Environmental Engineering Reference
In-Depth Information
1.
Diffusion barriers and surface coatings
Several source treatment techniques for HCHO emissions from pressed
wood products have been evaluated and received limited use in reducing
residential HCHO levels. European investigators have evaluated the efficacy
of surface treatments and barriers on HCHO emissions from particle board
under laboratory chamber conditions. Significant reductions in emissions
were observed for vinyl floor covering, vinyl wallpaper, HCHO-scavenging
paints, polyethylene foil, and short-cycle melamine-formaldehyde paper.
Effectiveness was, however, observed to decrease with time. Several U.S.
studies evaluated the effectiveness of potential HCHO barriers placed on
particle board underlayment in controlled whole-house conditions. Vinyl
linoleum and 6-mil polyethylene sheeting were observed to be effective
HCHO barriers, resulting in a reduction of emission rates and air concen-
trations on the order of 80 to 90%. The effectiveness of several finish coatings
and HCHO-scavenging paints applied to particle board underlayment under
whole-house conditions were evaluated in other studies. Treatment effec-
tiveness was highest for two applications of nitrocellulose-based brushing
lacquer (70%), followed by alkyd resin varnish (53%), and polyurethane
(43%). Variable performances were observed when three specially formu-
lated HCHO sealant coatings were evaluated. The most effective product
was observed to reduce whole-house HCHO levels by 78 to 87% on a long-
term basis with but one application. Another was less effective (57 to 67%),
and a third was ineffective with one application but reduced HCHO con-
centrations by 65% after two applications.
Based on these studies, it appears that source treatment in the form of
surface coatings and physical barriers can reduce indoor HCHO levels asso-
ciated with particle board underlayment. Such measures have not been eval-
uated for more complex HCHO-emitting sources such as kitchen and bath
cabinetry, workstations, desks, furniture, tables, storage cabinets, etc. These
materials are, in many cases, covered with paper overlays, vinyl coatings,
plastic laminates, or clear finish coatings. They also contain raw surfaces
including numerous joints which are not accessible to treatment. Wood furni-
ture and cabinetry are often coated with acid-cured finishes which are signif-
icant sources of HCHO. It is unlikely that source treatment would be effective
in controlling HCHO emissions from such complex sources in buildings.
2.
Ammonia fumigation
During the late 1970s and early 1980s, Weyerhauser Corporation, a major
wood-products manufacturer, developed and evaluated a technique for
reducing HCHO levels in mobile homes based on the principle of using
gaseous ammonia (NH
) to react with HCHO and methylol end groups in
U-F bonded wood products. On reaction with NH
3
, free HCHO in the resin
(as well as that which was airborne) formed hexamethylene tetramine. Meth-
ylol end groups on the U-F polymer were stabilized and were less susceptible
to hydrolysis.
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