A predictive model for estimating the indoor oxygen level and assessing Oxygen Deficiency Hazard (ODH)

A Near Field–Far Field model for assessing Oxygen Deficiency Hazard

“…n O2,air,inNF t-δt,t = b air,inNF n air t-δt,t C O2,FF t-δt (28) n O2,air,outNF t-δt,t = b air,outNF n air t-δt,t C O2,NF t-δt 293.3.3.2 Far Field Thanks to the equations reported in Table 4 and already addressed in Stefana et al (2016), the risk assessor can estimate the moles of forced ventilation airflow (supply and return air) in terms of oxygen, each pure inert gas, and each impurity.…”

“…In this case, they may exploit tables available in the literature that show the different symptoms and physiological effects at different concentrations by volume. An overview of this information is provided in Stefana et al (2016).…”

“…3, the NF composition can change because of inert gases released voluntarily and/or accidentally, the interzonal airflow, and the air that has to move from the FF to the NF, or vice versa, for assuring a limit value for the oxygen concentration in the NF. In order to estimate the moles of oxygen, of main pure inert gas, of each other pure inert gas, and of each other impurity related to voluntary and/or accidental releases of inert gases, we can exploit equations reported in Table 3, as already addressed in Stefana et al (2016).…”

“…The moles introduced into or drawn from the working environment with natural ventilation can be calculated adapting the formulas reported in Stefana et al (2016) and considering as internal conditions the ones of the FF. We have supposed that natural ventilation, infiltration, and exfiltration are driven only by pressure difference inside and outside the working environment.…”

“… possibility to set initial indoor air composition;  possibility to set indoor temperature in time;  possibility to set initial total pressure of indoor air;  possibility to set total pressure of indoor air in space and/or in time;  possibility to consider working environment, and plant layout or plant logic diagram;  possibility to set outdoor oxygen concentration in space and/or in time;  possibility to set outdoor air composition in space and/or in time;  possibility to set natural ventilation and infiltration airflow rate in time;  possibility to consider reliability of Heating, Ventilation, Air Conditioning, and Refrigeration (HVAC-R) systems and/or plant components;  presence of examples of reliability values of plant components;  possibility to consider more failures simultaneously;  possibility to evaluate releases of more substances and/or mixtures simultaneously;  possibility to model substances and mixtures like real gases;  possibility to set composition of release mixtures in time;  possibility to consider release flow rate in space;  possibility to set pressure of release flow rate in space. The seventeenth model by Stefana et al (2016) seeks to overcome some of these weaknesses, such as the possibility to set initial indoor air composition, consider reliability of HVAC-R systems, and evaluate releases of more substances and/or mixtures simultaneously. However, this last model does not have the possibility to estimate indoor oxygen level in space.…”