,dated November 15, 1990, and American Plywood Association, 1986) shows that using these adhesives does not result in a significant increase in the formaldehyde emissions from composite products as compared to solid lumber products. When tested in accordance with the ASTM E 1333 standard, Determining Formaldehyde Levels from Wood Products Under Defined Test Conditions Using a Large Chamber, the formaldehyde emissions of these products are below 0.10 ppm, which is recognized as the maximum limit by the most stringent regulators.

In many cases, the emissions are so low that they cannot be distinguished from the background level of formaldehyde in the fresh air used during testing.

Regulations

Are there regulations specifying the maximum formaldehyde emissions from our products?

In the U.S. and Canada there are no standards or regulations governing the formaldehyde emissions from our products. It is worth comparing the emissions from our products to standards for other products. The voluntary industry standard, ANSI 2098.1 (1993) Particleboard, sets the maximum formaldehyde emissions at 0.20 ppm for particleboard decking and underlayment, neither of which are manufactured by Trus Joist. These composite products are usually bonded with urea formaldehyde adhesive, which more readily releases formaldehyde compared to phenolic adhesives.

In Germany, the E-1 standard sets a maximum limit of 0.10 ppm for formaldehyde emissions from many types of wood-based composite products. We meet this standard. This is important, not only for German customers, but for U.S. customers who export products to Germany.

Dangerous Levels

Can formaldehyde emissions build up to "dangerous" levels in a home?

This is unlikely. Although a new home contains many sources that emit formaldehyde-such as drapes, upholstered furniture, latex paint, carpet, cabinets, furniture and others-the rate of formaldehyde emissions from these products decreases quite rapidly during the first 30 days. In addition, most homes have an average of 0.3 to 0.5 air changes per hour, which is sufficient to dissipate the small amount of formaldehyde.

Adhesive in Composite Products

How much adhesive is used in TJ's composite products?

Our engineered wood products (and those we purchase) normally contain less than 6 percent adhesive solids by weight.

Polymeric MDI

What is the risk of a mill worker being sensitized to polymeric MDI?

Newspapers have reported instances of mill workers being sensitized to polymeric MDI (isocyanate) adhesive during the manufacturing of oriented strandboard and engineered strand products

Since TimberStrand® LSL uses this adhesive type, do end users who handle or work with TimberStrand® LSL or who occupy buildings constructed with TimberStrand® LSL need to be concerned about becoming sensitized?

No. During the TimberStrand® LSL manufacturing process, the isocyanate adhesive is "cured", which means that it chemically changes to an inert compound that cannot sensitize people. As always, secondary manufacturers cutting and machining wood or wood-based products, including TimberStrand® LSL, must control dust and fine particles as required by OSHA (and other regulations).

Questions and Answers About Smoke Toxicity and Fire Performance

Combustion Gases

Is the toxicity of combustion gases (smoke) from TJ's composite products greater than that for solid wood?

No. Smoke from solid wood and wood composites have the same toxicity.

Testing shows that the smoke from Microllam® LVL, Parallam® PSL, TimberStrand® LSL, plywood, and oriented strandboard is not more toxic than that from solid wood products.

The small amount of adhesive used in these composite products does not increase the toxicity of smoke or the amount of smoke when compared to solid wood.

Adhesives and Fire

Do the adhesives used to make Microllam® LVL, TimberStrand® LSL, Parallam® PSL, oriented strandboard, and plywood soften during a fire?

No. Resorcinol, phenol formaldehyde, and polymeric MDI (isocyanate) adhesives are thermosetting. This means that once they are cured to a hard substance during the manufacturing process, they do not soften or relax when subsequently exposed to elevated temperatures.

Like wood, the adhesives are char-forming compounds. Of course, if the intensity and duration of a fire is sufficient, these adhesives, as well as the wood, will be consumed.

Although it is probably not a practical consideration since most fires are quite hot, the wood component of these composites will ignite at about 450° F (232° C) while degradation of the adhesive will occur between 750° F and 1,110° F (400° C to 600° C).

Adhesives, Combustibility, and Smoke

Do the adhesives used in TJ's products increase the combustibility? Do they increase the amount of smoke?

No. The adhesives do not increase the combustibility of composite products or the amount of smoke produced during burning compared to solid wood products.

Member Substitutes

Can an equivalent size member of Microllam® LVL, Parallam® PSL, or TimberStrand® LSL be substituted for dimensional lumber in a fire-rated system?

The fire resistance of Parallam® PSL and Microllam® LVL is considered equivalent to similar sizes of solid-sawn lumber (see NER-292 and NER-126) when Type 4 (BOCA National Building Code), Type III (Standard Building Code), or Type IV (Uniform Building Code) heavy timber construction is required.

There has been no ASTM E 119, Fire Test of Building Construction and Materials, fire tests conducted using Microllam® LVL. It is our belief that they would produce results very similar to assemblies containing solid-sawn members of similar size.

Parallam® PSL has been tested according to the CCMC Guidelines, Test Method for Evaluation of Structural Composite Beams in Fire Resistive Timber Construction, which uses the standard time-temperature profile in ASTM E-119 and was found to exceed the models for estimating structural strength of the remaining section.

TimberStrand® LSL has been tested to the ASTM E 119 criteria and found to be equivalent to solid-sawn lumber when used in fire-rated assemblies.

The local building inspector should be contacted for approval of specific assemblies.

Flame Spread Issue

Why is flame spread an issue?

Generally, the flame spread rating is not an issue when using our engineered wood products since they are typically used as structural supporting members rather than surface covering materials.

The speed at which a fire travels through a room or building influences the ability of people to escape. Therefore, the code agencies have requirements for the surface burning characteristics of wood used in building

Class I flame spread will be required in situations that are most critical to human safety. See, for instance, 1994 UBC-Section 804, 1996 NBC-Section 803, 1994 SBC-section 803, and the 1995 NBCC-Section 3.1.12.

Flame Spread Rating

What is the flame spread rating of our products?

Our products, as well as most untreated wood products (solid wood and wood composites), are rated as Class III.

The flame spread rating is determined by the ASTM E 84 or CAN/ULC-S102.2 test methods and is a measure of how quickly a flame travels along the surface of a material once ignited. There are three classes: Class I (or A), Class II (or B), and Class III (or C). Class I indicates how slow a flame moves across a surface; and Class III indicates how fast a flame spreads across a surface.

Hazardous Ingredients

Microllam® LVL, Open-Web Trusses, Parallam® PSL, TimberStrand® LSL, and TJI® Joists contain no hazardous materials; however, OSHA considers wood dust, which may be generated during subsequent re-manufacturing, to be hazardous.

Wood dust from machining, sanding, or sawing is a composite of approximately 90 to 100% wood (e.g., aspen, Douglas fir, southern pine, western hemlock, yellow popular) and up to 10% cured adhesive (PF, PRF, MDI) and wax solids.