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This article intends to provide a general overview of self-contained breathing apparatus, the reasons for using it as an essential component of health and safety, the benefits of using it as PPE, use, testing and maintenance requirements.
The self-contained breathing apparatus (SCBA) is a piece of equipment used by firefighters, industrial workers, and others who need to breathe in hazardous environments. This is not to be confused with breathing apparatus used by divers, which is known as self-contained underwater breathing apparatus (SCUBA).
Introduction
Many occupations require people to enter atmospheres that are hazardous, have the potential to become hazardous or are immediately dangerous to life and health (IDLH). Although environments may not be immediately dangerous, depending on the nature of the site, there may be a chance that the environment could suddenly become hazardous before a worker can escape to safe air. This may be due to oxygen deficiency in a confined space or contamination from a gas or vapour release.
Breathing apparatus is generally associated with fire and rescue where firefighters don (wear) SCBA as one of their control measures prior to entering a hazardous atmosphere. SCBA is also widely used in the oil and gas industry where there are often high levels of hydrogen sulphide (H2S), which is the rotten egg smelling gas causing unconsciousness and death at relatively low levels. If there is a loss of containment such as a leak from pipework in a pressurised line, the atmosphere can almost immediately become unbreathable, and a worker will have seconds to don a BA set.
“if there is a loss of containment, the atmosphere can almost immediately become unbreathable”
The types of BA sets usually carried by oil and gas workers are smaller sets of limited duration, usually ten or fifteen minutes, which will provide enough air to allow the worker to walk cross and upwind to safe air. These emergency escape breathing apparatus sets (EEBA) must only be used for escape and never to be worn to enter a dangerous environment to carry out work or rescues of any kind.
SCBA sets are also commonly used by the mining industry, and it is due to this industry that the modern day SCBA have been developed and improved on.
Brief history
The history of the SCBA dates back to the late 19th century, when the first attempts were made to create a device that would allow individuals to breathe independently in dangerous environments. Figure 1 shows a smoke hood that was developed by Siebe Gorman. This used two pipes that supplied fresh air into the helmet. The air was provided by bellows outside using personnel to operate them. This did not prove really popular or suitable as the helmet was heavy, provided poor vision and the distance travelled was limited
by the airlines and the firefighting hose taken into the building.
One of the earliest known examples of a self-contained breathing apparatus was created in 1860 by the Frenchman Benoit Rouquayrol used for mines rescue, this was modified in 1865 by a naval officer, Auguste Denayrouze. Their device, known as the Rouquayrol-Denayrouze apparatus, consisted of a metal cylinder of compressed air that was worn on the back and connected to a mask that covered the nose and mouth. This was used mainly for diving. In the early 20th century, the SCBA began to be used more widely in industrial and military settings. During World War I, for example, the British Army developed the Smoke Helmet, which was a type of SCBA that allowed soldiers to breathe in smoke-filled trenches. In the United States, the Scott Aviation Company developed the first mass-produced SCBA in the 1920s, which was used primarily by firefighters. Scott SCBA sets are widely used today in firefighting, military, industrial and mining industries.
A further development of breathing apparatus was the Siebe Gorman Proto set. This was developed from around 1910 and was an industrial BA set commonly used in the mining industry. Fire brigades started to use these sets and from around the 1950s, they were routinely carried on fire appliances (fire trucks). This Proto set consisted of an oxygen cylinder and a bag containing a chemical, which removed the carbon dioxide from the exhaled air. Oxygen was then added to the air and re-breathed, hence these types of BA sets were known as re-breather sets. A nose clip and goggles were worn as separate pieces from the mouthpiece that allowed the wearer to draw air through the mouth and prevent the eyes being irritated from the smoke.
Throughout the 20th century, the technology behind the SCBA continued to evolve. In the 1950s, for example, the demand for lighter and more portable SCBAs led to the development of the demand regulator, which allowed users to breathe normally while wearing the device.
Another major development in the history of the SCBA was the introduction of the open-circuit system. Prior to this, most SCBAs used a closed-circuit system, which meant that exhaled air was recycled and breathed in again, as discussed with the Proto sets. The open-circuit system, on the other hand, allowed exhaled air to be released and replaced with fresh air from the cylinder. This improved the effectiveness and safety of SCBAs, particularly in environments with high levels of carbon dioxide. The introduction of lightweight carbon fibre cylinders further improved the mobility and effectiveness of SCBAs.
In recent years, advances in technology have led to the development of more advanced SCBAs, such as those with integrated thermal imaging cameras and communication systems. These devices allow firefighters and other emergency responders to navigate dangerous environments more effectively and communicate with each other more easily.
The hazards of dangerous exposure
Health and safety has evolved incredibly over the last fifty years with the introduction of the Health and Safety at Work etc. Act 1974, which is the primary piece of UK legislation relating to health and safety. Another equally important piece of legislation is the Occupational Safety and Health Act of 1970 (OSHA) which is the main legislative tool for the provision of protection to workers in the USA.
Both of these acts require employers to provide protection to workers, however, many of the hazards that we are aware of now were not seen as hazardous many years ago. Of particular documented concern now is the long term harmful effects of occupational exposure to hazardous materials or atmospheres.
In 2022, the World Health Organization‘s (WHO) International Agency for Research on Cancer officially declared firefighting as a Group 1 designation meaning it is accepted that firefighting is carcinogenic to humans. Up until this time, it was accepted that firefighters could develop cancer. The amount of toxins in smoke from burning products have varying effects on firefighters over time. More research carried out on firefighters around the world has shown that this group of workers suffer incredibly higher mortality rates than any other occupation.
Many of the causes of death are through heart diseases shown to be brought on by heat stress and the stresses of the heavy workload. Firefighters suffer from cancers such as blood related cancers, lung cancers, prostate cancers and other forms of tumours greater than any other occupation. It is likely that every firefighter will be able to talk about colleagues they have worked with who have been treated for cancer or who have passed away prematurely due to cancer or heart disease.
“the protection provided by SCBA is crucial in reducing the toxins being introduced to the body by inhalation”
According to the WHO, “sufficient evidence exists that they are at increased risk for bladder cancer and mesothelioma, which impacts tissue lining the lungs and other organs. Additionally, ‘limited evidence’ links firefighters to elevated risk of colon, prostate and testicular cancers, along with skin cancer and non-Hodgkin lymphoma.”
Not only are cancers prevalent in firefighters, they are showing in many of the families of firefighters, particularly partners who are in close contact with firefighters or their contaminated work clothing. Although firefighting PPE is generally washed at the fire station, many firefighters are forced to take their PPE home with them to wash, or to transport in their vehicles due to being sent to work at a different station to cover staff shortages or many of them are officers on call who respond from home to a fire scene. Even if PPE is washed at the fire station, most firefighters will bring their soiled shirts, t-shirts and trousers home to be washed and these are often heavily contaminated with carbonaceous contaminants.
It is now clear that the protection provided by SCBA is crucial in reducing the toxins being introduced to the body by inhalation, but this does not go far enough when considering occupational exposures. Even though the atmosphere itself may be no longer classed as IDLH, there will be many contaminants still in the atmosphere and on the clothing and bodies of the workers. Many of these contaminants will be absorbed through the skin or ingested when eating, smoking or drinking.
Workplaces should be encouraged to carry out a full analysis of how workers can be exposed to toxins or any other harmful environments and think on a much wider scale than just the exposure during an incident or when carrying out a routine activity that requires the uses of SCBA. Decontamination of workers should consider all exposure paths that could be encountered and put measures in place to eliminate or reduce them. There are many simple, effective and cheap methods of decontamination that can be implemented.
Having a set of cleaning/decontamination procedures that are easily understood and implemented by workers will encourage workers to follow them. Explaining the hazards in a clear way will educate workers especially when describing the potential effects on family members who may be exposed to contaminants carried home by the worker. Providing washing machines and drying facilities in the workplace for soiled or contaminated PPE and underclothing should be encouraged. Washing stations should be provided at strategic locations. There are specialist wipes now available on the market, which are proven to reduce many of the harmful contaminants that washing alone will not remove. These should be made available at regular locations to remove contaminants from the face, neck and hands as soon as the worker has left the hazardous environment. The provision of showers to encourage workers to shower after carrying out activities which may have contaminated them, or to shower before they travel home, should also be considered.
More structured protection measures should also be implemented, such as annual face fit tests for wearers of close fitting respiratory protective equipment (RPE), and regular health screening to monitor any changes in physiology will provide early diagnosis and treatment of workers. Workers who are required to wear RPE are required by law to undergo an annual face fit test, and it is the responsibility of management to ensure a face fit programme is implemented to ensure that competent people carry out the testing and that testing equipment is properly calibrated.
Even though a worker may have passed a face fit test on consecutive years using the same type of mask that is worn, over the years there may be facial changes, weight loss or gain, loss of teeth, or other facial changes, which may mean the worker would need to use a different size or type of RPE.
Components of a Self-Contained Breathing Apparatus
SCBA sets are made up of four main components.
Compressed air cylinder
A high-pressure cylinder, usually made of aluminium or composite materials, containing compressed breathing air of medical breathing grade. The cylinder is charged from a compressor. It is vital that the compressor is regularly serviced and the filters are changed following manufacturer’s recommendations, usually when a certain number of compressor hours have been reached. Air quality tests should also be carried out on a quarterly basis to ensure the air is safe to breathe. Air quality testing is carried out to determine the content of carbon monoxide, carbon dioxide, oil and water vapour in breathable air from compressors and compressed air cylinders. When mandatory by National Regulation, the presence of Nitrous gases must be determined as well. The air quality should conform to EN 12021 or NFPA 1989 dependent on which standard is adopted. It should be noted that these two standards have slightly different requirements for air quality test results and the standards should be carefully reviewed.
“workers who are required to wear RPE are required by law to undergo an annual face fit test”
Regulator
A device that reduces the high-pressure air from the cylinder to a breathable pressure, typically from 200-300bar cylinder pressure to 6-8 bar up to the face mask lung demand valve (LDV).
Mask
A full-face mask or half-mask that covers the face and provides a secure seal around the mouth and nose to prevent outside air from entering. The mask operates at a positive pressure inside so in the event the mask becomes dislodged or moves away from the face due to facial movements or sweating, air is forced out of the mask preventing the ingress of external air. Attached to the mask is the lung demand valve (LDV) which is another pressure reducer. There is usually a way of the wearer being able to get additional air by pressing a button on the LDV or turning a valve, the operation of this button will force more air into the mask which will provide cooling air and also enable the wearer to breathe as heavily as required. This is not often used by firefighters as operation of this device reduces the amount of air in the cylinder and reduces the available working duration of the cylinder.
Harness and backplate assembly
A set of straps and buckles that secure the cylinder onto the backplate and mask to the user’s body and provide a comfortable and adjustable fit. Most backplates are now a type of composite plastic material for strength and low weight. Older backplates were made of steel which were much heavier. Many of the modern backplates now have adjustable shoulder and waist points with pivoting moveable parts which can allow the wearer to move and bend in all directions and the backplate will move with them rather than remaining rigid and restricting the movement of the wearer.
Additional components
Most SCBA sets also include additional components, such as a personal radio, a pressure gauge to monitor the air supply, a low-pressure warning alarm, and an emergency breathing apparatus or secondary attachment for use in case of equipment failure or other emergency situations. Often this is used for airline for extended duration wearing or to supply additional air to a worker who may be trapped and is running low on air.
SCBA sets used for fire and rescue purposes also have a distress signalling device which can be operated manually or that operate automatically after 30 seconds of non-movement which may indicate a collapsed wearer. Rescue SCBA sets also usually have a torch and often a thermal imaging camera attached on an extendable lanyard. More frequently, cable cutting tools are added to allow a firefighter to cut themselves free from entanglement in cables which may have dropped down from or above a ceiling during a fire. There have been several instances of firefighters dying due to entanglement in melting electrical cables and plastic ducting during fire and rescue operations.
A number of fire and rescue services now use a technology called telemetry (radio communications), which allows a person outside the risk area (entry control officer) to monitor the breathing rate of the individual wearers, see their cylinder contents and see the time calculated before they have to leave the risk area. The time a BA cylinder lasts is dependent on the pressure of the cylinder, the size of the cylinder and the breathing rate of the wearer, which is further dependent on how hard they are working or how hot the environment is. The sets that use telemetry also indicate to the entry control officer if the distress signalling device has activated and allows the entry control officer to activate an evacuation signal directly to each individual wearers set or all of them at once.
Telemetry sites also have a recording capability (similar to an airplane black box) which can be removed and have the data downloaded. This data will allow an organisation to monitor that the SCBA sets are being tested in accordance with their requirements or in the event of an injury or death to the wearer, the organisation can review all the breathing history of the wearer to determine how the wearer was reacting to a situation or if there was a critical set failure.
Training and proper use of SCBA
It will be sufficiently clear from the information already presented that SCBA sets are critical elements of PPE and are complex enough that rigorous training programmes are required to ensure that workers are competent to use them.
Before a worker is trained on the use and operation of a SCBA set, the suitability of the worker to wear SCBA should be evaluated. This may be a combination of a full job analysis to determine the requirement for SCBA and determining the type of SCBA required (EEBA, 30 minutes, 45 minutes, extended duration, air-line etc.), then assessing the workers to ensure they are physically fit. Each occupation may have their own fitness standards therefore this article cannot be prescriptive. Fire Services generally have national standards of fitness and attributes required whereas other industries may have their own internal occupation/industrial health and hygiene specialists who will set a criteria.
Once the need has been established for SCBA and the workers required to be trained are identified, the training programme should be led by a person who is deemed competent to train and assess the use of SCBA. There are usually a number of elements related to the training of workers to use SCBA.
“SCBA sets are critical elements of PPE and are complex enough that rigorous training is required”
The first element is an understanding of human physiology and the importance of avoiding exposure to contaminants. They must learn to recognise the signs of physical or mental stress within themselves or their colleagues when using SCBA. An early recognition of a wearer in distress can ensure they are brought to safety or remove themselves before they become completely incapacitated.
The second phase will be knowledge of how the SCBA set works, how to put a fully charged cylinder on, how to test the set, how to don (wear) the set and how to clean and maintain it after use so it is ready for its next use. The importance of maintenance and test records in a log book for each set is also vital.
The third phase of a training programme should focus on the safe wearing procedures and the procedures to be followed when the set is being worn in an irrespirable atmosphere. The full understanding and adherence to safe working procedures are the corner stone of any compliant health and safety management system. The safe use during training sessions should be evaluated through a number of training scenarios in realistic conditions once full training has been provided. Anyone who has not been deemed safe or competent should undergo further training and assessment before being authorised to wear SCBA in hazardous environments.
Firefighting or fire and rescue is a completely specialised field of work requiring SCBA and the training for a firefighter to wear SCBA in a number of different situations will usually be a two-week intensive programme. The training for an industrial worker may only be one or two days as their requirements for wearing SCBA will be totally different. Therefore, the training programme must be suitable for the work and workers to ensure that at the end of the training course, they can be tested and prove that they are competent.
Continuous training and assessment should also be implemented by management to ensure that workers are still following safe working practices and have not developed bad habits over time which may mean they are not testing or using SCBA sets correctly.
Maintenance, inspection, and care of SCBA
A maintenance programme should be implemented for all SCBA sets. Regular testing, use and cleaning of the SCBA sets should be scheduled according to the needs of the organisation and always in accordance with the manufacturer’s recommendations. Maintenance of SCBA sets is only to be carried out by a trained, usually manufacturer-certified technician. Under no circumstances should any worker who is not certified as a SCBA set technician, attempt any modifications or repairs to the SCBA set. This could at the very least invalidate any warranty, or at worst, cause a catastrophic failure of the set during use leading to serious injury or death.
Trained SCBA wearers should only be allowed to test the SCBA set and ancillary equipment as part of the routing testing required, change the cylinder, clean the SCBA set following the manufacturer’s recommendations, and wear the set. No other tampering should be accepted. Even when washing or cleaning the BA set, there are certain precautions required to prevent water entering particular parts such as the cylinder to set connector, connecting couplings, low and medium pressure supply hoses, etc. If water enters a part of the BA set that is not allowed by the manufacturers, again catastrophic failure of the set during use will be the likely outcome.
Manufacturers of SCBA sets will produce guidance documents which will mandate that certain components of the SCBA sets should be replaced periodically or undergo certain functional tests, and this will usually mean the SCBA set being sent to a certified workshop. SCBA cylinders are required to be hydrostatically tested on a periodic basis usually five, seven or ten years. Most types of cylinders have an end of service date stamped on the cylinder body which means that the cylinder should be replaced, removed from service and destroyed. Sufficient reserve SCBA sets should always be available to allow for the sets which have been sent away for service or repair.
Conclusion
This article attempts to introduce readers to the importance of SCBA sets and respiratory protection to ensure that this most vital component of worker PPE is selected, tested and used in a safe and competent manner. Many occupational health hazards are not known until they show themselves in workers, sometimes many years later and by then the damage is already done. Occupational cancers are rising due to the huge expansion of the use of chemicals and the modifications of hydrocarbons in particular.
Our homes are filled with many more chemicals than at any other time and many of these chemicals are not broken down at all. Once they are in the environment or in our bodies, they stay there. Occupational screening and robust industrial hygiene procedures are required to protect workers. Education is key to the understanding of the hazards in workplaces in certain types of industry. Many firefighters will recall not being required to wear SCBA for fire occurring outside and this will be the same for many industrial workers who will recall entering confined spaces or contaminated atmospheres before the risks were widely understood. It takes a few minutes to put PPE on properly and wear SCBA, yet the effects of not doing so will remain for many years, and the worker may suffer industrial diseases even after they have retired. There is no longer any excuse for not doing the right thing. Protect yourselves, your families and protect your work force.
