What distinguishes air-purifying respirators from atmosphere-supplying respirators?

Air-purifying respirators function by filtering out contaminants from the air, making them effective in environments where there is sufficient oxygen available. They work by using filters or cartridges to remove pollutants, allowing the wearer to breathe in clean air. However, their effectiveness is entirely dependent on the ambient air containing adequate levels of oxygen; without it, the user cannot safely use this type of respirator.

In contrast, atmosphere-supplying respirators operate differently. They provide the wearer with oxygen from a separate source, meaning that these respirators can be used in environments where oxygen levels may be low or where toxic gases are present. This difference in operation is critical because atmosphere-supplying respirators are designed to ensure that the wearer has a continuous supply of oxygen, regardless of the external air quality.

Thus, the correct distinction lies in the requirement for adequate oxygen availability when using air-purifying respirators, making them unsuitable for situations lacking sufficient breathable air.