This article is about a concept, not a mask.
This article has been written about something that is not a specific model of mask, but a concept relating to CBRN warfare or the engineering behind gas masks.
The subject of filter safety can be a controversial topic between collectors, and is often the subject of extended debate. This article is intended to provide a general overview.
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Failure to remove caps from filter intakes will render the user unable to breathe in a mask. This represents a risk more to inexperienced or incapacitated users than collectors.
Older filters often contain asbestos, it is now known that prolonged inhalation of asbestos fibers can cause serious and fatal illnesses including lung cancer, mesothelioma and asbestosis (a type of pneumoconiosis). From the 1970s onwards, its dangers became well publicised, and its use declined sharply, being ultimately outright banned in many countries. No modern filters are known to contain asbestos.
Modern filters may still contain chromium, used as a catalyst. While less dangerous than asbestos, extended exposure can increase the likelihood that the user will contract cancer.
No filters are known to contain lead, but the paint on older filters, and more recent filters from countries with less strict standards may contain lead. This does not pose a risk for general use of the filter, but extensive chipping, or deliberate stripping of the paint could allow the paint to be inhaled or ingested.
Older filters may not protect you from Biological, Chemical, or Nuclear attacks. While the masks themselves have no real expiration date, provided that their seals and valves are not compromised, the filters lose effectiveness with time.
Tips for Identifying Russian filtersEdit
Here it is an example of a cartridge inscriptions, this is a DPG-3 GOST Russian cartridge.
This next information is a translation from a Russian website, so it may be not 100% correct, please be advised.
On the side surface of the additional cartridge DPG-3 is marked as follows:
"DPG-3" - the name of the product;
"M" in an equilateral triangle - the code of the manufacturer (JSC "sorbent");
«II» - quarter of production (in this case, additional cartridge ACF-3 is made in the second quarter);
"12" - the year of manufacture (in this case, additional cartridge made in 2012);
"11" - batch number.
Labelling must be clear, no correction, the vagueness and traces of ink are not allowed.At the bottom of the additional cartridge DPG-3 is marked as follows.
Then look at the most common ways to fake (falsification) additional cartridge ACF-3.
The figures below the shows the top of an additional cartridge ACF-3 missing.
Not just a part against counterfeiting marking - missing all markings:
- Lack of a ring ridge;
- The lack of radial "ribs";
- Lack of manufacturer's name;
- Lack of year of manufacture.
Known dangerous filtersEdit
U.S. C2 40 MM 
S-10 (Gasmask) OEM 40 MM Filter (Only those designated as "L12A1" are dangerous)
M13a2 filters for the M17 (contain chromium) earlier models may be safe
British civil filters from the WW2 era (contain blue asbestos and arsnic)
M2-10a1-06 filters (contain asbestos)
Some variants of the GP-5 filter dangerous years unknown (contain asbestos)
German VM-37 and VM-40 filters (contain asbestos)