SCOPE AND EVALUATION OF ODOR COUNTERACTION AND MASKING *

The control of malodors in buildings and in the outside atmosphere has become an important aspect of maintaining an acceptable environment. Homes are faced with the generation of odors from many sources: kitchen, bathroom, smoking, and human and animal bodies. Hospitals have their own varieties of objectionable odors. Commercial buildings face the costly problem of replacing odorous air arising from large numbers of people by clean air that must be heated or cooled. Wherever people congregate odors may become a source of annoyance and irritation. Modern industry has created malodorous wastelands in many areas. Chemical plants, pulp and paper mills, steel and cement plants, and a variety of others pour out a constant stream of objectionable vapors. Odorants can be controlled in many cases by methods that either remove or destroy them. Sometimes, however, this is impossible. Consider a viscose plant spread out over two acres and emitting a mixture of hydrogen sulfide and carbon disulphide from more than 100 stacks. The cost of standard methods of odor control-adsorption, scrubbing, oxidationis prohibitive. Sewage plants and landfill operations similarly generate odorous vapors over wide areas, creating the same problems of control. Even where available methods can greatly reduce the concentration of odorous pollutants, results may be unsatisfactory, since the threshold concentration is extremely low for many odorants. Reduction in concentration up to 99% may be attainable at reasonable cost, but the destruction or removal of the final 1% can make the entire operation economically indefensible.