Which rating system is used for nonpowered air-purifying respirators to denote efficiency?

The correct choice for the rating system used for nonpowered air-purifying respirators to denote efficiency is the N, R, or P rating system. This system categorizes respirators based on their ability to filter airborne contaminants and provides guidance on their use in different environments.

• The "N" rating indicates that a respirator is not resistant to oil, and it is suitable for use in environments that do not contain any oily aerosols.
• The "R" rating means that the respirator is resistant to oil, which allows for a little more versatility in workplaces where some oil aerosols may be present.

• The "P" rating signifies that the respirator provides a high level of protection and is suitable for environments that contain oil or other particulate contaminants.

This rating system is important because it helps you choose the right respirator based on the specific conditions you may encounter at a job site, ensuring both safety and compliance with health regulations.

The other rating systems mentioned do not apply to nonpowered air-purifying respirators in the same manner and are not recognized for efficiency classification in this context.