(a) Application. Use a balance to weigh net PM on a sample medium for laboratory testing.
(b) Component requirements. We recommend that you use a balance that meets the specifications in Table 1 of Sec. 1065.205. Note that your balance-based system must meet the linearity verification in Sec. 1065.307. If the balance uses internal calibration weights for routine spanning and the weights do not meet the specifications in Sec. 1065.790, the weights must be verified independently with external calibration weights meeting the requirements of Sec. 1065.790. While you may also use an inertial balance to measure PM, as described in Sec. 1065.295, use a reference procedure based on a gravimetric balance for comparison with any proposed alternate measurement procedure under Sec. 1065.10.
(c) Pan design. We recommend that you use a balance pan designed to minimize corner loading of the balance, as follows:
(1) Use a pan that centers the PM sample media (such as a filter) on the weighing pan. For example, use a pan in the shape of a cross that has upswept tips that center the PM sample media on the pan.
(2) Use a pan that positions the PM sample as low as possible.
(d) Balance configuration. Configure the balance for optimum settling time and stability at your location. [73 FR 37300, June 30, 2008, as amended at 75 FR 68462, Nov. 8, 2010]