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Re: GBlist: GB List: OSB question
Please excuse a rant, but a very hot button of mine has been pushed. I have
worked for 14 years to establish standard methods for sampling and analysis
of indoor air so that measurements from various labs and buildings could be
compared. One of the most important standards applies to emisssions testing,
since we need to know source strengths (contributors to contaminant loads)
to design buildings reliably and effectively.
So......PPM, or parts per million, is not an emission rate, it is a
concentration. The wood products industry has reported emissions this way
for some time - back into the early 80s at least - but, to my knowledge, it
is unique, with the possible exception of Underwriters Laboratory, which
reports ozone emissions from photocopiers in ppm or (ppb) also. This sort of
reporting simply does not tell the users of the test results what the
emission rate is. You must know the loading factor - in the case of
composite wood products, the area of the emission source per volume of the
test chamber - and the ventilation rate to be able to calculate an emission
factor or emission rate. In the case of a machine such as a photocopier, you
must know the copy rate and air exchange rate in the test chamber.
An emission rate must be stated in mass units per unit of time. For sheet
materials such as composite wood panels, a unit of area should also be
given. This might be called an area specific emission rate, or a normalized
emssion rate. So, the formaldehyde emission rate from composite wood
products would be stated in micrograms or milligrams of formaldehyde per
square meter per hour -- µg/m^2-h. If you are interested in the details of
emissions testing and the reporting and meaning of results, consult ASTM
Standard D5116-90. Although it has been revised recently and the revision is
currently being balloted, the original standard is the most authoritative
guide to emissions testing available. Copies can be obtained from ASTM at
610 832 9500.
For the computationally inclined lister, the formula is
EF = C(Q)/A
EF = emission factor, mg m^-2 h^-1,
C = equilibirum changer concentration, mg/m^3,
Q = flow through chamber, m^3/h, and
A = sample area, m^2.
An equivalent expression is also used:
EF = C(N/L)
N = chamber air exchange rate, h^-1
L = chamber loading, m^2/m^3.
Note that N = Q/V, where V = chamber volume, m^3.
An emission rate would involve multiplying the area of source material times
the emission factor, and would be stated in units of mass per unit time.
At 10:50 AM 5/8/97 -0700, you wrote:
>John A. Emery of the American Plywood Association wrote a paper on
>formaldehyde in composite wood panels made with phenolic resin, "Structural
>Wood Panels and Formaldehyde", that you can request from APA at
>(206)565-6600. It reports on formaldehyde emission levels found using a
>test chamber procedure. The test procedure seems reasonable, except for the
>fact that the ventilation rate was somewhat high. Allowing for that, the
>emissions levels reported from new boards was under 0.1 ppm.
>>Can anyone provide accurate information regarding the harmfulness of
>>phenol formaldehyde in building materials?
>O'Brien & Associates
>Environmental Building Consultants
>Portland General Electric Earth Smart program
>This greenbuilding dialogue is sponsored by Oikos (www.oikos.com)
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Hal Levin <email@example.com>
This greenbuilding dialogue is sponsored by Oikos (www.oikos.com)
and Environmental Building News (www.ebuild.com). For instructions
send e-mail to firstname.lastname@example.org.