What is a key characteristic of atmosphere-supplying respirators?

Atmosphere-supplying respirators are specifically designed to provide breathable air from an external source, such as compressed air tanks or other air supply systems. This characteristic is crucial in environments where the air may be contaminated or lacking in oxygen. By supplying air directly from a safe source, these respirators protect the user from inhaling hazardous substances present in the atmosphere, ensuring their safety while performing tasks in potentially dangerous environments.

The other options describe features of different types of respiratory protection but do not apply to atmosphere-supplying respirators. For example, filtering harmful gases is a function of air-purifying respirators, which use filters to remove contaminants from the air before inhalation. The fact that they are reusable may apply to some types of respirators, but it is not a defining characteristic of atmosphere-supplying respirators specifically. Additionally, the need for testing is generally a requirement for the safe use of all types of respirators, ensuring they are functioning properly before use.