A supplied-air respirator (SAR) or air-line respirator is a breathing apparatus used in places where the ambient air may not be safe to breathe. It uses an air hose to supply air from outside the danger zone. It is similar to a

self-contained breathing apparatus A self-contained breathing apparatus (SCBA), sometimes referred to as a compressed air breathing apparatus (CABA) or simply breathing apparatus (BA), is a device worn to provide breathable air in an atmosphere that is immediately dangerous to ...

(SCBA), except that SCBA users carry their air with them in high pressure cylinders, while SAR users get it from a remote stationary air supply connected to them by a hose.

Description

SARs are lightweight, but tether the user. Unlike SCBAs, the worker will not run out of air when the tank they carry is empty. They can therefore be used for longer continuous work periods. The mask end of a SAR is generally lower-maintenance than an SCBA, but the air compressors or tanks at the other end of the hose require monitoring and maintenance. It is important that they deliver good air; contaminants (which may also be introduced by faulty operation of the machinery) can be dangerous. If the air-supply line is cut or pinched shut, the user will not have any air to breathe. SAR users therefore often carry a small backup air tank (called an ''auxiliary escape cylinder''). In an emergency, they can switch to using this supply, which should last long enough for them to escape the dangerous area. This backup bottle is required in some jurisdictions. Other regulations also apply. Users of SARs must generally be given hands-on training with the specific model they are to use. SARs may be either constant-flow or pressure-demand respirators. Constant-flow respirators supply a steady stream of air, some of which escapes from the wearer end unbreathed. Pressure-demand respirators supply air only when the pressure in the wearer's mask drops (that is, when they inhale). This saves air but allows more inwards leakage. Pressure-demand respirators can only be used with a sealed elastomeric mask, not with a loose-fitting hood (like those used in

powered air-purifying respirator A powered air-purifying respirator (PAPR) is a type of respirator used to safeguard workers against contaminated air. PAPRs consist of a headgear-and-fan assembly that takes ambient air contaminated with one or more type of pollutant or pathoge ...

s) or helmet (used in construction). Hoods may be made of

Tyvek Tyvek () is a brand of synthetic flashspun high-density polyethylene fibers. The name "Tyvek" is a registered trademark of the American multinational chemical company DuPont, which discovered and commercialized Tyvek in the late 1950s and early ...

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...

, or

polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins and ...

Use

According to the NIOSH Respirator Selection Logic, SARs with an auxiliary SCBA are recommended for

oxygen-deficient atmosphere Inert gas asphyxiation is a form of asphyxiation which results from breathing a physiologically inert gas in the absence of oxygen, or a low amount of oxygen, rather than atmospheric air (which is composed largely of nitrogen and oxygen). Examples ...

s, atmospheres that are

immediately dangerous to life or health The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent advers ...

, and unknown atmospheres, all of which are conditions that air-purifying respirators such as

N95 mask An N95 filtering facepiece respirator, commonly abbreviated N95 respirator, is a particulate-filtering facepiece respirator that meets the U.S. National Institute for Occupational Safety and Health (NIOSH) N95 classification of air filtratio ...

s do not protect against. SARs without an auxiliary SCBA may also be used in conditions where an

air-purifying respirator A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including fumes, vapours, gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respir ...

may be used, and have the benefit of a higher range of assigned protection factors (APF). Air-purifying respirators have APFs in the range 5–50 while SARs are in the range 25–2000, and full-facepiece pressure-demand SARs with an auxiliary pressure-demand SCBA have an APF of 10,000. For substances hazardous to the eyes, a respirator equipped with a full facepiece, helmet, or hood is recommended. SARs are not effective during

firefighting Firefighting is the act of extinguishing or preventing the spread of unwanted fires from threatening human lives and destroying property and the environment. A person who engages in firefighting is known as a firefighter. Firefighters typically ...

, for which a SCBA is recommended instead.

References

External links

* {{Breathing apparatus, industrial Industrial breathing sets Functional masks Respirators