Gas masks, also known as “air-purifying respirators” (APRs), are defined by the regulation as devices designed for use during entry into atmospheres not immediately dangerous to life or health or escape only from hazardous atmospheres containing adequate oxygen to support life.
Personal protective equipment (class 3 PPE) covers the respiratory tracts (nose and mouth) as well as the eyes, allowing protection against certain toxic, irritating, and/or corrosive substances.
Using personal protective equipment (PPE) is one of the safety measures, supplementary to control measures, in providing protection to the employees. Despite the use of PPE is often considered a passive way to control risk, with thoughtful management, a very proactive PPE program can be developed.
These consist of a full-mask facepiece, which covers the eyes, nose, and mouth, this respirator includes a facepiece or mask, and a filter/cartridge connected either directly or via a non-kink flexible hose to a canister containing a granular sorbent.
The cartridge may have a filter to remove particles (such as a biological weapon), charcoal (to remove certain chemicals), both, or other parts. When the user inhales, the air is pulled through the filter.
It should be noted that the filter, cartridge, or canister has limited capacity for the specific contaminant. This limits the duration of protection offered by the respirator and its use
in an environment with high contaminant concentrations. A chemical cartridge or canister has a limited life. It should be replaced if the expiry date is reached.
Gas masks are also known as “air-purifying respirators” because they filter or clean chemical gases and possibly particles out of the air as you breathe. Straps secure the facepiece to the head.
Gas Masks are effective only if used with the correct cartridge or filter (these terms are often used interchangeably) for a particular biological or chemical substance. Selecting the proper filter can be a complicated process. There are cartridges available that protect against more than one hazard, but there is no “all-in-one” filter that protects against all substances. You need to know what hazards you will face being certain you are choosing the right filters.
Limitations and restrictions of use provided with the respirator must be strictly followed. If your mask does not make a tight seal around your face when you inhale, you may breathe contaminated air that leaks around the edges of the face seal. Anything that prevents the face mask from fitting tightly against your face, such as a beard or long sideburns, may cause leakage. Some respirators come in different styles and sizes and fit different people differently because people’s faces have different shapes. You also need the training to know how to correctly put the mask on and wear it correctly.
Current gas masks are composed of a rubber or silicone skirt that guarantees perfect adherence to the face; they also have tabs and buckles to secure the gas mask behind the head.
They are also equipped with a large clear visor made of polycarbonate or laminated glass that offers wide visibility.
Inside there is a second mask that covers the nose-mouth area. In this internal mask, there are two openings: one for inhalation and one for exhalation, provided with special valves to condition the airflow. The inhalation valve is connected to a filter that uses properly treated activated carbon-based substances to filter and fix harmful gases, while the exhalation valve expels the breathed air without making the viewer fog up.
Types of gas masks are:
a) Front-mounted or back-mounted – A gas mask which consists of a full facepiece, a breathing tube, a canister at the back or front, a canister harness, and associated connections.
b) Chin-style gas mask – A gas mask, which consists of a full facepiece, a canister that is usually attached to the facepiece, and associated connections.
c) Escape gas masks – A gas mask designed for use during escape only from hazardous atmospheres, which consists of a facepiece or mouthpiece, and associated connections. This type of mask often comes in the form of a half mask, which provides no eye protection.
A gas mask is designed to protect the face and lungs against noxious gases and fumes, chemical agents, and biological substances as in warfare or terror attacks or in certain industrial environments. The gas mask includes a cartridge or canister containing activated carbon and/or chemicals to remove dangerous gas and vapor contaminants. A particulate filter may be attached to the cartridge or canister. Gas masks are also described by the types of gases or vapors against which they are designed to protect as follows:
The regulation specifies canister bench tests to qualify a gas mask. For each gas mask type and canister type, the regulation specifies a challenge gas or vapor, a feed concentration, a flow rate, a specified number of tests, a maximum allowable penetration, and a minimum service life. As an example, Table 8.17, on page 363 below compares specific test requirements for ammonia as the challenge gas. The regulation also specifies particulate tests for those gas masks containing a particulate filter. In this regard, the gas mask becomes like a non-powered air-purifying particulate arrestor (NPAPPR) and is subject to the testing protocol as discussed in Section 8.4.1.4.