Testing respiratory devices to the EN 136 standard

Investigating the assessment of full-face masks in line with this key legislation.

Respiratory protective devices are intended to protect against hazardous substances in the air – such as particles, vapours and gases – by means of a filtering mechanism. These devices are made of a reusable structure fitted with replaceable filters.

Full-face masks are designed to cover the entire face, including the eyes, nose, mouth, and chin, and provide a seal against specific atmospheric conditions and airborne hazards. They are categorised into three classes: Class 1 (used for light duty), Class 2 – for general use, and Class 3 (‘special use’). In this article, we will delve into the intricacies of testing face masks to the EN 136 standard.

A look at the standard

The EN 136:1998 standard specifies the performance requirements, test methods and marking requirements for full-face masks that incorporate filters and which are used as respiratory protective devices.

Compliance with this standard signifies that a face mask meets stringent criteria regarding filtration efficiency, breathing resistance, ergonomic design and compatibility with various facial shapes and sizes. Manufacturers aiming to achieve compliance to EN 136 must adhere to meticulous guidelines throughout the production process to ensure their masks’ efficacy and safety.

The standard defines performance requirements for different types of masks. A mask conforming to the standard must have its class written on it, along with the name of the standard and its year of publication, as well as applicable codes to denote any limitations of use.

Within EN 136:1998, full-face masks are classified in one of the three classes, according to their breathing resistance, flammability and mechanical properties (such as having head straps).

Testing

EN 136:1998 is the current harmonised European standard for full-face masks used as respiratory protective devices. For this type of mask, filters are tested separately to the mask to ensure compliance with specific standard requirements.

The table below shows a summary of the key testing and performance requirements.

Key testing and performance requirements
Test	Brief description	Requirement
Breathing resistance	The breathing resistance test apparatus measures the drop in pressure across the mask during inhalation and exhalation. Depending on the class of the mask, the pass/fail criteria will change. The higher class of mask will have stricter requirements. This test ensures that the mask functions correctly.	The mask shall provide adequate inhalation and exhalation resistance so that the user can safely breathe.
CO2 content of inhalation air	This test involves the mask in a simulated wear position with CO2 incorporated. A measurement is taken as the mask replicates an inhalation to assess how much CO2 is retained in the mask and inhaled, compared to how much is leaving the mask through the exhalation valves.	The CO2 content of the inhalation air shall not exceed 1 per cent by volume.
Flammability	Samples are fitted onto a metallic head form. The head form wearing the mask is then passed through a small flame (for class 1 masks) in the position as it is worn. For class 2 and 3 masks, there are six separate burner flames lit at the same time at a much higher temperature. The mask must withstand this heat after being exposed to it for five seconds. Testing is repeated to ensure all materials of the mask are tested.	The mask must not continue to burn for longer than five seconds after removal from the flame.
Inward leakage	The Inward leakage test involves the use of subjects and apparatus to measure the masks’ ability to provide a proper seal against the face. This is judged by the participant correctly wearing the face mask and performing walking tasks. Continuous readings from within the mask are taken to check how much of the solution is detected.	The inward leakage of the test agent must not exceed an average of 0.05 per cent of the inhaled air for any of the ten test participants.
Materials	The suitability of materials used is checked by conducting various tests. These tests range from high and low temperatures, resistance to cleaning chemicals and participant comments.	Based on the results of: temperature conditioning cleaning and disinfecting cycle innocuousness practical performance.
	‘Temperature conditioning’ is to test if the product can withstand different temperatures and humidities without deformation. The conditioning cycle is: 24 h in a dry atmosphere at 70°C 24 h at -30°C.	No deformation of the sample after the conditioning periods.
	On reusable masks, a cleaning and disinfecting cycle is used to see if this process changes the product materials in any way. This will be assessed during the inward leakage test and penetration testing, as well as a visual check.	No deformation or damage to the sample after the cleaning and disinfecting process. The inward leakage and penetration tests shall still meet the relevant requirements as per the mask rating.
	Innocuousness testing is also conducted to ensure that the materials used are safe, without adverse effects to health.	The mask shall not contain chemicals that may harm or irritate the wearer.
Practical performance	This test is used to check the product for possible issues that would not be found during other testing. This can include mask comfort, fitting of the headband and field of vision. The test consists of two exercises: Walking test – This consists of walking on a level surface for ten minutes at a rate of 6 km/h with the mask donned correctly. Work simulation test – This consists of three exercises to simulate the mask being used for a full work session. walking on a level with headroom of 1.3 m crawling on a level with headroom of 0.70 m filling a small basket with chippings and emptying them into a hopper for ten minutes.	This test is subjective and pass/fail is based on the comments of the individual. Each part is assessed on its own, so only one part could fail or all parts. Mask comfort: assessment based on how comfortable the mask is to wear during use. Headbands: assessment based on whether the headbands hold the mask in position for the duration of the exercises, as well as if the headbands are easy to use and comfortable.
Leak tightness	The full-face mask shall not show a change of pressure of 1 mbar a minute when being subjected to a pressure of -10 mbar.	The mask shall continue to be leak tight after each test has been conducted on it.
Eyepiece	A 43.8 g steel ball is dropped down a tube of 1.3 m onto the eyepieces of the mask.	Eyepieces shall be leak tight. Eyepieces shall not distort vision. Anti-misting agents shall be applied to the visor to reduce the effects of fogging. After the drop test, the eyepieces shall not be damaged in any way that could cause injury to the wearer.

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