Gas mask filters

The efficiency of a powered air purifying respirator primarily depends of the gas mask filter selected to protect against present gas, vapor or particles. The most difficult is to select the proper respirator cartridge according to the potential hazards. Moreover, any air purifying respirator is efficient only if the oxygen rate in ambient air exceeds 19.5% of the volume.

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Particulates respirator cartridge (example: P3 filter)

Particle filters – also known as aerosol gas mask filters – are mainly used to protect users against dusts, particles, liquid and solid aerosols according to the EN143 standard. They are gathered into 3 efficiency classes (P1, P2 or P3) that ensure a purifying level from 80% to 99.97%.

EN143 particulates filter’s capacity

ClassDescriptionEfficiencyUsage limits
P1Low efficiency (against coarse solid particles and slightly harmful)Stop at least 80% of this aerosol (penetration below 20%)4 x TWA value
P2Intermediate efficiency (against harmful solid and liquid particles)Stop at least 94% of this aerosol (penetration below 6%)12 x TWA value
P3High efficiency (against toxic solid and liquid particles, radioactive particles and micro-organisms)Stop at least 99,95% of this aerosol (penetration below 0,05%)With half mask: 30 x TWA value With full face mask: 400 x TWA value

Particle filters for air purifying respirators feature a large parallel pleated purifying surface which avoid clogging risks in very dusty environments. Because of their hydrophobic characteristic they are water resistant and stop the thinnest particles.

In a dusty environment, particulates filter will progressively clog and offer a higher and higher breathing resistance – without affecting the purifying power. This breathing disturbance will determine the filter replacement.

Gas filter (example: ABEK filter)

Gas filters for APR respirators are especially designed to get protected against toxic substances. These gas mask filters feature a microporous structure made of active carbon with tiny capillaries for an enhanced purifying efficiency while reducing the breathing effort. As for particle filters, they are gathered into 3 efficiency classes, ensuring a purifying level (3 being the maximum protection level). In addition to the three efficiency levels, there is a specific codification composed by letters and colors for different types of toxic gas and substances.

Gas classColor codeApplication
A
Organic gas and vapor (solvents) with boiling point above 65°C
AX
Organic gas and vapor with boiling point above 65°C
B
Inorganic gas and vapor (chlorine, hydrogen sulfide, hydrocyanic acid)
CO
Carbon monoxide
E
Acid gas and vapor like sulfur dioxide
Hg
Mercury vapors
I
Iodine
K
Ammonia and organic derivatives
NOx
Nitric oxide, nitrogen oxide, nitrous vapor

Some respirator cartridges can combine simultaneously several gases. This way, a gas mask filter cartridge against organic and inorganic gas and vapor, acids and ammonia – and its derivatives – will be labeled ABEK with a color code brown, grey, yellow, green.

Gas and particle combined filter (example: ABEK2-P3 filter)

As their name implies, combined filters are efficient both against dusts and toxic substances. Because of this virtually unbeatable protection level in the field of air purifying respirator cartridges they are slightly larger than standard gas mask filters. Their operating principle is very easy to understand: inspired air goes first through the aerosol particle filter (like oil or paint droplet e. g.) before going through the gas filter.

ClassApplication
A2-P3Organic gas and vapor (solvent) with a boiling point above 65°C, solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
B2-P3Inorganic gas and vapor (chlorine, hydrogen sulfide, hydrogen cyanide), solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
E2-P3Acid gas and vapor like sulfur dioxide, solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
K2-P3Ammonia and organic derivatives of ammonia, solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
A2B2-P3Organic and inorganic gas and vapor, solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
A2B2E2K2-P3Organic and inorganic gas and vapor, acid gas and vapor, ammonia, solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
AX-P3Organic compound gas and vapor with a boiling point at or below 65°C, solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
Reactor-Hg-P3Mercury and compounds, radioactive iodine and organic compound (methyl iodine), solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
A1E1Hg-P3Acid, organic and inorganic gas and vapor, ammonia and organic derivatives, mercury vapor and compounds, solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses
A2B2E2K2-Hg-P3Acid, organic and inorganic gas and vapor, ammonia and organic derivatives, mercury vapor and compounds, solid and liquid particles, highly toxic and radioactive particles, bacteria and viruses

Given that these gas mask filters are airtight to aerosol particles, they are often chosen for liquid spraying works such as painting.