National Institute for Occupational Safety and Health

“ Zero the balance before each weighing. b. Handle the filter with forceps. Pass the filter over an antistatic radiation source. Repeat this step if filter does not release easily from the forceps or if filter attracts balance pan. Static electricity can cause erroneous weight readings. Assemble the filters in the filter cassettes and close firmly so that leakage around the filter will not occur. Place a plug in each opening of the filter cassette. Place a cellulose shrink band around the filter cassette, allow to dry, and mark with the same number as the backup pad.
SAMPLING: 5. ”

“ PREPARATION OF FILTERS BEFORE SAMPLING: 1. 2. 3.
4.
Equilibrate the filters in an environmentally controlled weighing area or chamber for at least 2 h. NOTE: An environmentally controlled chamber is desirable, but not required. Number the backup pads with a ballpoint pen and place them, numbered side down, in filter cassette bottom sections. Weigh the filters in an environmentally controlled area or chamber. Record the filter tare weights, W 1, (mg) . a. ”

“ The working range is 0.5 to 10 mg/m 3 for a 200-L air sample. This method is not applicable for the determination of "cyclohexane-solubles" [3] . This analysis is simple but the method is nonspecific. Information on any o ther particulate materials present should be assessed. The method may be extended to higher air concentrations (e.g., nuisanc e dust levels) by collecting a smaller sample volume [4] . ”