Self-contained breathing apparatus

From Wikipedia, the free encyclopedia

1 Closed-circuit SCBAs
2 Open-circuit
3 Also known as
4 See also

“SCBA” redirects here. For other uses, see SCBA (disambiguation).

A self contained breathing apparatus, or SCBA is a device worn by rescue workers, firefighters, and others to provide breathable air in a hostile environment. When not used underwater, they are sometimes called industrial breathing sets. The term "self-contained" differentiates SCBA from other apparatus connected to a remote supply by a long hose. If designed for use under water, it is called SCUBA, or self-contained underwater breathing apparatus.

An SCBA typically has three main components: a high-pressure tank (e.g., 2200 psi to 4500 psi), a pressure regulator, and an inhalation connection (mouthpiece, mouth mask or face mask), connected together and mounted to a carrying frame.

There are two kinds of SCBA: open circuit and closed circuit.

[edit] Closed-circuit SCBAs

Siebe Gorman Savox in a coalmining museum

The closed-circuit type filters, supplements, and recirculates exhaled gas: see rebreather for more information. It is used when a longer-duration supply of breathing gas is needed, such as in mine rescue and in long tunnels, and going through passages too narrow for a big open-circuit air cylinder. Before open-circuit SCBA's were developed, most industrial breathing sets were rebreathers, such as:-

Examples of modern rebreather SCBAs are

SEFA
A set made by Draeger.
Biopak (1-hour and 4-hour versions) [1]

For rebreathers used underwater, where they have the advantage of not releasing tell-tale bubbles, making it more difficult to detect divers involved in covert operations, see frogman.

[edit] Open-circuit

A Firefighter wearing an SCBA Breating mask with a Nomex hood on. This mask was designed for MSA brand air packs.

A truck mounted SCBA pack.

Open-circuit industrial breathing sets are filled with filtered, compressed air, the same air we breathe normally. The compressed air passes through a regulator, is inhaled by the user, then exhaled out of the system, quickly depleting the supply of air. Most modern SCBAs are open-circuit.

An open-circuit rescue or firefighter SCBA has a full-face mask, regulator, air cylinder, cylinder pressure gauge, and a harness with adjustable shoulder straps and waist belt which lets it be worn on the back. The air cylinder usually comes in three sizes a 30 minute tank, 45 minute tank, and a 60 minute tank. These tanks however usually do not last the full duration depending on the exertion and fitness of the wearer, from personal experience a 30 minute tank can last as little as 10-15 minutes under full exertion.

SCBA apparatus with a PASS device attached.

Air cylinders are made of aluminum, steel, or of a composite construction (usually Carbon-Fiber wrapped.) The composite cylinders are the lightest in weight and are therefore preferred by fire departments (UK: fire brigades), but they also have the shortest lifespan and must be taken out of service after 15 years. Air cylinders must be hydrostatically tested every 3 years for composite cylinders, and every 5 years for metal cylinders. During extended operations, empty air cylinders can be quickly replaced with fresh ones and then refilled from larger tanks in a cascade system or from an air compressor brought to the scene.

Commonly an SCBA will be of the "positive pressure" type, which supplies a slight steady stream of air to stop toxic fumes or smoke from leaking into the mask. Not all SCBAs are positive pressure; others are of the "demand" type, which only supply air on demand (i.e., when the regulator senses the user inhaling). All fire departments and those working in toxic environments need to use the positive pressure SCBA for safety reasons.

As SCBA technology has evolved, different models have evolved for firefighting, versus those designed for where the set does not need to be heat resistant, such as in mining. In the USA, SCBAs used in firefighting must meet guidelines established by the National Fire Protection Association, NFPA Standard 1981. If an SCBA is labeled as "1981 NFPA compliant", it is designed for firefighting. The current version of the standard was published in 2002. Similarly, the National Institute for Occupational Safety and Health (NIOSH) has a certification program for SCBA that are intended to be used in chemical, biological, radiological, and nuclear (CBRN) environments. See NIOSH Approved SCBAs.

[edit] Also known as

In Australia different firefighting agencies refer to SCBA by different acronyms in general terms. For example, the New South Wales Rural Fire Service refers to SCBA as CABA, Compressed Air Breathing Apparatus, and the New South Wales Fire Brigades refers to it as BA, Breathing Apparatus. Despite the different names, SCBA, CABA and BA here all refer to the same type of Open-circuit equipment.

Scott Aviation, a company with World War II experience in providing oxygen systems for military air crews, was the first to manufacturer Open Circuit Self Contained Breathing Apparatus on a large scale for the fire service, utilizing compressed air since oxygen would be too hazardous for this use. Scott, now the Scott Health& Safety division of Tyco International (2006), coined the term AirPak® for its product in the 1950s and owns that term as a Registered Trademark in the U.S. However, the word "airpack" has come into generic use as a synonym for SCBA, much to the Scott company's consternation.

Among the leading manufacturers of SCBA for the USA fire service are: Scott, Survivair, MSA, Interspiro, ISI (International Safety Instruments) and Draeger.

Siebe Gorman produced a number of SCBA units which were as follows - Airmaster MK 1 (blue back plate); Airmaster MK 2 (chrome plated back plate); Firefighter; along with other specials for the armed forces