§ 86.112-91 Weighing chamber (or room) and microgram balance specifications.

(a) Ambient conditions—(1) Temperature. The temperature of the chamber in which the particulate filters are conditioned and weighed shall be maintained to within ±10 °F (6 °C) of a set point between 68 °F (20 °C) and 86 °F (30 °C) during all filter conditioning and filter weighing. A continuous recording of the temperature is required.

(2) Humidity. The relative humidity of the chamber in which the particulate filters are conditioned and weighed shall be maintained to within ±10 percent of a set point between 30 and 70 percent during all filter conditioning and filter weighing. A continuous recording of the temperature is required.