50 years of SCBA: Innovations to breathing apparatus most significant development in fire service
Innovations to breathing apparatus most significant development in fire service
December 6, 2007
By Rob Evans
Firefighters are often referred to as smoke eaters, but over the past five decades the introduction of and improvements to self-contained breathing apparatus (SCBA) have ensured that the name has become just that, a name. Before this time, firefighters would use dampened cloths or canister masks for entry into the dangerous atmospheres encountered on their responses.
Developed in 1942 and used well into the '60s by fire departments was the popular Chemox, made by Mine Safety Appliances Company (MSA). The design of the Chemox was quite simple, with the CO2 exhaled by the firefighter mixing with K2O2 in the canister, producing oxygen that filled two reservoirs that looked like lungs. Firefighters would inhale fresh oxygen from these lungs and the process would repeat. The downfall to these apparatus was that the amount of oxygen produced was not measurable and an approximate time limit of three-quarters of an hour had to be monitored closely because no oxygen level gauge was available.
During this period, many companies continued to develop SCBA using compressed air and variations of the Cousteau-Gagnan regulator. This regulator was developed by the French and Germans during the Second World War in 1943 and was a demand-style regulator. When a breath of air was required the user would simply breathe in and the regulator would supply air from an attached tank. The final development of a two-hose concept with an inhalation hose, a mouthpiece and exhalation hose with a flapper-type exhaust valve occurred after early trials in January and February of 1943 and patents were taken out on this hose and exhaust system. For the first number of years it was a chore for Scott Aviation to convince the fire service that the 6000 B4A Air-Pac, first developed in 1945, had a place in the fire service. The SCBA had a demand-type regulator and continued to be used on Scott's Air-Paks while the company continued to work within the airline industry developing the yellow breathing masks on commercial airliners, fighter pilots' oxygen masks and an underwater system called the Hydro-Pak.
The Scott Air-Pak II introduced the pressure/demand style regulator. In 1967, MSA introduced its Model 401 Demand air mask. Many of the fire departments that used the Chemox made the switch to this SCBA as their first compressed air breathing apparatus. Shortly afterwards in 1971 the NFPA made its first attempt at regulating breathing apparatus in the fire service. NFPA 19B, Standard for Respiratory Protective Equipment for Firefighters, was introduced in the spring of that year with the intent of guiding fire departments away from chemical breathers to demand-style SCBA.
In 1976 Scott Health & Safety, formed in 1967 after a conglomerate of companies purchased Scott Aviation, developed the first high pressure (4,500 psi) SCBA in partnership with NASA. Also in 1976, MSA produced the first fully wound composite cylinders, also with technology developed by NASA. These bottles were welcomed by firefighters and their backs; they weighed as much as nine pounds lighter than what was used in the past.
Things have moved much more quickly in the past two decades with withdrawal of NFPA 17B and subsequent adoption of NFPA 1981, Standard on Self-Contained Breathing Apparatus for Firefighters.
In this first edition, open circuit breathing apparatus was required to use positive pressure. Positive pressure in the mask of the SCBA wearer prevented toxic gases from entering the mask and incapacitating the firefighter. This was about the time that Scott Health & Safety developed their Air-Pak Fifty 2.2, 3.0 and 4.5 (2,216, 3,000 and 4,500 psi). During 1981, MSA began to offer its users three different sizes of masks to wear. The small, medium (standard with their SCBA) and large masks gave firefighters the ability to fit-test their facepieces. This would not be required in NFPA 1500 until six years later.
In the mid-' 80s, synthetic threads such as Nomex started to make an appearance in the construction of SCBA. Nomex was more far more durable than nylon and other materials, with its main feature being that it was fire resistive and could hold up against cuts, abrasions and chemicals. MSA began using Nomex in strapping of SCBA in 1984. Visibility of firefighters was addressed by MSA in 1986 with the addition of reflective coatings on SCBA harnesses. The next year MSA became the first SCBA to comply with NFPA 1981-1987 edition with its Ultralite II and Custom 4500 II air masks. This second edition changed the name of the Technical Committee to Fire Service Protective Clothing and Equipment and established a subcommittee on breathing apparatus.
Changes to the standard in the third (1992) edition included new requirements for third-party certification and quality control, new heat and flame test for the entire SCBA, revisions of testing for facepiece lens abrasion and communications.
The fourth edition of the standard, in 1997, incorporated new requirements for surrogate cylinders to replace actual breathing gas cylinders during the vibration testing. Another new requirement of adding a redundant end-of-service indicator was included in the standard as well.
The introduction of the heads-up display (HUD) was a very innovative requirement added to the fifth edition released in 2002. The heads-up display gives the users of SCBA a visual indicator of the remaining breathing air in their cylinder. The other addition was that if the HUD was powered by a power source, then that source status would also be shown.
Due to input from the fire service another safety feature was added to the requirements. The addition of a universal air connection means that trapped firefighters can have their air tanks replenished by any other SCBA. NFPA makes it clear that this is not a buddy system. This is not permitted by NIOSH standards, which all SCBAs must meet to comply with NFPA 1981. Again, MSA was the first to have an air mask, the MMR Xtreme, which complied with this 2002 edition. This product was also the first to comply with the NIOSH CBRN standard.
The NIOSH CBRN standard is one of the biggest additions to the most recent sixth edition of NFPA 1981-2007, Standard on Open-Circuit Self-Contained Breathing Apparatus (SCBA) for Emergency Services. The name itself has been changed and the standard has been completely revised to include:
- New breathing air cylinder retention requirement in the mounted position;
- Mechanical voice diaphragm performance requirement increased to 80 per cent minimum score at 1.5 metres;
- New voice communications system with at least an 85 per cent score at three metres;
- New independent pressure gauge that would not be affected by failure of the heads-up display (HUD);
- New water-immersion requirements for electronic devices that are part of the SCBA that must function properly and remain watertight after six exposures to 177 C for 15 minutes and water submersion to 1.5 metres;
- New, low-power capacity requirements for electronic devices to assure that such devices will continue to function properly for at least two hours following activation of the low power source signal.
Who knows what the next edition of NPFA 1981 will bring but firefighters can be assured that it will take them further away from the "smoke eater" moniker than ever before.
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