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Place the calcium chloride desiccant container on the calibrated electronic gram scale. (Scale kits from Vaprecision have calibration weights and easy-to-follow instructions.)  Starting weight of the tape-sealed dish unit, is about 30 to 31 grams. A slight amount of variability is normal. It is important that the same scale be used for weighing the test before and after exposure. Write down the start weight, the date and the time, on the dish label, as well as on the enclosed instruction booklet.