What type of breathing apparatus provides protection only for specific, known hazards?

The type of breathing apparatus that provides protection specifically for known hazards is the air-purifying respirator. This device is designed to filter out specific contaminants from the air, such as certain gases, vapors, or particulate matter, depending on the filters used. Air-purifying respirators are most effective when the hazards are well understood and can be matched with the appropriate filter, such as in environments where the contaminant types and concentrations are known.

In situations where there are unknown hazards or a potential lack of oxygen, relying solely on air-purifying respirators would be inappropriate, as they do not supply breathable air but rather clean the air that is already present. Self-contained breathing apparatus and powered air-purifying respirators are designed for different scenarios, focusing on broader protection, including environments that require secure, independent air supplies or enhanced filtration capabilities along with powered airflow.