There are numerous options for face masks that healthcare practitioners can choose from. These include basic medical masks, procedure and surgical face masks, anti-fog masks, fluid/splash resistant masks, and the list goes on. Masks are made to cover the nose and mouth with a blend of certain characteristics, comfort, filtration, breathability, and different levels of barrier protection (ASTM, 2020). The number of options available creates a confusing decision for healthcare professionals when choosing the right mask. Here we discuss the different characteristics of face masks for healthcare environments with regards to the requirements of Australian Standards for single-use face masks (AS 4381: 2015) to assist you in choosing the right mask for you and your practice.

What is ASTM?

ASTM International (American Society of Testing and Materials) is the organisation responsible for the global implementation of face mask standards and levels as well as developing and publishing technical standards for materials, products, systems, and services in healthcare (ASTM International, 2020). Today, over 12,500 ASTM standards are in use around the world for safety and quality across a wide variety of industries and services (ASTM, 2020). Healthcare organizations globally adopt ASTM recommendations to implement best practices. The Australian Standards committee (AS) develops their standards in accordance with global recommendations (ASTM, 2020)

Performance Metrics and Related Tests:

ASTM F2100-11 (Standard Specification for Performance of Materials Used in Medical Face Masks) offers a comprehensive set of tests for procedure and surgical face masks. These tests are essential to ensuring performance properties are validated to support claims and classify mask types.

Summary of face mask tests for ASTM2100-11:

• Bacterial Filtration Efficiency (BFE) – Test ASTM F2101

This test measures the percentage of bacteria larger than 3 microns filtered out by the mask.

• Resistance to penetration by synthetic blood – Test ASTM F1862 / F1862M – 17

This test evaluates the resistance of a face mask to penetration by a small volume (~2 mL) of synthetic blood at a high velocity (80 mmHg, 120 mmHg, or 160 mmHg).

• Differential Pressure ΔP (Breathability) – Test MIL-M-36954C

The Delta P test is performed to determine the breathability of masks by measuring the differential air pressure on either side of the test article using a manometer, at a constant flow rate of 8 L/min.

Factors to be considered when choosing an appropriate mask: ​

• Probability of exposure to blood and body substances​
• Type of body substance involved​
• Probable type and probable route of transmission of infectious agents
• The 5Fs of selecting the right mask (Maxwell & Boring, 2018).

AS 4381:2015 (Single-use face masks for use in health care)

The intended use for medical face masks is to protect the wearer from splashes or sprays during healthcare procedures, as well as keeping large splashes and sprays from the wearer from reaching the environment (CEC, 2020). The need for PPE should be based on the precautions required to protect against infectious agents based on the mode of transmission. In most situations where standard respiratory protection is needed, a single-use surgical mask (minimum level 2 barrier) is appropriate.

This standard sets out requirements for single-use face masks which are used in health care where it is necessary to keep cross-contamination between the health care worker and the patient to a minimum in Australia and New Zealand. According to AS 4381:2015, the applicable test for a single-use face mask is set out to be tested against 3 performance metrics (BFE, Delta P and Resistance to Penetration Blood).

(AS) 4381: 2015 SINGLE USE FACE MASKS – CHARACTERISTICS OF LEVEL1, LEVEL 2 AND LEVEL 3 FACE MASKS
Levels	Level 1	Level 2	Level 3
Characteristics	Low Barrier Protection	Moderate Barrier Protection	Maximum Barrier Protection
Definition	Low barrier protection. general use for short procedures and exams that do not involve aerosols, sprays, or fluids. Materials evaluated for resistance to penetration by synthetic blood at minimum velocity	Moderate barrier protection: for low to moderate levels of aerosols, sprays and/or fluids. Materials evaluated for resistance to penetration by synthetic blood at the middle velocity.	Maximum barrier protection: for heavy levels of aerosols, sprays and/or fluids. Materials evaluated for resistance to penetration by synthetic blood at the maximum velocity.
Application	For general purpose medical procedures, where the wearer is not at risk of blood or bodily fluid splash or to protect staff and/or patient from droplet exposure to microorganisms (e.g. patient with upper respiratory tract infection visits General Practitioners	For use in emergency departments, dentistry, changing dressings on small wounds or healing wounds where minimal blood droplet exposure may possibly occur (e.g. endoscopy procedures)	For all surgical procedures, major trauma first aid or in any area where the healthcare worker is at risk of blood or body fluid splash (e.g. orthopaedic, cardiovascular procedures).
Bacterial Filtration Efficiency (BFE) %	≥ 95%	≥ 98%	≥ 98%
Differential Pressure (Delta P) Differential Pressure mm H2O/cm2	<4.0	<5.0	<5.0
Resistance to penetration by synthetic blood, minimum pressure in mmHg for pass result	80 mmHg	120 mmHg	120 mmHg
Source: Standard AS 4381:2015

NOTE:
these characteristics are based on unworn masks and may differ or not meet performance expectations due to individual fit characteristics. All testing required to meet the standard has been aligned with equivalent test methods used in American Standards (ASTM F2100-11) and European Norms (EN14683)

Reference List:

1. Astm.org. 2020. Standards For Medical Face Masks And Protective Clothing | ASTM Standardization News. [online] Available at: <https://www.astm.org/standardization-news/?q=features/standards-medical-face-masks-and-protective-clothing-.html> [Accessed 18 June 2020].
2. ASTM 2020. Detailed Overview / ASTM Standardization [online] Available at: https://www.astm.org/ABOUT/full_overview.html [Accessed 18 June 2020].
3. ASTM F2100-19e1, Standard Specification for Performance of Materials Used in Medical Face Masks, ASTM International, West Conshohocken, PA, 2019, www.astm.org
4. ASTM F2299 / F2299M-03(2017), Standard Test Method for Determining the Initial Efficiency of Materials Used in Medical Face Masks to Penetration by Particulates Using Latex Spheres, ASTM International, West Conshohocken, PA, 2017, www.astm.org
5. ASTM F1862 / F1862M-17, Standard Test Method for Resistance of Medical Face Masks to Penetration by Synthetic Blood (Horizontal Projection of Fixed Volume at a Known Velocity), ASTM International, West Conshohocken, PA, 2017, www.astm.org
6. Maxwell, A. and Boring, T. L., 2020. Choosing The Right Mask. [online] Available at: <https://www.cardinalhealth.com.au/en_au/medical-products/infection-control/facial-protection/resources/choosing-the-right-mask.html> [Accessed 18 June 2020].
7. Cec.health.nsw.gov.au. 2020. [online] Available at: <http://cec.health.nsw.gov.au/__data/assets/pdf_file/0007/567394/Properties-of-different-types-of-masks.pdf> [Accessed 18 June 2020].
8. CG Davies et al, Ann R Coll Surg Engl 2007 89(8): 770–772; S Endo et al, Jour Hospital Infection 2007 (67) 1: 56–61; DC Berridge et al, Br J Surg 1993 80 (11): 1379-80.
9. Frazierinstrument.com. 2020. MIL-M-36954C. [online] Available at: <http://www.frazierinstrument.com/reference/standards/organizations/mil/abstract-mil-m-36954c.html> [Accessed 18 June 2020].
10. Nelson Labs. 2020. Medical Face Masks Flammability | Nelson Labs. [online] Available at: <https://www.nelsonlabs.com/testing/flammability-test/> [Accessed 18 June 2020].