What is a critical air quality consideration for an Air Purifying Respirator?

A critical air quality consideration for an Air Purifying Respirator is that oxygen levels must be between 19.5% and 22%. This range is essential because air purifying respirators are designed to filter out contaminants from the air, but they do not provide oxygen. If the oxygen concentration in the ambient air falls below 19.5%, it can become hazardous, leading to potential asphyxiation or impaired cognitive function for the user. On the upper end, concentrations above 22% may also pose hazards, such as increased fire risk. Therefore, ensuring oxygen levels remain within this specified range is vital for the safe use of air purifying respirators.