A traditional Near Field-Far Field approach-based model and a spreadsheet workbook to manage Oxygen Deficiency Hazard

Oxygen Deficiency Hazard (ODH) poses a serious occupational risk, and represents a frequent cause of incidents, accidents, and fatalities, mostly in confined spaces and laboratories. Besides these working environments, there is a large spectrum of industries that need to manage the asphyxiation risk caused by extensive inert gas uses. In such a context, mathematical models represent a valuable tool for characterising exposure profiles under varying conditions and evaluating several exposure scenarios, prospectively or retrospectively, for new processes and/or non-routine events. To this end, the objectives of this paper are to: (1) define a traditional Near Field-Far Field (NF-FF) model to estimate the indoor oxygen (O2) concentration percent by volume and partial pressure, and (2) develop a spreadsheet workbook, called ODHMOD, for supporting occupational hygienists, safety and health practitioners, and risk assessors during ODH assessments. Both the NF-FF model and ODHMOD employ data and information usually available in companies, and predict the O2 levels time trends in working environments where inert gas releases can occur, and forced and natural ventilation can move airflows inside and/or outside. The mathematical model and its implementation in Microsoft® Excel are described, with an example of its application in a possible industrial scenario.