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How Often Should I Change My Filters?

Updated: Jan 9

Great question! And one we, at Fit Test Victoria, get asked a lot!

This article discusses how often you should change particulate filters and gas/vapour cartridges for non-powered, reusable half-face and full-face respirators.

Particulate filters protect against particles such as dust, mists, fumes, smoke, mould, bacteria and viruses.

Gas and vapour cartridge filters protect against, you guessed it, gases and vapours.

Filters that attach to reusable respirators can be particulate only, gas/vapour only or a combination of the two.

Let's jump right in.

How Often Should I Change Particulate Filters?

First, let's do a quick overview of the various types of particulate filters.

The AS/NZS 1716 standard specifies requirements, performance and testing criteria for respiratory protective equipment in Australia. Their classification system for particulate filters are:

  • P1 - Filters out ~80% of mechanically generated particles

  • P2 - Filters out ~94% of mechanically and thermally generated particles

  • P3 - Filters out ~99% of mechanically and thermally generated particles. P3 filters only achieve P3 level of protection when used with full face respirators. P3's can be used on half face respirators, but the protection level drops down to P2.

Now, back to the question. How often should particulate filters be changed?

Particulate filters are composed of electrostatically charged fibres that trap fine particles such as dust, smoke, fumes, mists, bacteria and viruses, As these filters load up with particles, they become more efficient. But they also become harder to breathe through.

The general rule of thumb is that particulate filters should be changed when the wearer notices that breathing has become more difficult. This means the filter is "loaded" and needs to be replaced.

Filters should also be changed if they are visibly damaged or dirty.

The big problem with this thumb rule is that some people don't notice increased breathing resistance, even if their filters are full.

And it can be tricky to tell if a filter is dirty, especially filters encased in a hard shell. Or where the contaminant isn't noticeably grimy. For example, white-coloured dust or debris doesn't necessarily appear "dirty."

How often filters will need to be changed varies considerably depending on the amount of airborne contaminant, exposure times and personal perceptions of increased breathing resistance.

Always refer to manufacturers' instructions for brand-specific advice on filter changes.

How Often Should I Change Gas/Vapour Filters?

Gas and vapour filters typically use carbon grain to absorb gas and vapour molecules. The carbon grain can be chemically treated to soak up different types of gases and vapours.

The AS/NZS1716 uses a colour-coded classification system to identify the different types of contaminants that can be captured. See the chart below.

Credit: 3M

The service life of gas and vapour filters is dependent upon many variables including:

  • Concentration of airborne contaminants

  • Exposure times

  • Work of breathing / breathing rate

  • Temperature and humidity

The general rule of thumb that indicates a gas/vapour cartridge needs to be replaced is when a contaminant can be smelled or tasted. This is called breakthrough. Keep in mind that not all contaminants have an odour or a taste.

Other times to change your gas/vapour filters:

  • According to the expiry date on the packet

  • Once opened, the use time is no more than 6 months as the carbon will continue to absorb contaminants from the environment (even when not in use by the wearer). Write the open date on the cartridge.

  • Following a filter change schedule

3M has a service life software that can help you determine the service life of gas/vapour filters. To use this tool, you'll need to know the airborne contaminant levels determined via air monitoring.

How Often Should I Change Combination Filters?

If the filter on your respirator is a combination filter that has both particulate and gas/vapour components, here's what you do.

If the gas/vapour cartridge has a particulate pre-filter that can be removed and changed - like the photo below - you follow the same rules for changing any particulate filter - when breathing resistance becomes unacceptable. And you'd change the gas/vapour component when breakthrough occurs, according to your workplace's change schedule, or if it has been 6 months since the cartridge was opened.

Credit: Maxisafe. You can remove the particulate pre-filter that is attached to the gas/vapour cartridge.

If the gas/vapour cartridge has the particulate filter built in, you can't change the individual parts. The photo below is an example of an all-in-one combo filter (ABEKP3). In this case, you'd have to change the filter if breathing resistance increases or when there's breakthrough, whichever happens first. Additionally, if 6 months have gone by since the filter was opened, it will need to be changed.

Credit: JSP This is a combine gas/vapour/particulate filter. Individual components can't be changed


Wrapping Up

We hope this helps you gain a better understanding of when to change the filters on your reusable respirators.

To recap:

  • Particulate filters should be changed when the wearer notices increased breathing resistance.

  • Gas and vapour filters should be changed when the wearer can start to taste or smell the contaminants, after 6 months of being removed from the package or according to a change schedule.

  • Keep in mind that not all gases and vapours have an odour or taste.

  • 3M has a free service life software that can be used to gauge when gas/vapour filters should be changed. You have to know the air concentration levels of the contaminants to use this tool.

Interested in expanding your knowledge about respiratory protective equipment? Call us at 0488 688 454 to learn more about our RPE Courses.

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