Filter Guide
*Chart copyright of HSE

Choosing the correct filter can seem quite complex with the range of colour coding and wide range of choices available, but here are a few simple rules to follow:

For protection against particles a particle filter needs to be selected – Particles consist of dust, mist, sprays, aerosols, fumes (P3 only) etc. The smaller the particle the higher the efficiency needed to protect you. These are colour coded white and abbreviated to a ‘P’ for particle filter. Three grades of particle filters are available according to their efficiency:

P1 = Low Efficiency 80% - APF 4
P2 = Medium Efficiency 94% - APF 10
P3 = High Efficiency 99% - APF 20

In most instances the HSE are now recommending P3 filters for most environments where a particle filter is recommended. If in doubt, please call our team of RPE experts who can give advice on your particular requirements.

For protection against gases or vapours a number of filter options are available in different grades to show how much of contaminants that they can hold and are suited to different environments:

Class 1 – Low Capacity
Class 2 – Medium Capacity
Class 3 – High Capacity

A = Organic Gases (Brown)
B = Inorganic Gases (Grey)
E = SO² and other Acid Gases (Yellow)
K = Ammonia (Green)



These filters also have single or multi-gas options available.


Combined filters are available for environments where both particles and gases are present. These filters have a ‘P’ in their code and one or all of the gas filters ‘A’, ‘B’, ‘E’ and or ‘K’.

If you are unsure of the filter you require please contact us or call our team of RPE experts for advice on 01933 672 180. For Respiratory advice please download our questionaire and send it back to info@rpeexperts.co.uk.