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Quick Guide: Respirator Filters and Cartridges

Credit: Canva Premium

Important note before you start reading: The information provided in this article is not intended as specific advice or guidance for your workplace, as every situation is unique. It is essential to consult with a certified occupational hygienist or a qualified health and safety professional for the appropriate selection and use of respiratory protective equipment (RPE), especially in environments with complex and various airborne contaminants.

Respirator filters are critical components that determine the protective capabilities of respiratory equipment.

Particulate filters trap solid and liquid particles suspended in the air, such as dust, mists, and aerosols. They come in various efficiency levels, classified by their ability to filter out particles of different sizes.

Gas/vapour cartridges are designed to protect from harmful chemicals, gases and vapours in the air. These cartridges contain specialized materials - such as activated carbon - that chemically react with or absorb specific airborne chemicals, neutralizing their effects and ensuring the wearer breathes in cleaner air.

It's crucial to select the appropriate filter type based on the potential hazards present in your work environment.

You should also ensure that any filters you choose are certified via the AS/NZS 1716:2012. This Standard specifies the requirements, performance and testing criteria for the manufacture of respiratory protective equipment and filters.

In this post, we'll cover some of the most common questions we get asked about filters.

What are the various types of particulate filters?

In Australia, respirator particulate filters are classified based on their efficiency in filtering out airborne particles such as dust (e.g. silica dust) and bioaerosols (e.g. viruses).

Classification of Filters

  • P1 Filters: Filter ~80% of mechanically generated particles

  • P2 Filters: Filter ~ 94% of mechanically and thermally generated particles

  • P3 Filters: Filter ~ 99.95% of mechanically and thermally generated particles.

Which class of filter you need will depend on the hazard you're exposed to and to what extent.

P1 and P2 filters can come in disposable respirators (aka filtering facepiece respirators such as N95s and P2s) or be attached to reusable respirators. See pic below.

In Australia, there are no disposable P3 respirators. Per an AS/NZS 1715 ruling, all respirators that cover just the nose and mouth (disposables and reusable half-face respirators) can achieve only a P1 or P2 classification. A P3 classification can only be achieved when worn with a full-face respirator. When a P3 filter is on a half-face reusable respirator, the protection class is equivalent to a P2.

A side note: N95 vs P2

When it comes to disposable filtering facepiece respirators, there's some confusion about N95 vs P2.

The N95 filter is the rating used in the United States (certified through NIOSH), while the P2 filter is its equivalent in Australia and New Zealand (certified under the AS/NZS 1716). Both filters are tested and certified to filter out at least 95% and 94% of airborne particles respectively.

What are gas and vapour cartridges?

Gas and vapour cartridge categories are distinguished by their filter type and class. The cartridges are labelled with letters and colours that indicate the type of chemical they provide protection against.

For example, a respirator cartridge intended to protect against sulfur dioxide would be denoted with an 'E' and be coded with the colour yellow.

It's important to note that gas and vapour filters alone are not effective in safeguarding against particles.

Common Types:

Credit: 3M

The filter's absorption capacity is denoted by its Class. The absorption capacity is represented by the following classes (from lowest to highest absorption capacity): Class AUS, Class 1, Class 2, and Class 3.

Gas/vapour cartridges come in various combinations. For example, you may see an A filter alone (protects only against organic gases/vapours) or an ABEK (protects against organics, acid gases, inorganics and ammonia). The absorption capacity Class will also be noted on the cartridge.

Some gas/vapour cartridges also have particulate filters to protect against airborne particles. These are called combination filters.

You need to know what hazard you're trying to protect yourself or your employees from to make sure you choose the right filters.

How often do I change my filters?

Regular replacement of filters is essential to maintain the respirator's efficiency and protect you from harmful airborne contaminants.

The service life of any filter depends on several factors including the airborne concentration of contaminants, exposure times, user breathing rates, humidity levels, and temperature.

Here are the general rules of thumb for changing particulate and gas/vapour filters.

Particulate Filters

  • According to the expiry date stamped on the sealed packet

  • Breathing becomes more difficult

  • The filters are damaged or visibly dirty

  • According to a filter change schedule for your workplace

Interestingly, as particulate filters load up with contaminants, such as dust, they filter more efficiently. However, they also become harder to breathe through.

How often filters need to be changed will vary from person to person and is dependent upon many factors including airborne contaminant levels, work time, and breathing rate.

Gas/Vapour Cartridges

  • According to a workplace change schedule - this is the best method.

  • According to the expiry date stamped on the sealed packet.

  • Once opened, the maximum use time is 6 months. Write the date on the cartridge .when you open it.

  • When contaminant can be detected by smell or taste (keep in mind that not all gases/vapours have a taste or odour). This is called breakthrough. Never rely solely on breakthrough as a change indicator.

  • The cartridges are damaged.

If you know your air concentration levels of particular gases and vapours, you can use the 3M Select and Service Life software to estimate when gas/vapour cartridges must be changed.

Always refer to manufacturers' instructions for your particular filters or cartridges.


We hear this ALL the time. Folks attempt to clean their filters using compressed air or "giving them a good shake."


Attempting to clean respirator particulate filters by using compressed air or vigorously shaking them out is just not right.

These filters are designed with intricate layers and fibres that are precisely engineered to trap and capture harmful particles, such as dust, pollutants, and microorganisms. Introducing compressed air or aggressive shaking can disrupt this delicate structure, potentially causing irreversible damage to the filter's efficiency and effectiveness.

Moreover, the force applied might dislodge trapped particles, releasing them into the air and increasing the risk of inhalation. Instead, change filters according to the advice in this article and always follow manufacturer guidelines for filter replacement.

To Wrap it All Up

There are lots of factors that go into choosing the right filters or filter combinations for your workplace.

Just remember:

  • Particulate filters are used for protection against liquid/solid particles such as dust and viruses.

  • Gas/vapour filters (cartridges) protect against chemicals, gases and vapours.

  • To choose the right filters, a risk assessment is required to identify your airborne hazards.

  • If you need protection against both particles and gas/vapours, choose combination cartridges.

  • Be sure your filters are AS/NZS 1716 certified.

  • As a general rule of thumb - particulate filters should be changed when breathing resistance increases.

  • Gas/vapour filters should be changed according to a schedule. Change immediately if you can smell/taste anything but never rely solely on this method as a change indicator.

  • How often you need to change filters depends on many factors including airborne concentration levels, breathing rates, temperature, humidity, etc.

  • NEVER, EVER shake out filters or use compressed air to try to clean them. They are disposable and must be changed when full.

If you have questions, feel free to call us at 0428 630 109 or email

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All rights reserved. No part of this blog post may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the copyright owner.


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