Environmental Engineering Reference
In-Depth Information
fumigation, a mobile home or other residential
environment is exposed to high NH
In conducting an NH
3
concentrations produced by a strong
ammonium hydroxide solution (28 to 30% NH
3
) placed in the closed building
at 80°F (26°C) for a period of 24 to 48 hours. Ammonia fumigations in real-
world evaluations have been observed to be effective in building environ-
ments with high HCHO concentrations (
3
0.20 ppmv), resulting in short-term
reductions of HCHO in the range of 58 to 75%, and longer-term reductions
on the order of 40 to 70%. They have been ineffective in building environ-
ments with relatively low HCHO concentrations (
≥
0.10 ppmv). Such con-
centrations appear to be the practical lower limit for HCHO reduction.
Ammonia fumigations were used by mobile home manufacturers and
others to mitigate health and odor complaints in new mobile homes. Their
primary advantage was that significant reductions in HCHO levels in build-
ings with large quantities of HCHO-emitting products could be achieved
at low cost and with minimum disturbance. Major disadvantages included
(1) the potential to cause stress corrosion and cracking of brass connections
on critical appliances such as gas stoves, water heaters, and furnaces, as
well as electrical connections; (2) the tendency to darken light oak cabinets;
(3) the inability to reduce HCHO levels below 0.10 ppmv on a permanent
basis; and (4) the persistence of irritating NH
≤
odors up to several weeks
3
after treatment.
3.
Building bakeout
Building bakeout is a source treatment procedure developed in the early to
mid-1980s to reduce VOC concentrations in new office buildings. It is based
on the principle that the normal decrease of VOC levels with time can be
accelerated by elevating building temperature for several days. Elevated
temperature causes increased VOC emissions because of increased vapor
pressures of residual solvents and monomers in finish coatings, caulks,
adhesives, etc. As a result of elevated temperature and increased ventilation
rate, bakeouts attempt to increase emission rates and reduce product emis-
sion potential.
The effectiveness of a building bakeout depends on several factors. These
include the maintenance of building temperature in the range of 86 to 95°F
(30 to 35°C), a bakeout duration of at least several days, an optimum venti-
lation rate, and initially high VOC concentrations. It is desirable to optimize
temperature, duration, and ventilation to achieve maximum VOC reduction.
Achieving optimal conditions is, however, difficult.
Complicating the task of conducting bakeouts are problems in attaining
the desired temperature range for a sufficient duration. Constraints include
the inability of some HVAC systems to reach desired temperatures without
supplemental heating, concerns that elevated temperatures may damage
building materials, and difficulties in providing sufficient ventilation to flush
emitted VOCs (so they are not readsorbed by building materials) from the
building environment.
