Chemical analysis of atmospheric dust.

The chemical analysis of atmospheric dust is of interest to two major groups, namely—the workers in industrial hygiene and the workers in the air cleaning and ventilating industries. The industrial hygienists, who are concerned with the prevention of occupational diseases and the maintenance of the health of industrial workers on a high level, are mainly interested in the concentration of irritating dusts and allergy-producing dusts that would obviously affect the health or comfort of industrial workers. Their interest, as one would expect, is in atmospheric dust of small particle sizes (10 microns and smaller), and in gaseous substances which they believe to be the most important from a health standpoint. The air cleaning and ventilating industries face an additional aspect of the problem of air pollution. Their problem is to devise instruments for capturing and removing solid matter from a stream of air. This solid matter includes fibrous material, such as lint, particles of earth, carbon, sand, ash, pollen, etc. Probably the most abundant of these solid particles is carbon, which is the chief offender in soiling. The removing of this very undesirable property of soiling from the atmosphere is equally as important as removing materials that are harmful to health. The problem of control soiling is unique with the air cleaning and ventilating industries and has led to the development of considerable testing technology for its evaluation. Experience in these industries has shown that it is not only necessary to know the type of dust, its concentration and its chemical composition but also the percentage of soiling material present in the atmosphere, if a synthetic testing material is to be created which will give a true efficiency rating for a filter in the laboratory. Studies indicate that there are variations in opinions as to what per cent carbon black (Free Carbon) a synthetic testing material of this nature should contain. The results of the analysis presented in this paper should help to clarify this problem of testing filters under conditions similar to those of actual field operations. The chemical analysis of atmospheric dust is a complex problem. The complexity arises not only from the diversity of elements and compounds present in each local section of the earth’s crust but also from the various local artificial dust produced by man. Perhaps just as important as the concentration of these elements or compounds is the variety of physical forms these materials