By Trevor Horne

Understanding The Different Levels Of Medical Masks

Considering the current times – the age of the coronavirus – it is more important than ever that quality face masks be used and the different levels of facemasks be understood. Fortunately, supplies of face masks seem to have improved, but they were hard to find for a while. Is the best facemask necessarily the most expensive? Is it better to buy in large quantities? For your particular application, what's the right grade of medical masks?

The American Society for Testing and Materials (ASTM) is generally responsible for grading American-made surgical facemasks. They publish technical standards for systems, materials, products, and the like. Currently, worldwide, there are approximately 12,000 ASTM standards.

However, not all products are graded by ASTM! Whether your workplace is in research, pathology, or surgery, to minimize your risk, you need the appropriate level of protection. To be comfortable with that level of protection, make sure you buy your medical masks from a reputable manufacturer and that they are ASTM graded if manufactured in America – or at least validated and meet the requirements of Healthcare Workers in North America if manufactured elsewhere (such as Canada).

Mask Levels

Masks are rated numerically, as per the test results, on the material’s barrier performance. The following are mask levels:

  • Level III – Use in the case of high risk of spray, fluids, and/or aerosol spray. Maximum barrier protection.
  • Level II – Use for low to moderate level spray, aerosols, and/or fluids. Moderate barrier protection.
  • Level I – For general use only. Not used for spray, aerosols, or fluids. Low barrier protection.

Performance Criteria for Mask Testing

You may wonder what kind of criteria medical masks have to meet to pass a specific test or performance level. Key performance criteria for mask testing are as follows:

  • Flammability
  • Breathability
  • Fluid resistance
  • Particulate filtration efficiency
  • Bacterial filtration efficiency

A mask grades higher the more resistance it offers to any of the criteria listed above. It offers a higher protection rate. Though better suited for working with chemicals or surgery, higher protection masks will not protect against vapors. A respirator is needed in the case of vapors.


A mask is exposed to a flame. The time it takes for that flame to travel 5 inches determines its flammability.


A controlled airflow is driven through a mask. The resistance of the facemask to that airflow tests the breathability. A higher level of comfort for the user is offered by lower breathing resistance.

Fluid Resistance

At high velocity, a mask is exposed to 2 mL of synthetic blood. Visual evidence will determine the testing and evaluation of penetration resistance. This is a pass or fail test.

Particulate Filtration Efficiency

These tests and measurements refer to mask filtration of particles in excess of 1 micron.

Bacterial Filtration Efficiency

As with the above-stated test, mask filtration of particles is tested and measured here but for particles larger than three microns.

Looking for Medical Masks?

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