Civil Engineering Reference
In-Depth Information
700
Formaldehyde
Acetaldehyde
Acetone
Propanal
Butanal
Benzaldehyde
Hexanal
600
500
400
300
200
100
0
Super plasticizer
Component
Defoamer
Cohesion
agent
Paint
Resin
15.3
Formation of carbonyl compounds as secondary emissions
during the irradiation of paint constituents mixed with anatase TiO
2
.
15.4.3 Possible solutions to diminish the accumulation of
by-products during photocatalysis
Indoor environments are characterized by the coexistence of multiple emis-
sion sources responsible for overall indoor air pollution. Formaldehyde is
a well-known and ubiquitous indoor pollutant emitted from a wide variety
of indoor sources, such as household products, furniture or smoke. Similarly,
NO
2
is commonly found in indoor environments and originates mainly from
combustion and gas appliances. Reported indoor concentrations of formal-
dehyde and NO
2
in dwellings range from 15 to 30
μ
g m
−3
and from 15 to
50
g m
−3
, respectively (WHO, 2010).
The formation of NO
2
and/or carbonyl compounds as by-products is an
undesirable effect, contributing to the chemical load in indoor environ-
ments, and should therefore be eliminated or minimized as far as possible,
as they might contribute as a relevant additional source which might exceed
the guideline values.
Two different approaches are commonly used to improve indoor air
quality and avoid the accumulation of indoor pollutants: they are source
control and eventual substitution of the emission sources, and increasing
the ventilation.
Studies carried out on the formation of by-products during the photo-
catalytic degradation of both inorganic and organic pollutants indicate that
a relatively large amount of by-products is accumulated, even under the
realistic conditions of an air exchange rate of 0.5 h
−1
and typical indoor
concentration levels of the various pollutants. In this sense, experiments
carried out on exposure chambers with a synthetic atmosphere containing
50
μ
μ
g m
−3
NO, in order to simulate an indoor environment, resulted in the
Search WWH ::
Custom Search