Surface Coating of Miscellaneous Metal Parts
and Products
NESHAP Summary
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2. What Are the HAP Emissions and What Are the Primary Sources
of Emissions for Facilities Affected by this Rule?
The final NESHAP regulates emissions of organic HAP. Available
emission data collected during the development of the final
NESHAP show that the primary organic HAP emitted from the
surface coating of miscellaneous metal parts and products
include:
- Xylenes,
- Toluene,
- MEK,
- Phenol,
- Cresols/cresylic acid,
- Glycol ethers (including EGBE),
- Styrene,
- MIBK, and
- Ethyl benzene.
These compounds account for approximately 90 percent of this category’s
nationwide organic HAP emissions.
Health and Environmental Risk Assessment Resources
Search the following sites for more information on the HAP listed above.
US
EPA HAPS Health Effects Notebook
US
EPA Integrated Risk Information System
University
of Vermont Safety Resources
NIOSH
Pocket Guide to Chemical Hazards
WISER -
the Wireless Information System for Emergency Responders
 The majority of organic HAP emissions from
a facility engaged in miscellaneous metal parts and products
surface coating operations comes from the application,
drying, and curing of coatings. The remaining emissions
are primarily from cleaning operations. In most cases,
organic HAP emissions from mixing, storage, and waste
handling are relatively small. The organic HAP emissions
associated with coatings (the term ‘‘coatings’’ includes
protective and decorative coatings as well as adhesives)
occur at several points. Coatings are most often applied
either by using a spray
gun in a spray booth or by dipping the substrate in a
tank containing the coating. In a spray booth, volatile
components evaporate from the coating as it is applied
to the part and from the overspray. The coated part then
passes through an open (flashoff) area where additional
volatiles evaporate from the coating. Finally, the coated
part passes through a drying/ curing oven, or is allowed
to air dry, where the remaining volatiles are evaporated.
 Organic HAP emissions also occur from the activities
undertaken during cleaning operations, including paint
stripping, where solvent is used to remove coating residue
or other unwanted materials. Cleaning in this industry
includes cleaning of spray guns and transfer lines (e.g.,
tubing or piping), tanks, and the interior of spray booths.
Cleaning also includes applying solvents to manufactured
parts prior to coating application and to equipment (e.g.,
cleaning rollers, pumps, conveyors, etc.).
Mixing and storage are other sources of emissions. Organic
HAP emissions
can occur from displacement of organic vapor-laden air
in containers used to
store HAP solvents or to mix coatings containing HAP
solvents. The displacement of vapor-laden air can occur
during the filling of containers and can be caused by
changes in temperature or barometric pressure, or by
agitation during mixing.
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