This is supposed to be a general overview of the subject of respirators, aimed at collectors, airsoft players, and preppers.
A respirator is a device worn on the face to filter out hazardous gases or particles, or to provide unfiltered supplied air (usually through rebreathing, or compressed air)
First World War
Gas masks were first developed during the First World War, as a response to the use of crude chemical weapons. At first, these masks were quite basic, often consisting of pads over the mouth and nose and fabric hoods, but later development produced respirators more resembling modern masks. The Germans pioneered the use of corrective inserts for soldiers who needed glasses.
Various chemical weapons were developed during the first world war. Initially, lachrymatory agents (riot agents) were used, followed by pulmonary agents (Chlorine and Phosgene), blistering agents (Mustard gas), and blood agents (Hydrogen Cyanide)
Second World War
The Second World War saw further developments in gas mask design. Most masks were made from latex, and some specialised masks had integrated microphones, or voice diaphragms, thin membranes which vibrate to make the user's voice clearer. In the United Kingdom, gas masks were issued to civilians due to widespread fear that the Germans would use chemical weapons against them.
Germany developed a new type of chemical weapon, nerve agents, producing Tabun (1936), Sarin (1939), Cyclosarin, and Soman (1944). NATO and the Warsaw Pact subsequently adopted Sarin as a standard chemical weapon.
The Japanese empire experimented with various diseases on thousands of Chinese prisoners, and attacked Chinese civilians with anthrax and the bubonic plague.
During the cold war, both power blocs fielded nuclear, biological and chemical weapons, and the defensive emphasis consequently changed to reflect this. At first, these three threats were referred to as ABC (Atomic, biological, chemical), but this later changed to NBC (Nuclear, biological, chemical).
Filter canister threads were standardised during the cold war, with NATO and the Warsaw Pact both adopting 40mm threads with differing pitches. Military forces were widely issued with protective clothing, personal decontamination equipment, and antidotes for nerve agents.
NATO masks progressed steadily during this period, with the general issue US M17 featuring a voice diaphragm, and a drinking system. NATO masks in general featured plastic, often triangular lenses. The east bloc was slower to update its mask designs, most retaining glass lenses, with only some featuring voice diaphragms, and only very late Soviet masks featuring drinking systems.
While the threat of widespread use of weapons of mass destruction receded with the end of the cold war, rogue states and terrorist organisations continue to pose a threat. The increased threat of so-called "dirty bombs" prompted the NBC acronym to be updated to CBRN (Chemical, Biological, Radiological, Nuclear).
Modern respirators universally feature peripheral seals, orinasal cups, drinking systems and voice diaphragms. Most are made of Butyl (a synthetic rubber), which offers better protection, and doesn't irritate the skin of users with a latex allergy. Some modern masks have moved away from the traditional filter canister design, and instead use dual cartridges, with the inlets sealing during filter changes.