Which of the following is a feature of airline respirators?

The feature of airline respirators involves a filtered air supply, which effectively provides clean, breathable air to the user. These respirators are designed to connect to an external air source, such as an air compressor, which delivers air through hoses to the person wearing the respirator. The air that is supplied is filtered to remove contaminants, ensuring that the worker is breathing in safe air while performing tasks, especially in environments with hazardous exposure.

This characteristic is crucial for applications in industries such as construction, chemical manufacturing, or any setting where airborne pollutants are present. Unlike self-contained breathing apparatuses, which use their own supply of air, airline respirators serve as a continuous source of filtered air, often allowing for extended use in situations where air quality may be compromised.

The other options pertain to features typically not associated with airline respirators. For example, self-contained air supplies are primarily found in different types of respiratory protection, while recyclable filters and built-in heaters do not correspond with standard features of airline respirators. This distinction is critical for understanding the appropriate application and functionality of each respiratory protection system.