A respirator is a device for individual protection of respiratory organs of man from dust and harmful substances in the atmosphere. The simplest type of respirator is cotton-gauze dressing that is used by medical personnel and population protection from the droplet infection. Respirators can be divided into two groups: insulating and filtering. In the production of respirators are used in conditions of high dust content and gas air pollution (mines, ore - dressing plants, in open cut mining of ore, coal, at presence in the air of radioactive aerosols and other).

respirator SC - 5
Fig. 1. Insulating respirator SC - 5:
1 - oxygen cylinder;
2 - an host;
3 - valve manual feed (bypass);
4 - excessive valve;
5 - dyhatelnye valve;
6 - expiratory valve;
7 - a breathing bag;
8 - regenerative cartridge;
9 - reducer.

Isolating respirators are used at low (less than 16%) content of oxygen in the air, as well as in cases, when the concentration of contaminants in the air are very high and the use of filtering respirators is not reliable (emergency operation). In Fig. 1 shows the scheme of insulating respirator SK-5. When exhaling the air from the lungs passes through expiratory valve 6 and goes on corrugated tube inside the breathing bag 7 in regenerative cartridge 8 containing chemical absorber of carbon dioxide. Thus treated air through a broad neck is sent to a breathing bag 7, where, when breathing through dyhatelnye valve 5 goes into the lungs. Spent when breathing oxygen is replenished from an oxygen cylinder 1, having an node 2, passing through the gear 9. If the oxygen supply is insufficient, it is additionally serves manually using valve manual feed (bypass) 3. Excessive amount of air congestion in the bag is removed through excessive valve 4.
In practice, there are isolating respirators ALAC-2, ALAC-2M, "Ural-1" and other disadvantages of isolating respirators should include a lot of weight and dimensions, the complexity of the design and use. In case of damage to the metal housing that contains the associated oxygen (in the form of peroxides), he may cause fire or explosion.
By isolating respirators are also an airline respirator. They are used to gas rescue stations and municipal economy (sandblasting). The range of hose respirators limited by the length and weight of the hose. In hose respirators with the forced air is continuously washed by the person running fresh stream, thanks to high ambient temperature is transferred easily.
In cases when you cannot avoid air pollution by dust, the only way to respiratory protection is the application of the dust filter respirator.
One of the main advantages of the filter respirator is its ease and portability, and a low breathing resistance. He 10-15 times lighter than isolating breathing apparatus of compressed oxygen. Filter respirator consists of front and filter for the delay dust. The front part of a respirator may be in the form of a helmet-masks or masks. Obturator must preserve the integrity of the masks, to fit tightly to the face and not to put pressure on the skin. When protecting the head, neck and face from the dust respirators are used in combination with a hood. In modern respirators widely used as a filter filter synthetic fabric type FRR of ultra-thin plastic fibers. In recent years, new, improved design of respirators single and multiple actions. Using modern filter materials made it possible to reduce the weight of the majority of structures and to increase the coefficient of palisadian for small start breathing resistance. The appearance of some respirators are shown in Fig. 2. The best designs dust respirators should be considered SB-1 "Lepestok-200" and "Astra-2". Well established respirator U-2K when working with the application of powdered pesticides.
When working in the conditions of air pollution with harmful gases instead dust filtering respirators should be used masks (see).respirators

Fig. 2. Anti-dust respirators:
1 - SB-1 "Lepestok-40"; 2 - "Astra-4"; 3-Y-2K; 4 - f-t; 5 - RPU-22 D; 6 NIGRI-1.