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Section 2.2.5 <br />Revision No. 0 <br />Date May 1, 1977 <br />• Page 2 of 3 ~ •. <br />chamber, employing a saturated chemical solution that will <br />result in a relative humidity of less than 50 percent at a <br />temperature of approximately 20 to 25°C is recommended in <br />lieu of a controlled temperature/humidity weighing room. <br />An air conditioned room may be used for equilibration. <br />A relative humidity less than 50 percent and constant within <br />+5 percent, and an air temperature constant within +3°C must <br />be maintained in the room while filters are equilibrating. <br />A conveniently working relative h~.unidity is 40 percent. A <br />hygrometer is maintained in the room and the relative humidity <br />must be checked daily. <br />Record hygrometer readi.^.gs and wry equilibration chamber <br />malfunction, discrepancies, or maintenance in the laboratory <br />data log, Figure 3.1. <br />5.3 Gravimetric Analysis <br />• Perform a balance check as specified in Section 2.1. <br />Weigh exposed filters to the nearest milligram on the analytical <br />balance within 30 seconds after removal from the equilibration <br />chamber. The weighing location should be in the conditioning <br />environment if practicable, otherwise the analytical balance <br />should be as close as possible to the conditioning chamber <br />in a location that is relatively free of air currents and <br />is at or near the temperature of the chamber. Record the <br />weight in the laboratory data log and on the hi vol field <br />data sheet. <br />u <br />