Guidance for transparent medical mask technical specifications: Other requirements

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Overall design

Transparent medical masks will generally include a transparent area (made of plastic). The wearer’s mouth and parts of the face are visible to people who communicate by reading lips or have other speech and/or hearing-impairments.

This transparent area may be attached to or surrounded by a filter area or a flexible element, such as a foam strip. This helps the mask fit the face.

The medical masks must:

Transparent medical masks intended for specific uses (such as speech and language assessments) should:

Transparent medical masks may have different shapes and constructions. They may also have additional features such as a:

The filter area and seating element (a flexible element like a foam strip, which seats the mask to the face) must enable the wearer to breathe and wear the mask comfortably.

Like all masks and respirators, transparent masks should not contain any valves or air holes, which may release contaminated air. These are not recommended for use during the pandemic.

There may be other design requirements important to specific wearers, which are not dealt with in this specification.

Packaging and labelling

Transparent medical masks complying with this guidance must:

Non–medical transparent face coverings

Transparent medical masks and transparent face coverings/non-medical masks are different. Transparent medical masks help prevent the spread of viral particles and meet all the requirements for medical masks. Transparent non-medical masks provide source control only and facilitate communication but they are generally not as effective when it comes to filtration or fluid resistance.

Information on the label indicates the properties of the product and any performance claims. The label should contain the following elements:

Materials used to make the masks should be:

Those materials that come into direct contact with the skin must also be latex-free.

The composition of the materials used to make the mask must be indicated in the labelling.

Biocompatibility

The parts of the transparent medical mask that come into direct contact with the skin, nose and mouth must meet EN 14683 or ASTM F2100 standards.

Materials should be also be non-cytotoxic, non-sensitizing and non-allergenic. Thus, they should meet ISO 10993-5 (cytotoxicity) and ISO 10993-10 (skin sensitization and hypersensitivity) standards. 

Evidence that the materials used in the mask are biocompatible should be available upon request.

Filtration efficiency

The filtration efficiency of the transparent medical mask should be measured on the entire device. Each test method will need to be adapted as only a portion of the material is tested in each. Depending on the standard selected, filtration efficiency may be assessed through a particle filtration efficiency (PFE) test and/or a bacterial filtration efficiency (BFE) test. ASTM F2100 requires both PFE and BFE, while EN 14683 only requires BFE.

For PFE, the PFE minimum requirement according to ASTM F2100 is ≥95%.

For BFE, the minimum BFE is ≥98% (if using EN 14683, Type IIR) or ≥95% (if using ASTM F2100, Level 1).

It may not be possible to test the non-filtering component (transparent window area) to Annex B of BS EN 14683: 2019 or ASTM F2101. However, when tested for resistance to wet bacterial penetration, the non-filtering component should have a barrier index (IB) of 6.0. The test method is in BS EN ISO 22610:2006. Alternatively, an internationally recognized standard designed to demonstrate resistance to penetration of microorganisms (for example, ASTM F1671) may be used.

Breathability

The breathability tests used for medical masks in ASTM F2100 and EN 14683, Type IIR are not appropriate for transparent medical masks due to their unique design.

The complete mask should meet a airflow resistance testing similar to an FFR design. For more information, see the "Airflow resistance" section of our respirator guidance document.

Splash resistance

The filter area, transparent area and seams joining the 2 materials of the transparent medical mask should be able to keep splashes of liquid from penetrating. To do so, they must meet:

Microbial cleanliness (bioburden)

To meet EN 14683 standards, the bioburden of the transparent medical mask should be less than or equal to 30 cfu/g.

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