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Subject: Air quality

Air quality

From: Jean Tetreault <jean_tetreault>
Date: Wednesday, December 24, 1997
Reply to Ramona Duncan-Huse about monitoring air quality in a new
facility. As first good steps you specified non-urea formaldehyde
based adhesive for the wood products and asked for technical data
or/and materials safety data sheet (MSDS) for the various building
materials.  In the section on Flammability of the MSDS (or Hazardous
decomposition products), combustion products are sometimes specified
in the MSDS which gives hints on presence of contaminants. If sulfur
compounds (SO2, H2S and H2SO4) are specified as combustive products,
materials can be automatically rejected. Tests can be done for all
materials with different spot tests including accelerated corrosion
test such as Oddy test. This test can give some false positive
results but little false negative results.

Based on my knowledge thin films such as paints, sealers and
adhesives will release most of their volatiles into a month with a
normal HVAC system (when no important chemical reaction is involved
such as oxidation of unsaturated linkage in oil based paints). Thick
materials with free volatiles such as particle board glued with urea
formaldehyde will take few months to release all the free
formaldehyde. After these periods, both thin and thick materials
will release volatiles but at very small levels. This may be due to
the tale of the volatiles emission exponential decay or/and emission
of volatiles from degradation process of the materials (oxidation,
hydrolyse, etc). The question coming is are these emissions
dangerous to artefacts in my specific case (display case, cabinet
room)?

We need reliable methods to measure volatiles levels and need to
know the sensibility of artefacts to these volatiles. Some reliable
and expensive methods of measurement and some standard for air
quality for archival materials (SO2, NO2, O3) exist. These standards
for air quality are based either on what the best technology can
offer or on background levels of these pollutants in non
urban/industrial environment. No (largely recognize) standard for
indoor generated pollutants such as formaldehyde and acetic acid
exist except "use best control technology". For these indoor
pollutants, "experts" in indoor pollution and conservators are
facing the challenge of the estimation of the level of pollutant to
recommended as safe levels. In theory, any presence of pollutant can
induce a damage, hence lower levels are the best. On the other hand,
managers want to know the levels of volatiles which they should not
exceed in their museums to establish their policies based on
feasible criteria.

I think a "Forum on Air Quality Criteria for Indoor Pollutants"
should be established. We can consider criteria for mixed
collections or for different artefact categories (metal,
cellulose...). These criteria can be established by considering
these elements: clean background levels, outside levels, results
from non accelerated damage test, threshold (level of volatile which
there is no expected significant effect), limit of detection of
analytical methods and risk assessment. A security factor as for the
food legislation (1/100 of the volatiles levels known to be harmful)
or health legislation can be also examined as a possibility. Of
course, these criteria could be readjusted in the future according
to updated data. I am hoping that this topic can be considered at
the meeting that Dr. Lorraine Gibson at the University of
Strathclyde, Glasgow <l.t.gibson [at] strath__ac__uk> plans to organize in
mid-April on "Standardising Methods for Materials Testing in the
Museum Environment". However, I admit that Standardising Methods is
important and complex subject enough to required to two full days.
Criteria for indoor pollutant may need a separate meeting.

Jean Tetreault
Conservation Scientist
Preventive Conservation Services
Canadian Conservation Institute
1030 Innes Road, Ottawa (Ont)
K1A 0M5 Canada

                                  ***
                  Conservation DistList Instance 11:58
                Distributed: Wednesday, January 7, 1998
                       Message Id: cdl-11-58-002
                                  ***
Received on Wednesday, 24 December, 1997

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