Environmental Engineering Reference
In-Depth Information
Particulate matter associated with both biomass cooking and coal use
has high PAH concentrations. In a study of 65 Indian households, benzo-
α
-
pyrene concentrations measured indoors averaged 3900 ng/m
, with a range
3
of 62 to 19,284 ng/m
, as compared with ambient concentrations of 230 and
3
107 to 410 ng/m
, respectively. Indoor concentrations of this potent carcin-
ogen can only be described as enormously high, while ambient concentra-
tions are significantly lower but nevertheless high with reference to accept-
able levels in developed countries.
As anticipated, significant concentrations of gas-phase substances are also
associated with biomass, coal, and other cooking fuels. In the Mozambique
studies, average indoor CO levels with wood and charcoal cooking were 42
and 37 ppmv, respectively. Elevated concentrations of CO in the range of 10
to 50 ppmv have been reported elsewhere. NO
3
levels in the range
of ~0.07 to 0.16 ppmv and ~0.06 to 0.10 ppmv, respectively, have been reported
in short-term (15-minute) measurements in Indian households using wood
or dung for cooking. High aldehyde levels in the range of 0.67 to 1.2 ppmv
have been reported in New Guinea households using biomass fuels.
and SO
2
2
B.
Gas and kerosene heating appliances
A variety of unvented heating devices that burn natural gas, propane, or
kerosene are used in the U.S. and other countries. These include gas and
kerosene space heaters, water heating systems (primarily in European coun-
tries), gas stoves and ovens, ventless gas fireplaces, and gas clothes dryers.
In each case, fuels are relatively clean-burning, i.e., they produce no visible
smoke. They have also been designed to burn with relatively higher efficien-
cies. As a consequence, they pose little or no risk of CO poisoning associated
with earlier appliances.
Unvented appliances used for home space heating have significant
advantages. Costs are low compared to heating systems that include rela-
tively expensive furnaces, ductwork, and flue/chimney systems. They can
also be used to spot-heat a residence, or, as in New South Wales (Australia),
classrooms. Heat is provided only where and when it is needed. Unvented
space heaters can also be used in environments where vented combustion
appliances may not make economic sense. These include vacation homes or
cabins, recreational vehicles, detached garage workshops, and even tents.
The use of kerosene heaters to spot-heat residences in the U.S. became
popular during the 1980s for the same reason that wood-burning appliances
were popular at that time, i.e., to reduce energy costs. Kerosene heaters
became popular only after low-CO-emitting devices became commercially
available. More than 10 million kerosene heaters were sold in the U.S. by 1985.
There are three basic types of kerosene heaters: radiant, convective, and
two-stage. They all utilize a cylindrical wick and operate at relatively high
combustion temperatures. In the radiant type, flames from the wick extend
up into a perforated baffle, which emits infrared energy (radiant heat). Such
heaters operate at lower temperatures than convection heaters, which trans-
