1. Scope 1.1 This practice covers procedures for adjusting the size ranges of an automatic airborne particle counter (APC) to match size-concentration data from a reference APC that has been calibrated for counting and sizing accuracy in accordance with Practice F328 and is kept in good working order. The practice is applied in situations where time or capabilities, or both, required for carrying out procedures in Practice F328 are not available. It is particularly useful where more than one APC may be required to observe an environment with particulate material that differs in composition from the precision spherical particulate materials used for calibration in Practice F328.