Infective agents can be transmitted during surgical procedures in operating theatres and other medical settings in several ways. One of the important sources are the noses and mouths of the surgical team. When breathing, speaking, coughing or sneezing, a person releases smaller or larger amounts of droplets of secretions from the mucous membranes in the mouth and nose. Those droplets quickly evaporate and leave nuclei suspended in the air. Nuclei can subsequently spread through the air to a susceptible site such as an open operating wound or sterile equipment, or can be inhaled if dimensions are very small.

A surgical mask is a medical device covering the mouth, nose and chin ensuring a barrier that limits the transition of an infective agent between the hospital staff and the patient. It was originally developed to contain and filter large droplets of microorganisms expelled from the mouth and nasopharynx of healthcare workers during surgery, thereby providing protection for the patient.

The main objective of wearing a surgical mask is to protect the direct environment of the wearer from contamination.

Manufacturers have to characterise and classify their surgical face masks in type I or II for the European market and in level 1, 2 ot 3 for the American one.

Evaluation of surgical masks in Europe：

The FDA (US Food and Drug Administration) is the organism that regulates medical devices on the USA market. Surgical masks are considered medical devices class 2.

The FDA has drafted standards to which manufacturers have to comply in order to receive a licence to sell the products on the market. The same standards apply to surgical masks, procedures, isolation, dental interventions and laser treatments.

The FDA strongly recommends that the manufacturer clearly indicates the use of the product on the package.

The masks are submitted to the same tests as the ones described in the European standard EN14683, except that the FDA also prescribes the measurement of filtration efficiency regaring inert particles (latex) and fire tests.

The US standard ASTM F2100-11 Standard specification for performance of material used in medical face masks describes the tests and requirements with which the materials have to comply that are used to produce the masks. Several tests are not run on the final product, but on the different materials have to be tested together in the way they will be used in the final mask.

The performances of the materials composing the mask are evaluated by six tests :

• Bacterial fitlration efficiency

• Differential pressure

• Sub-micron particulate filtration efficiency at 0.1micron, %

• Resistance to penetration by synthetic blood

•  Minimum pressure in mm Hg for pass result

• Flame spread

According to the results, the masks are classified in three levels.

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