Respirators are rated based on which two sets of criteria?

The rating of respirators is primarily determined by their filtering capability and resistance to oil. Filtering capability refers to the respirator's efficiency in removing harmful particles from the inhaled air, which is crucial for ensuring that the wearer is adequately protected in environments with contaminants. Different filters are rated based on their ability to capture specific types and sizes of particles, leading to classifications like N95, P100, and R95, each indicating the level of filtration and resistance.

Resistance to oil is particularly relevant for certain types of respirators designed for environments that may contain oil-based aerosols. For instance, respirators with the "P" designation can be used in environments where oils are present, making them more versatile. These ratings help users select the appropriate respirator based on the specific hazards present in their work environment, ensuring their safety and compliance with health regulations.

The other criteria mentioned, such as breathability, comfort, and durability, are important for usability, but they do not directly relate to how respirators are rated in terms of their protective performance and suitability for different exposure scenarios.