Document M1zevyOpQN5NxdEaavKBqQvy

Air Hygiene Foundation, 4400 ^ifth Avenue, Pittsburgh, Pa. February 24, 1939. NOTE TO MEMBERS: Enclosed is another bulletin in the seriejs prepared by the Preventive Engineering Committee of Air Hygiene Foundation. The new bulletin deals with "Routine Sampling for Control ok Atmospheric Impuritios" and gives methods for determining some 40 substances more or less commonly found in industrial atmospheres. Extra copies, in addition to the regular membership allotment, arc available at fifty cents each. H. B. Mellcr Managing Director 004358 [1 PLAINTIFF'S I . (EKHIB1T