Predictive models to assess Oxygen Deficiency Hazard (ODH): a systematic review

Oxygen Deficiency Hazard (ODH) may expose workers to asphyxiation risk. ODH assessment is often carried out only for highly risky working environments and through monitoring. We conducted a systematic review of the literature to identify predictive models that estimate indoor oxygen level and assess ODH in any working environment. The implementation of these models may be of help to the employer for the adoption of preventive and/or protective measures in order to improve workers' health and safety. We focused on models dealing with ODH assessment caused by inert gas releases. Inert gases are usually used in confined spaces and laboratories, and may cause asphyxiation without any preliminary physiological sign. The systematic review returned sixteen models for estimating oxygen concentration, oxygen partial pressure and/or ODH Classes. We critically analysed and compared predictive models through a framework of qualification indicators regarding indoor and outdoor parameters, ventilation aspects, causes and releases, and outputs. The analysis pointed out the weaknesses of the existing models that need to be addressed by future research, in particular related to the estimation of indoor oxygen level in time and in space, and the consideration of accidental releases and of HVAC systems reliability. The framework is also intended to support the selection of the most suitable model for the ODH assessment in a specific working environment.