Abstract: A method of testing air for measuring the chromate and chromic acid aerosols therein, comprises, passing the air through a testing tube after each end of the tube has been broken to cause the particles in the air to become entrained on a filter in the tube and, thereafter, breaking an ampoule of sulfuric acid in the tube so that it flows through the filter and dissolves the entrained particles and brings them into contact with a filling material which is also arranged in the tube and which produces a reaction with the particles of chromate and chromic acid which are deposited on the filter. The reaction produces a violet dye, the intensity of the discoloration being directly proportional to the mass of the deposited chromate or chromic acid.