Gas masks and filters

Masks

A mask is only as good as its seal and the filter on it. Seal is the share of your breath that comes through the filter instead of leaking in round the edge, and breathing effort and sprint cost are what wearing it takes out of you.

Mask	Filter it takes	Covers the eyes	Seal	Breathing effort	Extra sprint stamina	Lens fogging	Your voice	Put on	Take off	Change filter
Military Gas Mask	40 mm screw-on canister	Yes	99.9%	x1.12	0.55 /s	x0.35	Clearer (voice emitter)	7 s	2 s	7 s
Full-Face Respirator	40 mm screw-on canister	Yes	99.5%	x1.1	0.5 /s	x0.6	Muffled	6 s	2 s	7 s
Half-Face Respirator	Twin bayonet cartridges	No	98.5%	x1.05	0.35 /s	x0	Muffled	3.5 s	1.5 s	9 s
Surplus Gas Mask	40 mm screw-on canister	Yes	93%	x1.35	1 /s	x1.4	Muffled	8 s	2 s	8 s
Improvised Gas Mask	40 mm screw-on canister	Yes	82%	x1.4	1.1 /s	x1.6	Muffled	9 s	2.5 s	8 s

A mask in poor condition seals worse: below 60% condition the seal falls away, down to 85% of itself at 0%. Below 35% the lens is cracked, which leaks more and lets 35% of an irritant reach your eyes.

A mask with no filter on it protects your eyes but not your lungs, and a mask pulled down to your neck protects nothing.

You hold your breath while you change a filter, which drains 7 stamina a second. If you run out, you breathe whatever is around you for the rest of the change.

You cannot eat, drink, smoke or take pills with a mask sealed on your face.

Filters

A filter stops particles (smoke, dust, spores, tear gas), gases, or both, and it only fits masks with the same fitting. The figures are for a fresh filter.

Filter	Fitting	Particles stopped	Gas stopped	Weight	Breathing effort when spent	Gas breaks through in the last
Multi-Gas Cartridges (Pair)	Twin bayonet cartridges	99.97%	99%	0.28 kg	+0.45	12%
P100 Cartridges (Pair)	Twin bayonet cartridges	99.97%	0%	0.09 kg	+0.7
CBRN Filter Canister	40 mm screw-on canister	100%	99.9%	0.3 kg	+0.4	10%
Surplus Filter Canister	40 mm screw-on canister	95%	80%	0.26 kg	+0.6	25%
Improvised Charcoal Filter	40 mm screw-on canister	80%	0%	0.15 kg	+0.9

A filter that loads up with particles keeps stopping them but gets harder to breathe through. A gas filter starts letting gas through near the end of its life, and a spent one stops no gas at all.

Add the filter's effort to the mask's: you struggle for breath from x1.55 and gasp from x1.85.

No filter stops carbon monoxide.

How long a filter lasts

These are the minutes a fresh filter lasts in the thickest part of each kind of bad air. An empty cell means the filter does not catch that hazard at all.

Filter	Smoke	Tear gas	Toxic gas	Rot gas	Spores	Ash	Radioactive dust
Multi-Gas Cartridges (Pair)	30 min	60 min	15 min	90 min	18 min	40 min	50 min
P100 Cartridges (Pair)	40 min	60 min			20 min	45 min	60 min
CBRN Filter Canister	45 min	120 min	30 min	180 min	30 min	60 min	80 min
Surplus Filter Canister	15 min	40 min	8 min	40 min	10 min	25 min	30 min
Improvised Charcoal Filter	10 min	20 min			6 min	12 min	15 min

Thinner air wears a filter more slowly: at half the concentration it lasts twice as long. A filter only wears while you are breathing through it in bad air.

What still reaches your lungs

For each mask and each filter that fits it, this is the share of the bad air outside that still reaches your lungs, with both in new condition. Without a mask it is 100%.

Mask	Filter	Smoke	Tear gas	Toxic gas	Rot gas	Spores	Ash	Radioactive dust
Military Gas Mask	CBRN Filter Canister	0.13%	0.1%	0.2%	0.19%	0.1%	0.1%	0.1%
Military Gas Mask	Surplus Filter Canister	8.84%	5.1%	20.08%	18.58%	5.1%	5.1%	5.1%
Military Gas Mask	Improvised Charcoal Filter	40.06%	20.08%	100%	92.01%	20.08%	20.08%	20.08%
Full-Face Respirator	CBRN Filter Canister	0.53%	0.5%	0.6%	0.59%	0.5%	0.5%	0.5%
Full-Face Respirator	Surplus Filter Canister	9.21%	5.48%	20.4%	18.91%	5.48%	5.48%	5.48%
Full-Face Respirator	Improvised Charcoal Filter	40.3%	20.4%	100%	92.04%	20.4%	20.4%	20.4%
Half-Face Respirator	Multi-Gas Cartridges (Pair)	1.77%	1.53%	2.49%	2.39%	1.53%	1.53%	1.53%
Half-Face Respirator	P100 Cartridges (Pair)	26.15%	1.53%	100%	90.15%	1.53%	1.53%	1.53%
Surplus Gas Mask	CBRN Filter Canister	7.03%	7%	7.09%	7.08%	7%	7%	7%
Surplus Gas Mask	Surplus Filter Canister	15.14%	11.65%	25.6%	24.2%	11.65%	11.65%	11.65%
Surplus Gas Mask	Improvised Charcoal Filter	44.2%	25.6%	100%	92.56%	25.6%	25.6%	25.6%
Improvised Gas Mask	CBRN Filter Canister	18.02%	18%	18.08%	18.07%	18%	18%	18%
Improvised Gas Mask	Surplus Filter Canister	25.18%	22.1%	34.4%	33.17%	22.1%	22.1%	22.1%
Improvised Gas Mask	Improvised Charcoal Filter	50.8%	34.4%	100%	93.44%	34.4%	34.4%	34.4%

Most of what gets past a good filter comes in round the seal, which is why a leaky mask with the best filter still protects poorly.

Kinds of bad air

Bad air is part particles and part gas, and a filter must stop the right one. The times are how long it takes, bare-faced in the thickest part of a cloud, before you start to cough, lose health and choke.

Spores, ash and radioactive dust do their own harm, so the table only shows what kind of filter stops them.

Only tear gas, toxic gas and rot gas sting the eyes badly enough to make you squint and blink; a half-face mask leaves your eyes bare to them.

Smoke thicker than 55% of full strength also carries carbon monoxide, which no filter stops. It can kill, it keeps hurting for a while after you reach clean air, but out in clean air it never takes you below 15% of your health.

A closed vehicle keeps out 55% of a cloud outside and a building keeps out 50%.

After you get out, you stay short of breath until the dose has cleared: sprinting costs up to 6 more stamina a second.

A thrown tear gas canister makes a cloud that grows from 3 m to 11 m across its radius in 12 seconds and lasts 75 seconds.