+ a III. Settled Dust on Gummed Paper Ao Collections Sheets of “Kum-Kleen™ gummed paper are supplied with a metal frame which will hold the paper by its own adhesive. This frame is placed on a box or suitable support next to the collecting tray and at about the same height with the gummed side up. The papers are changed every 24 hours whether precipitation occurs or not. The gummed face of the paper is then folded together and refolded to fit into a cellophane bag. The bag should be stapled to a data form containing the pertinent information. Collecting stations should send the paper, bag and data sheet to the specified laboratory, by mail, and if an appreciable saving of time would result, by air mail. IV. Airborne Dust Samples A. Collections Airborne dust samples are collected by drawing lkmown volumes of air through a paper filter. The pump furnished consists of a head for holding the filter, an AC-DC 115 volt motor-blower, and a gage for determining the air flow in cubic feet per minute. The pump should be protected from rain, and may be set up at an open window, or under a suitable shelter. The paper filter is mounted in the head with the rough, dark side out toward the entering air. The flow rate and date and how of starting should be noted on the data sheet. Since the flow rate may decrease as dust collects, the same data must be noted at the end of the run. The filter should be changed after every 24 hours. After removal, the filter is placed in a cellophane bag and the bag stapled toa data form containing the pertinent information. Logan ar Collecting stations should send the filter, bag and data sheet to the specified laboratory, by mail and if an appreciable saving of time would resuit, by air mail. “7] DO® ARCHIVES %