Respiratory protective filters: color code, class, ...

Why is a filter an important part of respiratory protection ?

Four European standards have been introduced, defining the respiratory protection filters to be used in each case: (see standards & regulations for respiratory protection)

• NF EN 14387 : Gas filters and combination filters
• NF EN 143 : Particle filters (new legislation P1 2 3 anti-dust R reusable, Non Reusable 2009)
• NF EN 372 : SX gas filters and combination filters against specific combinations designated 14387
• EN 149 : Disposable masks

There are 3 types of filters (gas filters, aerosol filters and combined filters), providing protection against two types of toxic contaminants :

• Aerosols : dust, particles, fibres, fumes, micro-organisms such as viruses and bacteria
• Gaseous substances : gas and vapours

Gas filters

Gas filters protect against toxic vapors, chemicals and gases. They are generally made of activated carbon. They are designated according to 2 criteria: filter type and class.

> How to define gas filter types ?

A filter specific to a gas or family of gases or vapors is designated by a marking consisting of a letter accompanied by a specific color band. If the filter is designed to protect against several families of gases at the same time, it is referred to as a mixed filter: it is designated by a juxtaposition of letter markings and the corresponding color bands (page 108 of the catalog).

For example:

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

> How to choose a gas filter efficiency class ?

As in the case of aerosol filters, there are three classes of protective filters, depending on their trapping capacity (i.e. a compromise between the volume and efficiency of the adsorbent material) :

• Class 1: For a gas content of less than 0.1% by volume, i.e. the lowest capacity (wafers) - Ex: A1
• Class 2 : For a gas content of between 0.1% and 0.5% by volume, i.e. the average capacity (cartridge) - ex ABEK2
• Class 3 : For gas contents of between 0.5% and 1% by volume, i.e. the largest capacity (large-capacity belt-worn cans).

At the same ambient concentration, the autonomy of a class 3 filter will be longer than that of a class 2 filter and consequently a class 1 filter.

> A few examples :

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

Note: Some manufacturers offer specific filters that provide protection against carbon monoxide (CO). These are reserved for evacuation or survival devices.

> How long is a gas filter effective for ?

When saturated, a gas filter becomes inoperative. It then lets through all the pollutants to which it is subjected. A gas filter must therefore be replaced periodically before it becomes completely saturated.

It is important to know the minimum breakdown time required by standard NF EN 14387 +A1 :

Aerosol or particulate filters

Particle filters provide protection against dust, fumes, micro-organisms and viruses.

> How to recognize particulate filters ?

Particle filters can be identified by the characteristics printed directly on the mask. FF stands for Faciale Filtrante and P1, P2 or P3 for the filtration class. On filter cartridges, this is indicated by a white band with P1, P2 or P3 on it.

> How to choose the particulate filter efficiency class ?

The different particle filter classes:

• Class 1 (P1) Low efficiency :
  Stops at least 80% of this aerosol (i.e. less than 20% penetration)
  To protect against solid particles of no specific toxicity (calcium carbonate...)
   
• Class 2 (P2) Medium effectiveness :
  Stops at least 94% of this aerosol (i.e. less than 6% penetration)
  To protect against dangerous or irritating aerosols, solid and/or liquid (Silica, sodium carbonate...)
   
• Class 3 (P3) High Efficacy :
  Stops at least 99.95% of this aerosol (i.e. penetration less than 0.05%)
  For protection against toxic solid and/or liquid aerosols (beryllium, nickel, uranium, etc.)

> How long is a particulate filter effective ?

The life of particulate filters depends on the environment. Filters will gradually become clogged, and offer increasing resistance to the passage of air. Respiratory discomfort will determine the length of use and frequency of replacement.

Combination filters

> How to protect yourself against airborne particulate, gases and vapours, all at the same time

Combination filters are designed to protect against aerosols, gases and vapors. They consist of a particulate filter and a gas filter superimposed on each other. They can be recognized by their double marking: the colored stripe for gas filters and the white stripe for particulates.

Example: A2B2P3 filter

A color-coded filter is suitable for the following contaminants :

• A: Gases and vapors of organic compounds with boiling point ≥ 65°C up to concentrations covered by a class 2 filter (5000 ppm)
• B: Inorganic gases and vapors up to concentrations covered by a class 2 filter (5000 ppm)
• P: Particles up to concentrations covered by a class 3 filter