A self-contained breathing apparatus ( SCBA ) is sometimes referred to as air compressor ( CABA ), or just a breathing apparatus ( BA ), is a tool used by rescue workers, firefighters, and others to provide deep breathing air harmful to life or health atmosphere (IDLH). When not used underwater, they are sometimes called industrial respiration sets . The term standalone means that the respiratory set does not depend on the remote supply (eg, over a long interval). If designed for underwater use, it is called SCUBA ( self-contained underwater breathing apparatus ).
SCBA typically has three main components: a high-pressure tank (eg, 2,216-5,500 psi (15,280 to 37,920 kPa), about 150 to 374 atmospheres), pressure regulator, and inhalation connection (mouthpiece, mouth mask or face mask), connected together and mounted to the carrier frame.
Self-contained breathing apparatus can fall into two different categories. This is an open circuit and closed circuit.
Video Self-contained breathing apparatus
SCBA enclosed circuit
Closed circuit type filters, supplements, and gas recirculation are exhaled: see rebreather for more information. This is used when the supply of respiratory gas is needed in longer durations, such as in mine rescue and in long tunnels, and through channels that are too narrow for large open air cylinders. Before the open circuit SCBA was developed, most industrial respirators were rebreathers, such as Siebe Gorman Proto, Siebe Gorman Savox, or Siebe Gorman Salvus. Examples of modern rebreather SCBAs are SEFA. Underwater rebreathers have the advantage of not releasing bubbles, making it more difficult to detect the divers involved in covert operations (see frog man).
Maps Self-contained breathing apparatus
Open circuit
- For an open circuit underwater open circuit see Scuba set # Types.
The open circuit industry breathing circuit is filled with filtered and compressed air, rather than pure oxygen. A typical open circuit system has two regulators; the first stage to reduce the air pressure to allow it to be brought into the mask, and the second-stage regulator to reduce it further to levels just above standard atmospheric pressure. The air is then fed to the mask through the demand valve (active only during inhalation) or continuous positive pressure valve (providing constant airflow to the mask).
SCBA open-circuit or SCBA fire extinguishers have full masks, regulators, air cylinders, cylinder pressure gauges, remote pressure gauges (sometimes with integrated PASS devices), and harness with adjustable shoulder straps and belts that allow them to wear on back. Air cylinders usually come in one of three standard sizes: 4 liters, 6 liters, or 6.8 liters. The duration of the cylinder can be calculated by this formula: volume (in liters) * pressure (in bars)/40 - 10 in minutes (10 minus to provide safety margin), so the 6-liter, 300bar cylinder is 6 X 300/40 - 10 = 35 minutes duration of work. The relative fitness levels, and especially the wearer's level of deployment, often result in the actual time variations that SCBA can use to provide air, often reducing the working time by 25% to 50%.
Air cylinders are made of aluminum, steel, or composite construction (usually wrapped in carbon fiber.) The composite cylinder is the lightest and therefore preferred by the fire department (UK: fire and rescue service previously called fire brigade), but they also have shortest lifespan and must be excluded from service after 15 years. Air cylinders should be tested hydrostatically every 5 years. During extended operation, empty air cylinders can be quickly replaced with fresh ones and then refilled from larger tanks in a cascade storage system or from air compressors brought to the scene.
Fullface Mask
Full face masks of breathing apparatus designed for use out of water are sometimes designed in ways that make them unsuitable for scuba diving, although some may allow a very shallow emergency landing:
- The seal on the edge of the mask is a wide tube with thin, flexible walls that surround the edge of the mask, full of air at atmospheric pressure. On the surface it pushes to the edge of the wearer's face, causing a tight seal despite slight variations in head shape. At some deeper foot pressure (under water or in caisson) this tube collapses, destroys the seal and makes a mask leak.
- Curved windows under water will severely damage the image by refraction.
The mask can have a large fullface window, or small eye window.
The mask may have small inside orinasal respiratory mask inside, reducing breathing breathing space.
The mask can also combine two-way radio communicators.
- See also full face diving mask
Some old industrial rebreathers (eg, Siebe Gorman Proto) have a funnel and attached a noseclip instead.
Positive pressure (prevents leakage in)
Open circuit SCBAs use "positive pressure" or "negative pressure" operation.
- A "negative pressure" SCBA can be used with a fullface mask type that can be used as a gasmask (with a filter canister on the facepiece airspace) or with an open circuit circuit connected to the air intake. Air is sent to the wearer as he inhales, or in other words, reduces the pressure in the mask to less than outside pressure, hence the name "negative pressure". This limitation is obvious, because any leak in the device or interface between the mask and the wearer's face (caused eg by small facial skin wrinkles) will reduce the protection offered.
- "Positive pressure" SCBA overcomes this limitation. With careful design, the device is set to maintain a small pressure that exceeds the surrounding air pressure inside the face cover. Although the pressure decreases when the wearer breathes, it always maintains a higher pressure inside the mask than outside the mask. So, even if the mask is leaking a bit, there is a clean airflow out of the device, automatically preventing the leakage into in most circumstances. Although the performance of both types of SCBA may be similar under optimal conditions, this "safe failure" behavior makes SCBA "positive pressure" preferred for most applications. Since there is usually no penalty for using air in positive pressure, the older "Negative Pressure" type is, in many cases, obsolete and only visible with older equipment. However some users refuse to use this technology because if there is damage or loss of face cover then air will be released uncontrollably. The leakage rate can be so high that a fully loaded SCBA will be drained in less than three minutes, a problem that does not occur with the SCBA system "negative pressure".
Usage type
There are two main application areas for SCBA: fire fighting; and industrial usage. The third use that is now being used is medical; for example, the American National Institutes of Health prescribes the use of SCBA for medical staff during ebola treatment.
For fire fighting, the design emphasis is on heat resistance and fire over charge. SCBAs designed for fire suppression tend to be expensive because of exotic materials used to provide fire resistance and to a lesser extent, to reduce heavy penalties on firefighters. In addition, modern firefighter SCBAs incorporate PASS (personal signature security systems) or ADSU (automatic distress signal units) into their designs. These units emit a distinctive high-pitched alarm tone to help find the fire extinguisher in trouble by automatically activating if the movement is not felt for a certain period of time (usually between 15 and 30 seconds), also allows for manual activation if required. In the use of fire extinguishers, the layout of this breathing set should not interfere with the ability to bring the rescued person on the shoulders of the fire department.
Other major applications are for industrial users of various types. Historically, mining is an important area, and in Europe it is still reflected in the limitations of use in SCBA construction of metals that can cause sparks. Other important users are petrochemical, chemical and nuclear industries. The design emphasis for industrial users depends on appropriate applications and extends from the critical down-to-end, to the most severe environments where SCBA is one part of an integrated protective environment that includes tight gas settings for whole body protection and ease of decontamination. Industrial users will often be air supplied through the airways, and only carry compressed air for the purpose of escape or decontamination.
Security specifications
In the United States and Canada, the SCBA used in firefighting must comply with guidelines established by the National Fire Protection Association, NFPA Standard 1981. If SCBA is labeled "1981 NFPA compliant", it is designed for firefighters. The standard version is currently published in 2013. These standards are revised every five years. Similarly, the National Institute for Occupational Safety and Health (NIOSH) has a certification program for SCBA that is intended for use in chemical, biological, radiological, and nuclear (CBRN) environments. See NIOSH Approved SCBAs.
Any SCBA provided for use in Europe must comply with the requirements of the Personal Protection Equipment Regulations (89/686/EEC). In practice this usually means that SCBA must comply with the requirements of the European Standard EN 137: 2006. This includes detailed requirements for SCBA performance, required tagging, and information to be provided to users. Two SCBA classes are recognized, Type 1 for industrial use and Type 2 for fire fighting. Any SCBA that complies with these standards will be verified to operate reliably and protect users from -30 Â ° C to 60 Â ° C under various heavy operational simulation conditions.
Royal Australian Navy uses an open circuit of compressed air breathing apparatus (OCCABA), a positive pressure breathing apparatus, a backpack style, for a fire-fighting role.
Effect of temperature on pressure gauge readings
The pressure of the pressure gauge is shown to change with ambient temperature. As the temperature decreases, the pressure inside the cylinder decreases. The relationship between temperature and gas pressure is determined by the formula PV Ã, = nRT . (See Universal gas constant.) What is very important to understand from the formula is that the temperature is in kelvin, not the degree of Fahrenheit. Consider the freezing point of water at 32 ° F (0 ° C, 273.15 ° K) and compare with 96 ° F (35.6 ° C or 308.71 ° K) Normal human body temperature is 37  ° C). While 96 is arithmetically three times 32, the temperature difference from a scientific point of view is not threefold. Instead of comparing 32Ã,  ° F to 96Ã,  ° F, temperatures of 273.15Ã,  ° K and 308,71Ã, K should be compared. A scientifically valid temperature change from 32 to 96 ° F (0 to 36 ° C) is by a factor of 1.13 (308.71 K/273.15 K), not 3. If the air cylinder is pressurized to 4,500 psi at temperature 96Ã,  ° F and then the temperature drops to 32Ã,  ° F, the pressure gauge will show 4,000 psi (4,500/1.13). Expressed differently, a temperature drop of 10  ° F (5.5  ° C) causes a pressure drop of about 82 psi. Failure to accurately account for the effect of temperature on a pressure reading may result in a full air bottle, which in turn may cause a firefighter to run out of air prematurely.
Type
Among the leading SCBA manufacturers for North American fire services are:
- Scott's Security
- Avon-ISI
- MSA Fire
- Draeger
- Survivair
- Interspiro
- ISI (International Security Instrument).
Among the leading SCBA manufacturers for the European fire service and industrial security:
- Honeywell Security Products
- Health and Security Scott
- Spasciani
- Interspiro
- MSA
- Draeger
Siebe Gorman produces these open-circuit SCBA units:
- Airmaster MK 1 (blue back plate)
- Airmaster MK 2 (chrome plated back plate)
- Fire Brigade
- Special for the armed forces
Also known as
In Australia, different fire-fighting agencies refer to SCBA with various acronyms in common terms. As an example:
- In South Australia, both the State Fire Department and the Metropolitan Fire Service refer to SCBA as "CABA" or "compressed air breathing apparatus" during training and in the field they refer to SCBA simply. BA or breathing apparatus . The New South Wales Rural Fire Service follows the same principle as South Australia
- The Western Australia Brigade Fire and Emergency Service Authority, the New South Wales Fire Brigade, and the Queensland Fire and Rescue Service call it BA, breathing apparatus .
All of these terms mean the same type of open circuit equipment.
In New Zealand, SCBA is generally referred to by the New Zealand Fire Service personnel as BA, respirator .
Unofficial names include air packages, air tanks or just packs, most of which are used in firefighting such as in "fired" firefighters.
See also
- Glossary of the term firefighter
- Oxygen mask
- Gas mask
- PASS devices (private alert security systems), also known as ADSU (automatic distress signal units) - which are often integrated into SCBA systems
- SCUBA - a standalone underwater breathing tool
- STAS - short term air supply for self-preservation
- Jean-FranÃÆ'§ois PilÃÆ' Â ¢ tre de Rozier
Note
References
- IFSTA (2008). "Fire 5th Edition and Fire Operations 5th Edition"
External links
- This reference is related to NIOSH-certified SCBA with chemical, biological, radiological and nuclear protection (CBRN) (SC/PD/CBRN):
- The CBBA CBBA user guide and the approved CBBA CBBA list
- Development and publication of CBRN SCBA standards leading to the first NIOSH Certified SCBA with CBRN protection offered by US DHHS/CDC/NIOSH/NPPTL on June 3, 2002
- Figure 2-cylinder open circuit SCBA
- Death Savers at the Underground Mine
- Literature
- Learn the physiological effects of using breathing apparatus by RG Love and others. Research Report of Vocational Research Institute TM/94/05
Source of the article : Wikipedia
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