Environmental Engineering Reference
In-Depth Information
plaints. A variety of measures may be employed on a generic basis or applied
to specific contaminant problems. These include source removal and replace-
ment, source treatment and modification, and climate control.
A. Source removal and replacement
In theory, source removal and replacement should be the most effective
measure in reducing contaminant concentrations and human exposure.
Sources, however, must be correctly identified and low-/no-emission
replacements must be available for source removal to be effective. It is
important that removal and replacement costs are reasonable, particularly
when an indoor environment (IE) problem has low to moderate seriousness.
In some cases, materials that emit significant levels of HCHO (such as
particle board flooring, MDF or particle board workstation surfaces, pressed
wood cabinets) can be removed and replaced with materials that either do
not emit HCHO and or have low emission levels. Alternative materials
include softwood plywood and oriented-strand board.
Source removal associated with HCHO emissions from pressed wood
products has historically posed significant challenges. Among these are inter-
action effects associated with the presence of multiple HCHO sources. In
multiple source environments, it is common for a source with high emission
potential (dominant source) to suppress emissions from other sources.
Removal and replacement of lower-emission-potential sources (which may
be present at relatively high loading rates) without simultaneously removing
the dominant source typically fails to reduce HCHO levels to the degree
expected when emission potentials of individual sources are considered
singly. Other challenges involve mobile homes where interior and exterior
walls are fastened to particle board floor decking. In such cases, removal
and replacement is not practical. In office environments where pressed
wood-based furniture and workstations are the major source of HCHO,
removal and replacement with other materials would, in many cases, be
considered excessively costly.
In the case of office equipment, removal and replacement of wet process
photocopiers which have significant VOC emissions may be a desirable
mitigation measure. Removal of badly soiled carpeting and its replacement
with floor tile has been reported to result in a significant reduction in occu-
pant symptoms in Swedish schools.
Source removal has seen its most significant use in efforts to control or
prevent exposures to asbestos and lead. A further discussion of these is
included in the contaminant-specific source control section of this chapter.
B.
Source treatment and modification
Contaminant emissions from a limited number of sources can be reduced
by (1) the application of materials and coatings that serve as diffusion bar-
riers or contaminant scavengers, (2) exposure to gas-phase substances, and
(3) heat treatment.
