ASTM G-124 seeks to evaluate combustion characteristics of metals in high-purity (>99%) oxygen atmospheres. ASTM G-124 provides the following equation to determine the minimum number of purges required to reach this level of purity in a test chamber: n = -4/log 10 (P a /P h ), where "n" is the total number of purge cycles required, P h is the absolute pressure used for the purge on each cycle and P a is the atmospheric pressure or the vent pressure. The origin of this equation is not known and

more »

... as been the source of frequent questions as to its accuracy and reliability. This paper shows the derivation of the G-124 purge equation, and experimentally explores the equation to determine if it accurately predicts the number of cycles required.