Chemistry of Phosphorus during Hazardous Production Materials System Maintenance and Implications for Gas Detection The maintenance of Hazardous Production Materials (HPM) systems frequently involves the handling of phosphorus deposits, which undergo complex chemical interactions with ambient air. These reactions are influenced by factors such as the specific allotrope of phosphorus and the presence of water vapor, both of which can significantly alter the composition of the resultant reaction products. Among these products, phosphine (PH₃) is of particular concern due to its high toxicity, necessitating stringent monitoring protocols.This presentation aims to address several key questions: Are conventional methods for phosphine detection adequately suited for HPM maintenance environments? In cases where phosphine is detected, can the signal be reliably attributed to phosphine generation, or could it arise from false positives due to the presence of other reaction products? Additionally, if false positives are a prevalent issue, what alternative detection strategies or mitigation measures can be implemented to more effectively monitor and control phosphine risks during HPM system maintenance?