top of page


Updated: Feb 17


There are different types of Respirators (Disposables, Half Face mask, Full Face mask, Hood, Helmet, PAPR etc.) and different types of filters (gas & vapor filters, particle filters, combined filters).

With so many types of filters on the market, you can quickly feel overwhelmed by the wide range of references and brands. Choosing the correct filters for your workplace is just as important as selecting the right type of Respiratory Protective Equipment (RPE) for the task at hand. Please read on for an overview of all types of filters available, their colour code, efficiency class, and other relevant aspects.


Did you know?

An aerosol is a mixture of tiny solid particles or liquid droplets suspended in air or another gas, these particles exhibit a descending speed of less than 0.25 m/s, which, under regular atmospheric conditions, means they have dimensions smaller than 100 µm.

Gas Filters

Gas filters provide protection against vapors, chemical substances and toxic gases. They usually consist of a bed of activated carbon. They are described according to 2 criteria: filter type and class.

The various types of gas filters and how they are defined

The specific filters for the different types of gas or family of gases or vapors is indicated through marking consisting of a letter and a strip of a certain colour.

Different types of gas filters are defined by a marking comprising a letter and a strip of specific colour. In cases where a filter is designed to safeguard against multiple families of gases, we call this a combined filter and is identified by the juxtaposition of a letter and the corresponding colour stripes.

Moldex Filters

For example:

AB = Filters organic gases/vapors and inorganic gases/vapors BK = Filters inorganic vapors, ammonia and ammonia derivatives

Selecting the right class of efficiency for your gas filter

As for aerosol filters, there are three classes of protective filters based on their capacity (in other words, the best balance between volume and effectiveness of the absorbent material):

  • Class 1: For gas concentrations of less than 0.1% by volume, the lowest capacity (filters for half masks) – e.g.: A1

  • Class 2: For gas concentrations of between 0.1% and 0.5% by volume, medium capacity (cartridge) – e.g., ABEK2

  • Class 3: For gas concentrations of between 0.5% and 1% by volume, the largest capacity (large-capacity canister worn at waist-level)

At an equivalent ambient concentration level, a class 3 filter will operate for longer than either a class 2 or a class 1 filter.


Some examples of gases:

A: xylene, styrene, phenol, white spirit, etc. B: SO₂, H₂S, Cl₂, etc. E: nitric acid, etc. K: ammonia derivatives AX: acetone, butane, methanol, etc.

Note: There are some manufacturers that offer specific filters exclusively for carbon monoxide (CO) protection, to be used with life-saving and evacuation devices or deemed for escape use only.

What is the expected life of my gas filter?

A gas filter ceases to function properly when the carbon granules become saturated. It starts allowing pollutants in with which it is in contact. For this reason, gas filters need to be replaced on a regular basis, this is essential prior to the filters becoming totally saturated.



Aerosol and Particle Filters

Particle filters provide protection against asbestos, dust, mists, liquids and some fumes, micro-organisms, viruses and bacteria but not gases or vapors

How to identify a particle filter

Particle filters are identified by their characteristics, which are printed directly on the mask. FF stands for Filtering Facepiece, while P1, P2 and P3 refer to the class of filter efficiency. There is no difference between FFP2 and P2. FFP2 stands for “Filtering Facepiece P2”. You will notice it is most commonly abbreviated to just “P1 or P2”.

On filtering cartridges, this information is shown on a white strip marked either P1, P2 or P3. Filtering facepieces (disposable respirators), also referred to as dust masks, are particulate filters, they are usually FFP1 or FFP2. Disposable masks only cover the wearers mouth and nose. It is important to note appropriate use of your P1 or P2 and what contaminations they should be used for.

How to select the right class of efficiency for your particle filter

The different particle filter classes:

  • Class 1 (P1) Least filtering Filters at least 80% of airborne particles (means that fewer than 20% of particles pass through the filter) Offers protection against solid particles that are not specifically toxic (calcium carbonate, etc.)

  • Class 2 (P2) Intermediate efficiency Filters at least 94% of airborne particles (means that fewer than 6% of particles pass through the filter) Offers protection against hazardous and irritant airborne particles in solid and/or liquid form (silica, sodium carbonate, grinding, cutting, sanding, drilling, sawing etc. Viruses and bacteria)

  • Class 3 (P3) High level of efficiency Filters at least 99.95% of airborne particles (means that fewer than 0.05% of particles pass through the filter) Offers protection against toxic airborne particles in solid and/or liquid form (beryllium, nickel, uranium, welding fumes, fertilizer and bushfire smoke etc. Viruses and bacteria)

P3 Rating can only be achieved when used with a Full-Face Respirator or Powered Air-Purifying Respirator (PAPR). If used with any other respirator, it will only provide filtration protection up to a P2 rating.

The service life of particle filters depends on the environment. The filters will start to become clogged over time and restrict the amount of air coming through to the breathing zone. When it becomes difficult to breathe, it is a key indicator the filter is getting to the end of its service life and needs to be replaced.

Note: Fit Test Australia suggests writing the date on your filters once opened and attached to your respirator as a reference point.

Distinguishing between a P2 vs N95


What sets them apart?

In the world of disposable filtering facepiece respirators, a degree of ambiguity arises surrounding N95 vs. P2 filters. The N95 rating pertains to the United States (certified by NIOSH), while the P2 rating serves as its Australian and New Zealand equivalent (endorsed under AS/NZS 1716:2012). Both filters are meticulously evaluated and certified to filter out at least 95% and 94% of airborne particles, respectively. Typically, N95 masks tend to have a Level 3 rating deeming them suitable for the HealthCare Sector making them a medical grade as they require masks to have a higher level of fluid protection for aerosol generating procedures (AGPs), sprays and/or fluids. You will see P2 masks with a Level 3 rating deeming them suitable for the HealthCare Sector also.

Combined filters

Combination filters used for protecting yourself against airborne particulate, gases and vapors

Combination filters are designed to offer the wearer protection against airborne particulate, gases and vapors simultaneously. They are made up of both a particle filter combined with a gas filter. These can be distinguished by dual marking: the coloured strip for gas filters plus the white strip for particle filters.

Example: A2B2P3 filter

A filter with the colour code shown opposite is suitable for the following contaminants:

A: Gas and vapors of organic compounds with a boiling point ≥ 65°C, up to the concentrations covered by a class 2 filter (5,000ppm) B: Inorganic gases and vapors up to the concentrations covered by a class 2 filter (5,000ppm) P: Particles up to the concentrations covered by a class 3 filter

Fit Test Australia advises against using any respirators that has no certification or standards marks on the device or packaging.

Key Takeaways


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

  • Gas/vapor filters (cartridges) protect against chemicals, gases, and vapors.

  • To choose the right filters, a risk assessment is required to identify your airborne hazards and concentration levels, read more at Safe Work Australia & WES.

  • Should you need protection against both particles and gas and/or vapors, choose combination cartridges.

  • Be sure your filters are AS/NZS 1716:2012 certified, this is a must.

  • Best guidance - particulate filters must be changed when breathing resistance increases and gas/vapor filters changed if you can smell/taste chemicals.

  • How often you need to change filters depends on many factors including airborne concentration levels, breathing rates, temperature, humidity, time spent in the contaminated/hazardous area and/or if persons in the area experience nose and/or throat irritation etc.

  • Schedule for filters to be changed on a regular basis.

  • Fit test your respirator to ensure you are wearing the correct size, make and/or model as all our faces are unique. Book your fit test here.

Your health and safety is our priority

Call: 0403 064 064

FTA fit test Melbourne Victoria and Sydney NSW 

Fit Test Australia | Correct Filter Protection

168 views0 comments

Recent Posts

See All


bottom of page