Self-Contained Breathing Apparatus (SCBA)
A self-contained breathing apparatus (SCBA) usually consists of a facepiece connected by a hose and a regulator to an air source (compressed air, compressed oxygen, or an oxygen-generating chemical) carried by the wearer.
Drager SCBA Specifications
Only positive-pressure SCBAs are recommended for entry into atmospheres immediately dangerous to life and health (IDLH). SCBAs offer protection against most types and levels of airborne contaminants. However, the duration of the air supply is an important planning factor in SCBA use (see PPE use later in this course). This is limited by the amount of air carried and its rate of consumption.
Also, SCBAs are bulky and heavy. Thus they increase the likelihood of heat stress and may impair movement in confined spaces. Generally, only workers handling hazardous materials or operating in contaminated zones require SCBAs.
Under MSHA regulations in 30 CFR Part 11.70(a), SCBAs may be approved for:
- escape, only, or
- for both entry into and escape from a hazardous atmosphere.
Escape-only SCBAs are frequently continuous-flow devices with hoods which can be donned to provide immediate emergency protection. Employers should provide and ensure employees carry an escape SCBA where such emergency protection may be necessary.
Entry-and-escape SCBAs give workers untethered access to nearly all portions of the worksite, but decrease worker mobility, particularly in confined areas, due to both the bulk and weight of the units. Their use is particularly advisable when dealing with unidentified and unquantified airborne contaminants.
There are two types of entry-and-escape SCBAs: Open circuit and closed circuit.
- Open-circuit: In an open-circuit SCBA, air is exhaled directly into the ambient atmosphere.
- Closed-circuit: In a closed-circuit SCBA, exhaled air is recycled by removing the carbon dioxide with an alkaline scrubber and by replenishing the consumed oxygen with oxygen from a solid, liquid, or gaseous source.
All compressed breathing gas cylinders must meet minimum U.S. Department of Transportation (USDOT) requirements for interstate shipment. All compressed air, compressed oxygen, liquid air, and liquid oxygen used for respiration must be of high purity and meet all requirements of OSHA 29 CFR Part 1910.134(d). Also, breathing air must meet or exceed the requirements of Grade D breathing air as specified in the Compressed Gas Association Pamphlet G-7.1 and ANSI Z86.1-1973.
Knowledge Check Choose the best answer for the question.
1-7. What type of SCBAs are recommended for entry into atmospheres immediately dangerous to life and health (IDLH)?
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