Why and when to replace your respirator particulate filter

3M’s Mark Reggers answers some commonly asked questions.

What guidance is available in selecting the correct respirator and filters?

There are two Australian Standards that pertain to respiratory protection. AS/NZS1715 is for the user and is called “Selection, use & maintenance of respiratory protective devices”.

The second, AS/NZS1716 provides the information required to assess and test the performance requirements the different types of respiratory protection products must meet.

What types of filters are there?

There are three types of filters:

  • Particulate filters: Protect only against particles i.e. dust, mists and fumes, aege of the respiratory hazards in the workplace.rosols, smoke, mould, bacteria and so on.
  • Gas and vapour cartridge filters: Protect only against gases and vapours. There are different kinds of gas and vapour cartridge filters for different kinds of gases.
  • Combination filters: Protect against both particles and gases. Different combination particulate/cartridge filters are used depending on the gas or vapour present in the air.

Why do I need to replace my filters regularly?

Particulate filters get clogged up and become harder to breathe through placing an increased physiological burden on the wearer.

Gas and vapour cartridge filters start to let contaminant through once their sorbents become saturated. This is known as ‘breakthrough’. It’s important to note that the selection of filters must be carried out by a competent person with a full knowledge.

What’s a P1? P2? P3?

AS/NZS1716 uses a classification system to identify the different types of particulate filters which are P1, P2 and P3.

P1 is an AS/NZS1716 rated particle filter for use with mechanically generated particles. For example; particles formed by crushing, grinding, drilling, sanding, cutting etc including wood dust and silica.

P2 is an AS/NZS1716 rated particle filter for use with mechanically and thermally generated particles, for example; those from welding fume. These are also the recommended type for use with certain biological particles in certain applications such as TB or SARS.

A P3 filter is the highest efficiency particle filter class and is used for particulates that are of high toxicity or at high concentrations. The benefit of this high efficiency filter can only be achieved on a full facemask or head covering respirator system.

How long do particulate filters last?

As particle filters load up with the contaminant, they become more restrictive to the passage of particles and can be a better filter. However, they also become harder to breathe through.

The wearer will notice this increased load and at some point decide the restriction is too high and will then need to change the filter. How soon this occurs will also be dependent on the amount of particles in the breathing air.

A very dusty job will clog the filter up more quickly than a relatively clean job. The change decision point will vary from individual to individual as some people are more sensitive to the increase in breathing load than others.

When do I replace my particulate filters?

Replace particulate filters or disposable respirators when:

  • The breathing resistance becomes excessive to the wearer (this will vary from individual to individual).
  • The filter has any physical damage e.g. welding sparks

Are there situations where particulate filters must not be used?

There are several applications where particle filters should not be used. These include:

  • When the ambient oxygen level is not guaranteed to be more than 19.5 per cent. Filters do not create oxygen.
  • For the capture of gases or vapours. These need a specifically rated gas/vapour filter.
  • When the airborne particulate contaminant concentrations are high (ie greater than the standard allows for that respirator type).
  • When government regulations require use of airline or other specific type of respirator for specific applications.

Remember, selecting the correct filter or cartridge is one part of the equation in achieving respiratory protection. A respirator must be worn 100 per cent of the time to achieve any level of protection.

The mask in question must also be fitted and worn correctly each and every time it is worn. We all have a different face shape and size, so fit testing is required to verify that an adequate seal can be achieved for the brand/style of mask and the worker.

It doesn’t matter how good a filter is, if the contaminant can still enter the mask because of a poor or non-existent seal.

For further information on when and why to change gas and vapour filters, respirator selection, respirator fit testing please refer to AS/NZS 1715 “Selection, use & maintenance of respiratory protective devices”.

Mark Reggers is an occupational hygienist for 3M Personal Safety Division, and the host of 3M’s Science of Safety podcast 

This first appeared in the May/June issue of INCLEAN magazine. 

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