Surgical masks. Requirements and test methods (UNE-EN 14683: 2019 + AC).

The transmission of infectious agents can occur in several ways: air, direct contact, inoculation, ingestion, insect or other arthropod bites, animal bites, etc. The most frequent source of infection is the airway through secretions from the upper respiratory tract, such as those coming from the nose (nostrils and nasopharynx) and from the mouth (oral, pharynx, or other deeper airway locations). When a person speaks, coughs, sneezes, ..., he releases droplets (Wells´ droplet nuclei) from the secretions coming from the mucous membranes of the mentioned locations. The diameter of most of the droplets is between 0.5 µm and 12 µm, being especially the largest droplets that may contain microorganisms from the mucous membranes. The droplets can spread through the air to a location reaching an open surgical wound, sterile surgical instruments, or the mucous membranes of the airways, ocular conjunctiva, and even another individual´s own skin.

The main intended use of surgical masks is to protect the patient from infectious agents that may be emitted by healthcare personnel. In addition, in certain circumstances, they can also protect the user against splashes of potentially contaminated liquids, from a patient or another person in their environment. This means that surgical masks are used for patients or others to wear to reduce the risk of spreading infections, particularly in epidemic or pandemic situations.

Document UNE-EN 14683: 2019 + AC, specifies the construction, design, operating requirements and test methods of surgical masks intended to limit the transmission of infectious agents from medical personnel to patients during surgical procedures or in other medical settings. with similar requirements. A surgical mask constitutes is effective in reducing the emission of infectious agents from the nose and mouth by an asymptomatic carrier of an infectious agent or from a patient with clinical symptoms.

Surgical masks intended for use in operating rooms and others can be of three types. This standard describes the evaluations of two types of surgical masks (type I and type II) with their corresponding protection levels. At a minimum, Type I surgical masks are used for patients to reduce the risk of spread of infection, particularly in epidemic or pandemic situations. Type II masks are primarily intended for use by healthcare professionals in an operating room or other medical setting where the same conditions are required. The two types (I and II) differ according to their bacterial filtration efficiency. Type II is further subdivided depending on whether or not the mask is splash resistant (R: splash resistant). Type I efficacy has a bacterial filtration efficiency (BFE) of ≥ 95%, whereas Type II efficacy (BFE) is ≥ 98%. Type I are recommended only for use by patients or others to reduce the risk of the spread of infection in epidemic or pandemic situations and are not indicated for use by healthcare professionals in operating rooms or other medical settings.

The level of effectiveness offered by a surgical mask depends on factors such as the effectiveness of filtration, the quality of the material and the adaptability of the mask to the face of the person wearing it, remaining in contact with the nose, mouth and chin. There are different designs so this is important to achieve the desired result. The filtration capacity of the mask materials can vary depending on the elements that make it up. The adaptability of the masks varies considerably from those that are held in place by means of loops located on the back to attach to the ears, to those that use elastic fasteners around the head and a nose clip that can adapt to the nasal contour who wears the mask.

The surgical mask is generally made up of a layer that acts as a filter, which is placed, joined or molded between layers of fabric. The surgical mask must not disintegrate, break or tear during use. In selecting the filter and coating materials, attention should be paid to cleanliness. The masks can have different shapes and constructions, as well as additional features such as a face shield (to protect the wearer from splashes or droplets) with or without an anti-fog function, or a nasal bridge (to improve adaptability around the nose contour).

The conditions of this European standard are not applicable to masks intended exclusively for the personal protection of clinical personnel. For the protection of clinical staff it is recommended to follow the ISO 22609: 2004 standard (Protective clothing against infectious agents. Medical masks. Test method of resistance to penetration of synthetic blood. Fixed volume, projected horizontally / Clothing for protection against infectious agents -medical phase masks- test methods for resistance against penetration by synthetic blood. Fixed volume, horizonthally projected), or ASTM F1670 / F1670M (Standard Test Method for the resistance of materials used in protective clothing to assess the penetration of synthetic blood / Standard test method for resistance of materials used in protective clothing to penetration by synthetic blood). The ASTM F1670 / F1670M standard is accredited by ENAC in our laboratory.

All tests must be carried out using finished products or samples cut from finished products. For thick and rigid masks such as rigid or cup-shaped duckbill masks, this test method may not be suitable as complete fit cannot be achieved in the cascade impactor used in the evaluation of Bacterial Filtration Efficacy (BFE). In these cases, another valid equivalent method must be used to determine the BFE.When a mask consists of two or more areas with different characteristics or different layer composition, each part or area must be tested individually. The part or area whose characteristics offer the lowest level of performance should determine the BFE value of the complete mask.

In vitro Determination of Bacterial Filtration Efficiency (BFE)

In this test, a sample of the mask material (or more if the mask consists of areas of different structure) is fixed in a six-stage cascade impactor. The cascade impactor is located between an aerosolization chamber in which an aerosol containing the Staphylococcus aureus bacteria is generated and a vacuum-generating sucker. In this way the aerosol with the bacteria is passed through the mask material. The bacterial filtration efficiency (BFE) of the mask is given by the number of colony forming units (CFUs) that pass through the material of the surgical mask, expressed as a percentage of the number of CFUs present in the inoculation spray.

There are different parameters that must be taken into account in the evaluation system: 1) Nebulizer capable of producing particles whose average size is (3.0 ± 0.3) µm when coupled with the cascade impactor; 2) Staphylococcus aureus bacterial inoculum with 1.7 x 103 to 3.0 x 103 CFU per test; 3) Aerosol chamber 600 mm long and 80 mm in diameter; 4) Six stage cascade impactor; 5) Flowmeters to measure a flow rate of 28.3 L/min; 5) Manometer capable of measuring a pressure of 35 kPa with an accuracy of ± 1 kPa; 6) Erlenmeyer flasks, 250 mL and 500 mL capacity to retain particles that have passed through the mask; 7) Peristaltic vacuum pump, capable of establishing a flow rate of 0.01 mL/min. 8) Vacuum pump, capable of maintaining a flow of 57 L/min.

To perform the test, the test samples must be cut from full face masks. A full mask can be used in place of a cut sample, provided that by removing the ends, the mask can be arranged flattened and all its layers incorporated. In the case of being folded masks, the mask must be unfolded to test a surface as flat as possible. Each sample should be 100 mm x 100 mm in size and should include all layers of the mask in the order in which they are placed on the entire mask. The test must be carried out at least five times (5 samples), but this number can be greater and must be increased if necessary to allow obtaining an acceptable quality level (AQL: Acceptable Quality Level) of 4%. All samples tested should be taken from representative areas to incorporate all possible variations in filtration depending on the area of ​​construction. Unless otherwise indicated, the assay should be performed with the interior of the surgical mask in contact with the bacterial inoculation material. Each test sample should be conditioned at (21 ± 5)°C and (85 ± 5)% RH for a minimum of 4 hours to reach equilibrium with the atmosphere prior to testing.

Microbial cleaning (biological load)

The biological load of a surgical mask is evaluated according to EN ISO 11737-1: 2018 and must be ≤ 30 CFU/g. The same procedure of the cited standard is also indicated in this standard.

The number of masks to be evaluated is a minimum of 5 from the same batch. In the test report, the total biological load per individual mask and the total biological load per gram based on the mask weight are indicated.

The samples of the mask used for the tests should be chosen from their original primary packaging (dispenser box or equivalent), as they are offered to the end user, choosing 5 samples from the same batch, taking the upper sample, the lower sample and 3 randomly selected face masks. If the mask contains a visor or other accessories, these should be included in the tests.

In the microbial cleaning test, the entire mask must be weighed to include it in a volume of liquid culture medium in which it is kept under agitation to extract the microorganisms that it may contain. The liquid medium is subjected to duplicate filtration to retain the microorganisms in the respective filters and then the filter is cultivated, both in culture media for bacteria and fungi. From the cultures, the counts in CFU of the total biological load of each mask are expressed.

Testing cost

• Basic price for bacterial filtration efficiency (BFE): consult to ivami@ivami.com.

• Basic price for determining the total biological load (bacteria and fungi): Consult to ivami@ivami.com.

Basic price

It is applied for each sample submitted to the test/s with 5 units evaluated per test.

Form with the characteristics of the product and material necessary to carry out the tests

The applicant must provide a complete container for each requested test containing the product (masks) under evaluation, so that the laboratory takes the 5 units necessary to perform each requested test, following the selection system recommended by the standard. At the same time it will provide the completed form with all the characteristics that you want to appear in the report.

Results delivery

It will be approximately 20 to 30 working days from the reception in our laboratory of the sample and the form with the requested conditions for the test. If we have the results before we will notify you. The time is based on the tests that are being carried out at the time of receiving the samples.