# Oxygen Regulator Flash Severely Burns One Fire Fighter - Florida/Recommendations/Discussion

​ RECOMMENDATIONS/DISCUSSION
Recommendation #1: Fire departments should use oxygen regulators constructed of materials having an oxygen compatibility equivalent to brass.
DISCUSSION: Aluminum alloys are attractive candidate materials for pressure vessels because of their high strength-to-weight ratios. High pressure oxygen system components for portable or flight use must be lightweight, so it may appear to be desirable to build their housings from such lightweight metals as aluminum. The use of aluminum alloys in lines, valves, and other components should be avoided whenever possible because they easily ignite in high-pressure oxygen, burn rapidly, and have very high heats of combustion. Aluminum is ignited exceptionally easily by friction because the wear destroys its protective oxide layer; it should not be used in systems where frictional heating is possible.
Aluminum is easily ignited by particle impact, and aluminum particulate is a far more effective ignition source than many other metal particulate tested to date (titanium particulate has not been tested). High-pressure oxygen systems fabricated from aluminum must be designed with extreme care to eliminate particulate. Testing has ​shown that aluminum is substantially more flammable in oxygen than brass or other high copper or high nickel alloys.
Sources indicate that commonly used aluminum alloys can easily burn in the presence of high-pressure pure oxygen once an ignition is present. Thus, aluminum will burn in pure oxygen at a pressure of 35 pounds per square inch (psi) (this is about twice the normal atmospheric pressure) whereas some brass alloys require over 5000 psi of pure oxygen to burn. Aluminum will also produce approximately 10 times the amount of heat provided by copper alloys when burning.
One concern of using aluminum in the regulator flow path is the possibility of particle impact and the aluminum not being able to contain the ignition. Particles can be introduced into oxygen resuscitators in many different ways. Experts suggest the presence of a particle or particles in the cylinders is not as problematic as the design of the oxygen flow path and the materials used.
The cylinder has a post valve that closes off the oxygen opening and allows the regulator to attach (Diagram 2). When the post valve is screwed into the aluminum cylinder, there is a possibility that the two metals rubbing together (galling) could create metal particles that would remain enclosed in the cylinder body. Galling is a condition involving smearing and transfer of material from one surface to the other and particles could be introduced by metal-to-metal of seals rubbing which occurs when the post valve is opened and closed. The frictional heat of the galling could lead to ignition of the valve; or the particles generated by the galling could cause malfunction or ignition of another component within the regulator. Therefore, the design of the regulator's flow path should be resistant to ignition if particles should occur. Experts suggest the regulator flow path should be lined with brass, bronze, or a similar material which would resist particle ignition, and that using such a material would shield the particle ignition and provide the opportunity to burn out. Particulate migration from the cylinder can be minimized by the installation of a standoff tube (bayonette) at the inlet of the post valve.
Experts suggest that the design of the regulator involved in this incident allowed for combustion in the high-pressure port to punch through the main seat directly and progress into the piston barrel, leading to rapid involvement of the low-pressure components and venting of combustion byproducts outward (through the vent ports).
In this incident, the regulator (with the aluminum flow path) could not contain the ignition of the particle impact. The significant amount of aluminum in this regulator, directly exposed to the high-pressure environment and oxygen flow, produced a design that was susceptible to an ignition mechanism of this nature. The testing laboratory recommended that the flow path should be constructed of a metal such as brass or bronze to reduce the risk of a flash.
For further information concerning a regulator in use, NIOSH recommends that fire department’s contact the manufacturer of the specific regulator to determine if the regulator contains any aluminum components exposed to oxygen in the high pressure end of the regulator.
Recommendation #2: Fire departments should ensure that the cylinder is placed in an upright position, the cylinder post valve is pointed in a safe direction (away from the operator), and opened then closed before the regulator is attached to the cylinder.
DISCUSSION: After removing the valve protection cap, the cylinder post valve should be opened slowly for an instant to clear the opening of particles of dust or dirt, being careful to point the valve opening away from personnel and in a safe direction. This will help prevent particles from being introduced into the regulator.
Cylinders are generally stored on the fire trucks in a horizontal position, which could allow particles to rest near the neck of the cylinder. Whenever possible, cylinders should be placed and secured in an upright position not only when in storage, but also when in use. If cylinders are stored in an upright manner, any particulate in the cylinder would generally settle in the bottom of the cylinder and not as easily entrain in the oxygen flow discharge.
In this incident, the cylinder was lying in a horizontal position when the victim opened the airway bag. When he placed the cylinder in a vertical position and opened the post valve, the regulator flashed. It is possible that particles inside the cylinder were present near the neck of the cylinder, and when the valve was opened the particles were forced into the oxygen flow path. ​Recommendation #3: Fire departments should ensure that when opening a cylinder post valve with the regulator attached, it should be opened slowly and positioned away from the operator and other people.
DISCUSSION: The Compressed Gas Association Manual, CGA G-4, Section 4.4.10, recommends the following: Never to permit oxygen to enter the regulator suddenly. Always open the cylinder valve slowly. Stand to one side and not in front of or behind the regulator when opening the cylinder valve. Never use wrenches or tools except those provided or approved by the oxygen regulator manufacturer. Avoid the use of a wrench on valves equipped with handwheels. Never hammer a valve handwheel in attempting to open or to close the valve. If a valve cannot be opened by hand, notify the supplier.
The fast opening of the valve could subject passageways or components to adiabatic compression (rapid compression with an associated rise in gas temperature, potentially to a material’s ignition point), which could result in hot spots and possible ignition of nonmetallic or particulate contaminates. Fast opening of the valve also provides the possibility of particles being forced into the flow path of the regulator. Once the particles are introduced into the flow path, it is also possible that the particles can collide with the filter located underneath the inlet screw or an additional target (Diagram 1). The filter will then act as the target which could result in the ignition of the metal particle.
The regulator should be positioned away from the operator (and other people) when the cylinder valve is opened and to let the regulator pressurize before looking at the gauge. If possible, the cylinder should be positioned upright and placed between the operator and the regulator (regulator barrel pointed away from the operator). This way an operator can open the cylinder valve from arms length away. Operators typically look at the gauge when the cylinder valve is opened. It is recommended that operators not try to read the gauge until the regulator has fully pressurized.
In this incident it is unclear if the victim opened the valve slowly. Test results concluded that the particle ignited in the area of the bronze sintered-inlet filter. Once ignition took place, the aluminum surrounding the filter ignited and released outward, causing injury to the victim. Laboratory tests have concluded that aluminum alloys will readily sustain combustion at pressures as low as 35 pounds per square inch ambient (psia) and produce approximately 10 times the heat of copper alloys when burning.
Recommendation #4: Fire departments should ensure that fire fighters are trained and aware of safe handling procedures pertaining to oxygen systems.
DISCUSSION: Fire departments should provide fire fighters with training in safe handling of oxygen resuscitators including operating procedures, maintenance, cleaning, visual inspections, and hazards that can occur. The operation of oxygen resuscitators is not a complicated task; therefore, training is sometimes overlooked. The operators should not only be able to operate oxygen resuscitators, but also know how to care for them and be aware of hazards involved with their use. Fire fighters are sometimes put in complicated situations where they have to administer oxygen to patients in the vicinity of grease, oil, gas, or other dangerous substances. Fire fighters should be trained to know what to do in these complicated situations and understand the proper maintenance procedures as well as when to report that a system needs repair.
Additionally, operators should be instructed to first open the cylinder valve slowly, letting the regulator pressurize, and then fully open the cylinder valve. What often happens is that the operator opens the valve just slightly, then sees the gauge register pressure, and then doesn’t fully open the cylinder valve. Fully opening the cylinder valve has two positive effects: 1) When the valve is not fully opened it can cause deformation of the cylinder seat valve and this has been suspected to be an ignition source; 2) Opening the cylinder valve against the stem gasket (i.e., fully opening and back seating the valve) helps keep oxygen from leaking past the stem gasket during use.
Operators should also use care when installing the inlet gasket. Installation of this gasket is a good way of contaminating the regulator/cylinder valve if the operator’s hands or components are not clean. Care should also be used to tighten the regulator onto the cylinder valve to prevent leakage of oxygen past the seal during use.
To further assist in the understanding of these areas, fire departments can refer to, and follow, the Compressed Gas Association’s CGA G-48 manual and additionally ASTM’s documents regarding training.
DISCUSSION: Fire departments should ensure that oxygen cylinders are stored in a specific controlled location. Oxygen cylinders should be kept free of flammable material, especially oil, grease, or any other readily combustible substance. Oxygen cylinders should also not be placed where oil can drip on the cylinder, its valve, or other attachments. It is possible that these substances could be introduced into the cylinder if they are present. If a cylinder comes in contact with a flammable substance or has been around a flammable substance where a possible contaminant could be introduced into the cylinder, the cylinder should be removed from service and the supplier contacted.
Cylinders should remain in a cool area while not in use. Cylinders should not be stored above 125°F (51.7°C) or used above 120°F (48.9°C). Cylinders should never be allowed to reach temperatures exceeding 125°F (51.7°C), because of the rise in pressure inside the cylinder with increasing temperature. Therefore, cylinders should never be placed near furnaces, radiators, or any other source of heat.
Cylinders should also be stored with a plastic cap over the post valve opening to reduce the possibility of contaminate build-up around the valve opening. The plastic caps should be placed on the cylinders post valve as soon as they are re-filled. Whenever practical, the cylinders should also be stored in a secured vertical position.
Additionally, all unused ports on the regulator should be capped off when in storage or in use to reduce the possibility of contaminates entering the regulator.
Recommendation #6: Fire departments should ensure that oxygen refilling stations and maintenance areas where oxygen equipment is serviced, are in a locked air-conditioned room that is clean, and free of dirt, oils, and grease.
DISCUSSION: Some fire departments refill their own cylinders, while other fire departments contract out the process. Departments that refill their cylinders should have an area dedicated for the refilling system that can be locked when not in use. This will reduce the risk of tools used for the process being removed, contaminated, and reintroduced to this environment. This area should be kept clean and free of oils, grease or any other combustible substance. During the refilling process, the post valve opening is generally left uncovered until the tank is refilled, leaving the valve available to collect contaminants. Keeping the area separate, locked, and clean should reduce the possibility of contaminants entering the area.
The refilling process should be completed by an individual who has been properly trained. The individual should have clean hands free of any contaminants, and if using gloves, should use a clean pair that is used only for this process. All tools and materials used in this process should be routinely cleaned and used only for this process. The area of the refilling station should be air conditioned to maintain adequate temperatures.
Maintenance areas should be kept clean, especially when gauges are being replaced; after the gauge is removed, the gauge port should be inspected for signs of contamination and the gauge should be inspected for contamination (oil coming from gauge port) etc.
Recommendation #7: Fire departments should ensure that any components added to the regulator, such as gauge guards, are installed so that they do not block the regulator vent holes.
DISCUSSION: Gauge guards can be installed on regulators to protect the gauge from being damaged. However, if any additional components (such as a gauge guard) are installed on the regulator, they should be supplied by the manufacturer and installed so as not to block the regulator vent holes. Covering of the vent holes could restrict the vents from functioning properly. Although not a contributing factor in this incident, if a fire would occur on the interior of the regulator, it would not be able to vent properly which could result in a significantly larger amount of damage.
* ↑ Newton, BE. Report to State of Florida Fire Marshal’s Office concerning oxygen resuscitator fire. Wendell Hull & Associates, Inc., Las Cruces, NM, September 11, 1998. Canadian Standards Association [1987]. Pressure regulators, gauges, and flow- metering devices for medical gases. Ontario, Canada, CAN CSA-Z305.3-M87. ASTM. Standards related to flammability and sensitivity of materials in oxygen-enriched atmospheres [1997]. West Conshohocken, PA, ASTM PCN 03-704097-31. National Aeronautics and Space Administration [1983]. Design guide for high pressure oxygen systems, Washington, DC, Publication 1113. Newton, BE., Personal communication regarding the review of NIOSH FACE report 98-F23, January 13, 1999.
* ↑ National Aeronautics and Space Administration [1996]. Safety standard for oxygen and oxygen systems. Washington, DC, Publication NSS 1740.15.
* ↑ Newton, BE., Personal communication regarding the review of NIOSH FACE report 98-F23, January 13, 1999.
* ↑ Compressed Gas Association [1996]. 4.0 High pressure oxygen cylinders. Oxygen CGA G-4. 9th ed. Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202.
* ↑ National Aeronautics and Space Administration [1983]. Design guide for high pressure oxygen systems, Washington, DC, Publication 1113. National Fire Protection Association [1994]. NFPA 53: Guide on fire hazards in oxygen- enriched atmospheres. Quincy, MA.
* ↑ Compressed Gas Association [1996]. 4.0 High pressure oxygen cylinders. Oxygen CGA G-4. 9th ed. Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202.
* ↑ Werley BL, ed. [1991]. ASTM Committee G4.05 fire hazards in oxygen systems: ASTM standards technology training coursebook. 2nd ed. Philadelphia, PA. 11. Compressed Gas Association, Inc. CGA P-1, Safe handling of compressed gases in containers. Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202.
* ↑ Newton, BE., Personal communication regarding the review of NIOSH FACE report 98-F23, January 13,1999.
* ↑ ASTM. Standards related to flammability and sensitivity of materials in oxygen-enriched atmospheres [1997].
* ↑ Compressed Gas Association [1996]. 4.0 High pressure oxygen cylinders. Oxygen CGA G-4. 9th ed. Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202. National Fire Protection Association [1994]. NFPA 53: Guide on fire hazards in oxygen-enriched atmospheres. Quincy, MA.
* ↑ Werley BL, ed. [1991]. ASTM Committee G4.05 fire hazards in oxygen systems: ASTM standards technology training coursebook. 2nd ed. Philadelphia, PA. Compressed Gas Association, Inc. CGA P-1, Safe handling of compressed gases in containers. Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202. National Fire Protection Association [1990]. NFPA 50: Standard for bulk oxygen systems at consumer sites. National Fire Protection Association, Batterymarch Park, Quincy, MA. National Fire Protection Association [1993]. NFPA 99:Standard for health care facilities. National Fire Protection Association, Batterymarch Park, Quincy, MA.