Physical form

The design of the surgical masks depends on the mode; usually, the masks are three-ply (three layers). This three-ply material is made up of a melt-blown polymer, most commonly polypropylene, placed between non-woven fabric.The melt-blown material acts as the filter that stops microbes from entering or exiting the mask.Pleats are commonly used to allow the user to expand the mask such that it covers the area from the nose to the chin. The masks are secured to the head with ear loops, head ties, or elastic straps.

Physical properties and quality

Performance of surgical masks is evaluated based on such parameters as filtration (mask capture of exhaled aerosols), exposure (transfer of aerosols from outside), mask airflow resistance (pressure difference during breathing, ΔP, also known as breathability), liquid penetration resistance, air and water vapor permeability, water repellency (for outer and inner surfaces).

Filtration and exposure is typically measured in bacterial filtration efficiency (BFE) using particles of size 3.0 μm. Particulate filtration efficiency (PFE) using particles of size 0.3 μm is only measured in China.