Self-contained breathing apparatus

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Self-contained breathing apparatus
TFS SCBA gear.jpg
Other name(s)SCBA, compressed air breathing apparatus, breathing apparatus
Regulated by National Institute for Occupational Safety and Health, National Fire Protection Association
Regulation 42 CFR 84, EN 137, NFPA 1981
NIOSH scheduleTC-13F

A self-contained breathing apparatus (SCBA) is a respirator worn to provide an autonomous supply of breathable gas in an atmosphere that is immediately dangerous to life or health from a gas cylinder. [1] They are typically used in firefighting and industry. The term self-contained means that the SCBA is not dependent on a remote supply of breathing gas (e.g., through a long hose). They are sometimes called industrial breathing sets. Some types are also referred to as a compressed air breathing apparatus (CABA) or simply breathing apparatus (BA). Unofficial names include air pack, air tank, oxygen cylinder or simply pack, terms used mostly in firefighting. If designed for use under water, it is also known as a scuba set (self-contained underwater breathing apparatus).

Contents

An open circuit SCBA typically has three main components: a high-pressure gas storage cylinder, (e.g., 2,216 to 5,500  psi (15,280 to 37,920  kPa ), about 150 to 374 atmospheres), a pressure regulator, and a respiratory interface, which may be a mouthpiece, half mask or full-face mask, assembled and mounted on a framed carrying harness. [2]

A self-contained breathing apparatus may fall into one of three categories: open-circuit, closed-circuit, [3] or continuous-flow. [4]

History

As the fire service began to develop throughout the early 1800s, it became increasingly apparent that firefighters needed protection from the hazardous smoke and toxic gasses that were present when fighting fires.[ according to whom? ] The earliest attempts at this included firefighters growing out long beards, dipping them in water, and then biting down on the beard while breathing through their mouth. The theory behind this was that the wet beard would act as some sort of filter for the smoke. Other early attempts included the French designed "Apparatus Aldini" which was an asbestos and woven wire mask which attempted to provide the user with a small amount of trapped clean air to breath and an English designed closed helmet that pumped clean air across a pane of glass to reduce breathing condensation. [5]

The first real attempt at an SCBA came from a man named James Braidwood. Around 1825, he invented[ failed verification ] a mask that was connected to a long hose which was then connected to a fire engine. The firefighter would then go inside the building connected to fresh air via the air line. A whistle was also attached to the mask for communications. This could be considered to be one of the first attempts of a PASS or Personal Alert Safety System device.[ failed verification ] [5]

Paul Hashagan also notes that, in 1863, A. Lacour developed and patented the "improved breathing apparatus". This system provided air to the wearer from two canvas and rubber balloon-like bags which were carried on the wearer's back. A pair of bellows would then allow the wearer to pump air to a mouthpiece. The firefighter would also wear goggles and a nose plug to provide further protection from the smoke and heat. [5]

Throughout the 1800s, other SCBA-like devices were developed by various people[ failed verification ] including a closed-circuit rebreather designed by Bernhard Draeger. The closed circuit system developed by him would not only be used by many fire departments, but also was one of the first working SCUBA systems.[ inconsistent ] [6] Other devices included the Gibbs which was approved for use in 1920 and was developed by MSA [7] and the Proto, which was developed by a German named Siebe Gorman. [8]

Close to the mid 1900s and post WWII, Scott Aviation began developing an SCBA designed specifically for firefighting use. The first SCBA designed by Scott was called the AirPac and introduced in 1945. This was the first version of the modern SCBA as we know it today. As the space race continued throughout the 1900s, SCBA technology would continue to improve allowing the SCBAs to become less cumbersome and for firefighters to carry less weight and more air. [5]

Types

Closed-circuit

Siebe Gorman Savox in a coal mining museum Aa savox1.jpg
Siebe Gorman Savox in a coal mining museum

The closed-circuit type, also known as a rebreather, [9] operates by filtering, supplementing, and recirculating exhaled gas. 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 the Siebe Gorman Proto, Siebe Gorman Savox, or Siebe Gorman Salvus.[ citation needed ] An example of modern rebreather SCBAs would be the SEFA.

As of 1987, under 30 CFR 11

Duration of closed-circuit SCBAs is somewhere between 1-4 hours. A closed-circuit SCBA system is negative-pressure, increasing the risk of leaks. [9]

There are two types of closed-circuit SCBA according to NIOSH:

  • Uses compressed oxygen.
  • Uses an oxygen-generating solid. This involves a chemical reaction between potassium superoxide with exhaled water and carbon dioxide. A chlorate candle has to be struck to start the device.

To reduce pressure buildup from use, a pressure-relief valve with saliva trap is included. Closed-circuit SCBAs are also noticeably smaller than open-circuit ones. [9]

Self-contained self-rescue devices are also closed-circuit SCBAs, working on the same principles, being designed for emergency use in mines, and lasting about one hour. [9]

Open-circuit

As of 1987, under 30 CFR 11

SCBA packs carried on a rack in a firetruck SCBA TruckMount JDiPierro.jpg
SCBA packs carried on a rack in a firetruck
30 CFR 11 approval label for an open-circuit, pressure-demand SCBA respirator 30 CFR 11 SCBA label.svg
30 CFR 11 approval label for an open-circuit, pressure-demand SCBA respirator

An open-circuit SCBA does not recirculate air; it instead allows respired air to be exhausted outside. While 30 CFR 11 does not restrict the gas that can be used (although compressed air is usually chosen), use of compressed oxygen is not allowed due to the system's exposure to outside air. Duration is usually limited to 30-60 minutes. [10]

There are two types of open-circuit SCBA according to NIOSH:

  • Demand: 2000 psi to the regulator from the main valve, plus a bypass valve in case of failure, with a two-stage regulator reducing pressure to 50-100 psi.
  • Pressure-Demand: Similar to demand, but with a spring in the diaphragm, which holds the admission valve open, for continuous air flow to the facepiece.

NIOSH emphasizes that facepieces between both SCBA types cannot be interchanged, but certain SCBAs can be switched to both 'demand' and 'pressure-demand' operation. However, both modes require different training. [10]

Common traits

SCBA pack with PASS device (ADSU) PASS device.png
SCBA pack with PASS device (ADSU)

Open-circuit industrial breathing sets are filled with filtered, compressed air. Typical open-circuit systems have two stage regulators. The first stage reduces the pressure from storage pressure of up to more than 300 bar to about 10 bar for supply to the second stage on the mask, which further reduces it to just above atmospheric pressure via a demand valve when the pressure drops on inhalation. A positive pressure mask has the demand valve set to close when the pressure inside the mask is slightly above the external ambient pressure, so when the mask is removed from the face or leaks around the skirt, the demand valve will free-flow.[ citation needed ]

An open-circuit rescue or firefighting SCBA has a full-face mask, also called the face-piece, a demand regulator, air cylinder, pressure gauge, (sometimes with an integrated PASS device), and a harness with adjustable shoulder straps and waist belt which lets it be worn on the back. The air cylinder is commonly 4 liter, 6 liter, or 6.8 liter, but other sizes are also available. The endurance of the cylinder can be calculated from the volume, pressure and breathing rate of the user. The formula: volume (in liters) × pressure (in bars) / 40 (litres per minute) - 10 minutes (the 10 minutes is a safety margin, or reserve), so a 6-liter cylinder, of 300 bar, is 6 × 300 / 40 - 10 = 35 minutes working duration. The fitness and level of exertion of the wearer affect breathing rate, and result in variations of the actual usable time of the SCBA.[ citation needed ]

Air cylinders are made of aluminium, steel, or of a composite construction (usually glass or carbon-fiber wrapped.) The composite cylinders are the lightest in weight and are therefore preferred by fire departments (UK: fire and rescue services previously called 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 5 years.[ clarification needed ] During extended operations, empty air cylinders can be quickly replaced with fresh ones and then refilled from larger tanks in a cascade storage system or from an air compressor brought to the scene.[ citation needed ]

Continuous-flow

Escape SCBAs, also known as ESCBAs, come with hoods, are meant for escapes only, and are operated in continuous flow mode. [11] [4] [12]

Escape only SCBAs, designed for escape from IDLH situations, regardless of type, are usually limited to 3-10 minutes. [10] [ clarification needed ]

Differences under 42 CFR 84

42 CFR 84 replaces the 30 CFR 11 respirator regulation used by NIOSH. As of 2001, quality assurance of SCBA harnesses is required. Labels have been updated to remove MSHA emblems from respirator labels, as MSHA is no longer involved in respirator approval except for respirators approved for mining. [13] [14] As a result, new SCBAs now have to specify whether the SCBA is "intended for mine use". [15]

Facepiece

SCBAs usually come with full-facepieces, [11] but can also come with half-mask or mouthpiece in demand or pressure-demand mode, though use of mouthpieces are limited to escapes only, as of 1987. [4]

Hoods and helmets are limited to continuous flow mode only, and are also used in air-line respirators in addition to escape-only SCBAs. [4] [12]

Usage

Elastomeric masks linked to backpack air tanks: self-contained breathing apparatus, worn by firefighters advancing with a firehose. Interschutz 2010 Brandbekampfung (1).jpg
Elastomeric masks linked to backpack air tanks: self-contained breathing apparatus, worn by firefighters advancing with a firehose.

There are two major application areas for SCBA: firefighting, and industrial use in confined spaces. [16]

For SCBAs used in firefighting, manufacturers typically prioritize fire resistance and weight reduction over cost. SCBAs used by the fire service also incorporate other features such as a PASS (personal alert safety system), which is a device that emits a loud alarm should the firefighter manually activate it or remain motionless for a certain amount of time. [17] [ non-primary source needed ] Other features may include Bluetooth connection to voice amplifiers or portable radios, digital heads-up displays, built-in infrared cameras, ePAR (electronic personal accountability report) system, point of view video recording, [18] and digital screens allowing the firefighter to more easily check their air supply. [19] [ non-primary source needed ] Every SCBA used in the fire service also comes with a vibralert system which alerts the firefighter as they get low on air [18] and a UAC (universal air connection), which allows the firefighter to give or receive air to other SCBAs through a trans-fill line by equalizing the pressure in both SCBA cylinders. Some SCBAs also come with a buddy-breather setup which allows both firefighters to connect their SCBAs and breathe while connected to each other. [20]

SCBAs are also used in a variety of industrial settings including mining, petrochemical, chemical, and nuclear industries. In some of the most hazardous conditions, SCBAs can be worn in conjunction with gas tight suits, which also aids in decontamination procedures. In the industrial setting, especially in confined spaces, a user will often be supplied air through a pressurized airline and will only carry compressed air cylinders for emergency escape and decontamination. [21] [ circular reference ]

Other regulations and standards

Volunteer fire fighter exiting live burn structure wearing NIOSH-certified SCBA, NFPA compliant turn-out gear, and holding a pike pole Volunteer Fire Fighter.jpg
Volunteer fire fighter exiting live burn structure wearing NIOSH-certified SCBA, NFPA compliant turn-out gear, and holding a pike pole
Example NFPA 1981 regulatory label Nfpa 1981 label.png
Example NFPA 1981 regulatory label

In the United States and Canada, 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 2018. [23] These standards are revised every five years. 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.

Any SCBA supplied for use in Europe must comply with the requirements of the Personal Protective Equipment Directive (89/686/EEC). In practice this usually means that the SCBA must comply with the requirements of the European Standard EN 137:2006. This includes detailed requirements for the performance of the SCBA, the marking required, and the information to be provided to the user. Two classes of SCBA are recognised, Type 1 for industrial use and Type 2 for firefighting. Any SCBA conforming to this standard will have been verified to reliably operate and protect the user from -30 °C to +60 °C under a wide range of severe simulated operational conditions.

Human factors

SCBA is intended to be personal protective equipment, but its use is not without cost. The weight of the unit and work of breathing affect the work capacity and agility of the wearer, and the full-face mask, while protecting the face and eyes from heat, smoke, and toxic gases, also reduces peripheral vision and awareness of the surroundings. The weight and harness straps may limit tidal volume, ventilation rate, and oxygen consumption, and heart rate may increase in comparison with the same exercise levels without the equipment. Shoulder harness straps of heavy SCBA can reduce free motion of the thorax which affects breathing. [24]

See also

Related Research Articles

<span class="mw-page-title-main">Scuba set</span> Self-contained underwater breathing apparatus

A scuba set, originally just scuba, is any breathing apparatus that is entirely carried by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment that is required for providing breathing gas to the diver, general usage includes the harness or rigging by which it is carried and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge. In the looser sense, scuba set has been used to refer to all the diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface-supplied diving systems and is allowed by the relevant legislation and code of practice.

<span class="mw-page-title-main">Rebreather</span> Portable apparatus to recycle breathing gas

A rebreather is a breathing apparatus that absorbs the carbon dioxide of a user's exhaled breath to permit the rebreathing (recycling) of the substantially unused oxygen content, and unused inert content when present, of each breath. Oxygen is added to replenish the amount metabolised by the user. This differs from open-circuit breathing apparatus, where the exhaled gas is discharged directly into the environment. The purpose is to extend the breathing endurance of a limited gas supply, while also eliminating the bubbles otherwise produced by an open circuit system. The latter advantage over other systems is useful for covert military operations by frogmen, as well as for undisturbed observation of underwater wildlife. A rebreather is generally understood to be a portable apparatus carried by the user. The same technology on a vehicle or non-mobile installation is more likely to be referred to as a life-support system.

<span class="mw-page-title-main">Respirator</span> Device worn to protect the user from inhaling contaminants

A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including lead fumes, vapors, gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respirators: the air-purifying respirator, in which respirable air is obtained by filtering a contaminated atmosphere, and the air-supplied respirator, in which an alternate supply of breathable air is delivered. Within each category, different techniques are employed to reduce or eliminate noxious airborne contaminants.

<span class="mw-page-title-main">Breathing apparatus</span> Equipment allowing or assisting the user to breath in a hostile environment

A breathing apparatus or breathing set is equipment which allows a person to breathe in a hostile environment where breathing would otherwise be impossible, difficult, harmful, or hazardous, or assists a person to breathe. A respirator, medical ventilator, or resuscitator may also be considered to be breathing apparatus. Equipment that supplies or recycles breathing gas other than ambient air in a space used by several people is usually referred to as being part of a life-support system, and a life-support system for one person may include breathing apparatus, when the breathing gas is specifically supplied to the user rather than to the enclosure in which the user is the occupant.

A breathing mask is a mask that covers the mouth, nose, and optionally other parts of the face or head, designed to constrain and direct the wearer's breath to and/or from a particular breathing apparatus. It may mean, or be part of, one of these types:

<span class="mw-page-title-main">Oxygen mask</span> Interface between the oxygen delivery system and the human user

An oxygen mask is a mask that provides a method to transfer breathing oxygen gas from a storage tank to the lungs. Oxygen masks may cover only the nose and mouth or the entire face. They may be made of plastic, silicone, or rubber. In certain circumstances, oxygen may be delivered via a nasal cannula instead of a mask.

<span class="mw-page-title-main">Immediately dangerous to life or health</span> Exposure to dangerous levels of airborne contaminants

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 adverse health effects or prevent escape from such an environment." Examples include smoke or other poisonous gases at sufficiently high concentrations. It is calculated using the LD50 or LC50. The Occupational Safety and Health Administration (OSHA) regulation defines the term as "an atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere."

This is a glossary of firefighting equipment.

<span class="mw-page-title-main">Hazmat suit</span> Protective suit against chemical, bacteriological, and nuclear risks

A hazmat suit is a piece of personal protective equipment that consists of an impermeable whole-body garment worn as protection against hazardous materials.

<span class="mw-page-title-main">Self-contained self-rescue device</span>

A self-contained self-rescue device, SCSR, self-contained self-rescuer, or air pack is a type of closed-circuit SCBA with a portable oxygen source for providing breathable air when the surrounding atmosphere lacks oxygen or is contaminated with toxic gases, e.g. carbon monoxide.

<span class="mw-page-title-main">Escape breathing apparatus</span> Self contained breathing apparatus providing gas to escape from a hazardous environment

Escape breathing apparatus, also called escape respirators, escape sets, self-rescuer masks, emergency life saving apparatus (ELSA), emergency escape breathing devices (EEBD), and Respiratory Protective Smoke Escape Devices (RPED), are portable breathing apparatus that provide the wearer with respiratory protection for a limited period, intended for escape from or through an environment where there is no breathable ambient atmosphere. This includes escape through water and in areas containing harmful gases or fumes or other atmospheres immediately dangerous to life or health (IDLH).

<span class="mw-page-title-main">Bunker gear</span> Personal protective equipment used by firefighters

Bunker gear is the personal protective equipment (PPE) used by firefighters. The term is derived from the fact that the trousers and boots are traditionally kept by the firefighters bunk at the fire station to be readily available for use.

<span class="mw-page-title-main">Breathing performance of regulators</span> Capacity of breathing regulators to function as specified

The breathing performance of regulators is a measure of the ability of a breathing gas regulator to meet the demands placed on it at varying ambient pressures and temperatures, and under varying breathing loads, for the range of breathing gases it may be expected to deliver. Performance is an important factor in design and selection of breathing regulators for any application, but particularly for underwater diving, as the range of ambient operating pressures and temperatures, and variety of breathing gases is broader in this application. A diving regulator is a device that reduces the high pressure in a diving cylinder or surface supply hose to the same pressure as the diver's surroundings. It is desirable that breathing from a regulator requires low effort even when supplying large amounts of breathing gas as this is commonly the limiting factor for underwater exertion, and can be critical during diving emergencies. It is also preferable that the gas is delivered smoothly without any sudden changes in resistance while inhaling or exhaling, and that the regulator does not lock up and either fail to supply gas or free-flow. Although these factors may be judged subjectively, it is convenient to have standards by which the many different types and manufactures of regulators may be objectively compared.

<span class="mw-page-title-main">Scott Air-Pak SCBA</span> Firefighting breathing apparatus

The Scott Air-Pak SCBA is an open-circuit, self-contained breathing apparatus designed to meet the National Fire Protection Association (NFPA) Standard 1981. All components, excluding the air cylinder, were designed and manufactured by Scott Safety. Formerly a division of Tyco International, Ltd., Scott Safety was sold to 3M in 2017.

<span class="mw-page-title-main">Orinasal mask</span> Breathing mask that covers the mouth and the nose only.

An orinasal mask, oro-nasal mask or oral-nasal mask is a breathing mask that covers the mouth and the nose only. It may be a complete independent item, as an oxygen mask, or on some anaesthetic apparatuses, or it may be fitted as a component inside a fullface mask on underwater breathing apparatus, a gas mask or an industrial respirator to reduce the amount of dead space. It may be designed for its lower edge to seal on the front of the lower jaw or to go under the chin.

A breathing tube is a hollow component that can serve as a conduit for breathing. Various types of breathing tubes are available for different specific applications. Many of them are generally known by more specific terms.

<span class="mw-page-title-main">Powered air-purifying respirator</span> Full-face respirator that provides filtered air to the wearer using an electric fan

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 pathogen, actively removes (filters) a sufficient proportion of these hazards, and then delivers the clean air to the user's face or mouth and nose. They have a higher assigned protection factor than filtering facepiece respirators such as N95 masks. PAPRs are sometimes called positive-pressure masks, blower units, or just blowers.

3M Scott Fire & Safety is an American manufacturer of respiratory and personal protective equipment including supplied air and air purifying respirators, compressors, gas detection systems and thermal imaging cameras. The company was founded in 1932 as Uniloy Accessories Corporation, and is located in Monroe, North Carolina. In 2001 it was acquired by Tyco International and in 2017 it was acquired by 3M.

<span class="mw-page-title-main">Supplied-air respirator</span> Breathing apparatuus remotely supplied by an air hose

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 (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. They may be equipped with a backup air tank in case the air-line gets cut.

<span class="mw-page-title-main">Glossary of breathing apparatus terminology</span> Definitions of technical terms used in connection with breathing apparatus

A breathing apparatus or breathing set is equipment which allows a person to breathe in a hostile environment where breathing would otherwise be impossible, difficult, harmful, or hazardous, or assists a person to breathe. A respirator, medical ventilator, or resuscitator may also be considered to be breathing apparatus. Equipment that supplies or recycles breathing gas other than ambient air in a space used by several people is usually referred to as being part of a life-support system, and a life-support system for one person may include breathing apparatus, when the breathing gas is specifically supplied to the user rather than to the enclosure in which the user is the occupant.

References

  1. ↑ Bollinger 1987 , p. 184
  2. ↑ IFSTA 2008, p. 190.
  3. ↑ IFSTA 2008, p. 191.
  4. 1 2 3 4 Bollinger 1987 , pp. 7–8
  5. 1 2 3 4 "SCBA_History". lishfd.org. Retrieved 2024-11-30.
  6. ↑ "www.divinghelmet.nl".
  7. ↑ "1916_MSA Gibbs". www.therebreathersite.nl. Retrieved 2024-11-30.
  8. ↑ "A brief history of our breathing apparatus". www.london-fire.gov.uk. Retrieved 2024-11-30.
  9. 1 2 3 4 Bollinger 1987 , pp. 55–56
  10. 1 2 3 Bollinger 1987 , pp. 59–64
  11. 1 2 Bollinger 1987 , p. 207
  12. 1 2 Bollinger 1987 , p. 65
  13. ↑ "DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service 42 CFR Part 84" (PDF). US Federal Register. pp. 26850-26893. Retrieved 2024-05-08.
  14. ↑ "CHANGES IN OCCUPATIONAL SAFETY REGS WILL PERMIT BETTER RESPIRATORS TO PROTECT AGAINST DUST AND DISEASE". NIOSH. 1995-06-02. Archived from the original on 1996-12-31.
  15. ↑ "STANDARD APPLICATION PROCEDURES FOR THE CERTIFICATION OF RESPIRATORS" (PDF). NIOSH. January 2001. Archived from the original (PDF) on 2003-03-19.
  16. ↑ Bollinger 1987 , p. 120
  17. ↑ US20150273248A1,Kuutti, Tommi Lennart; Barnitz, Jeffrey Acton& Emery, Clayton Josephet al.,"Self contained breathing apparatus (SCBA) electronics system",issued 2015-10-01
  18. 1 2 "Self Contained Breathing Apparatuses SCBA - Emergency Equipment - EEP". Emergency Equipment -- EEP. Retrieved 2024-11-12.
  19. ↑ "MSA G1 SCBA User Assets | MSA Safety | United States". us.msasafety.com. Retrieved 2024-11-12.
  20. ↑ "S.C.B.A. Considerations - Part 5: Universal Air Couplings and EBSS". Firehouse. 2006-08-21. Retrieved 2024-11-12.
  21. ↑ "Self-contained_breathing_apparatus". www.bionity.com. Retrieved 2024-11-12.
  22. ↑ "Chemical, Biological, Radiological, and Nuclear (CBRN) Respiratory Protection Handbook" (PDF). NIOSH. July 2018.
  23. ↑ "NFPA". NFPA. Archived from the original on 6 April 2018. Retrieved 5 May 2018.
  24. ↑ Louhevaara, V.; Smolander, J.; Tuomi, T.; Korhonen, O.; Jaakkola, J. (1985). "Effects of an SCBA on breathing pattern, gas exchange, and heart rate during exercise". J Occup Med. 27 (3): 213–216. PMID   3981278.

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