What type of respirator uses an external source for breathing air connected via a hose line?

The correct answer is a supplied-air respirator (SAR). This type of respirator is specifically designed to provide breathable air from an external source, typically connected via a hose. The use of an external air supply is crucial in environments where the oxygen concentration may be low or there are elevated levels of hazardous gases, ensuring the user has a continuous supply of safe air to breathe.

In contrast, an air-purifying respirator (APR) operates by filtering contaminants from the air, relying solely on the ambient air instead of an external supply. A powered air-purifying respirator (PAPR) also utilizes filters but adds a battery-powered fan to pull air through the filters. While it improves the flow of air to the user, it still depends on the ambient air quality rather than an external source. Open-circuit breathing apparatus typically refers to self-contained breathing apparatus (SCBA), which does not utilize a hose line for air supply but instead stores it in a tank worn by the firefighter.

The supplied-air respirator’s reliance on an external air source makes it an essential choice for operations in heavily contaminated environments, emphasizing the importance of continuous airflow to ensure safety and effectiveness in hazardous situations.