American Society for Testing and Materials defines more than 12,500 international standards for safety and quality cross a wide variety of industries and services. Healthcare organizations globally adopt ASTM recommendations to implement best practices.

For masks, ASTM sets three levels of barrier protection:

1. Level 1: low barrier protection: general use for short procedures and exams that don’t involve aerosols, spray or fluids.
2. Level 2: moderate barrier protection: for low to moderate levels of aerosols, spray and/or fluids.
3. Level 3: maximum barrier protection: for heavy levels of aerosols, spray and/or fluids.

To determine if a mask is Level 1, 2 or 3, ASTM evaluates several characteristics, including bacterial filtration efficiency, sub-micron particulate filtration, differential pressure and flame spread. The greatest difference between the three levels is in the mask’s resistance to penetration by synthetic blood. The minimum resistance pressure in a Level 3 mask is double that of a Level 1 mask.

A surgical mask is a loose-fitting, disposable device that creates a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment. They are used for performing patient procedures, or when patients are in isolation to protect them from potential contaminants. Surgical masks are used to protect both patients and staff from the transfer of respiratory secretions, fluids or other debris. Surgical masks are used for generally "respiratory etiquette" to prevent clinicians, patients and visitors from spreading germs by talking, coughing, or sneezing. Surgical masks have ear loops for quick donning, and since they do not slide on the hair, they can be worn without a surgical cap.

An N95 respirator is a respiratory protective device designed to achieve a very close facial fit and very efficient filtration of airborne particles. Note that the edges of the respirator are designed to form a seal around the nose and mouth. Surgical N95 Respirators are commonly used in healthcare settings and are a subset of N95 Filtering Face-piece Respirators (FFRs), often referred to as N95s.