1.1 This practice covers procedures for adjusting the size ranges of an airborne discrete particle counter (DPC) to match size/concentration data from a reference DPC that has been calibrated for counting and sizing accuracy in accordance with Practice F 328 and is kept in good working order. The practice is applied in situations where time, capabilities, or both, required for carrying out procedures in Practice F 328 are not available. It is particularly useful where more than one DPC may be required to observe an environment where the particulate material being counted and sized is different in composition from the precision spherical particulate materials used for calibration in Practice F 328 and/or all of the DPCs in use are not similar in optical or electronic design. 1.2 Procedures covered here include those to measure sampled and observed air volume or flow rate, zero count level, particle sizing and counting accuracy, particle sizing resolution, particle counting efficiency, and particle concentration limit.