Real world oxygen fire evidence underscores the need for safety

Since 1988, WHA International, Inc. has investigated oxygen fires, documenting hundreds of incidents and related fire-damaged artifacts.

These items range from small regulators to large industrial valves and piping. Some items are mostly intact, while others are largely consumed and barely recognizable. Regardless of where they came from, each represents a unique case study from a real-world oxygen fire incident. While many of these incidents came at the tragic cost of human lives, their subsequent investigations resulted in better understanding and improvements in industry.

Today, these investigations and their artifacts provide continual opportunities for our engineers and investigators to analyze and evaluate the intricacies of the fire patterns, much of which we discuss in our technical training courses. Many of them also inform industry reports and papers published through entities like ASTM International. They each provide an important reminder of the hazards of working with oxygen.

Below, we invite you to join us for a sobering look at some of the artifacts and case studies from WHA that underscore the need for oxygen safety.

Incident 1: Medical oxygen cylinder with aluminum regulator

In October of 1995, responders arrived at the site of a medical emergency call in Boone, North Carolina. They began ventilating a patient with gaseous oxygen from this high-pressure medical oxygen cylinder, and as they were preparing to transport the patient, a catastrophic burnout occurred within the aluminum regulator. Flames and molten slag from the regulator erupted from the carrying case and engulfed the upper torso of the EMT who was carrying it.

In the late 90s, WHA investigated a total of 28 oxygen fires related to this type of aluminum oxygen regulator, the majority of which involved fire departments or emergency services. Between 1993 and 1999, 11 health care workers were burned, two ambulances were destroyed, and a fire station was damaged.

Each incident involved regulators primarily constructed of aluminum, which can be susceptible to ignition and burning under certain conditions if it is not well-protected in these high-pressure medical applications.

In response to these incidents, the Center for Devices and Radiological Health, a division of the US FDA, began an extensive investigation, calling on the expertise of WHA International, NASA-WSTF, and ASTM International for answers.

Ultimately, WHA engineers helped develop a new international standard for “promoted ignition” testing of medical oxygen regulators and other oxygen components. They also recommended regulator design improvements, including more oxygen compatible materials where needed (such as brass, which is resistant to ignition and burning in oxygen up to very high pressures).

To read more about our investigation, read our case study MEDICAL OXYGEN REGULATOR RESEARCH AND TESTING PROTECT USERS AROUND THE WORLD.

Incident 2: Industrial Ball Valve fire

In July 2001, this 150 mm (6 in) ball valve was situated in an industrial oxygen pipeline when it experienced a catastrophic burnout, resulting in significant damage, personnel injury, and the tragic death of the valve operator.

WHA was contacted to provide forensic investigation and failure analysis of the incident, and the investigation identified four main contributing factors that lead to the fire:

  1. Incorrect materials (delivery order did not match the order specification)
  2. Contamination (valve was not properly cleaned for oxygen service)
  3. Lack of visual inspection prior to assembly (no materials verification or cleanliness verification)
  4. Incorrect operation (valve was opened under a pressure differential which created conditions within the valve to support ignition of the contaminants and materials of construction)

This incident demonstrates the potential for extreme fire consequences in oxygen pipeline systems if industry best practices are not implemented. Read more about our investigation in this CASE STUDY: LARGE INDUSTRIAL BALL VALVE FIRE.

Incident 3: LOX Gate Valve Oxygen fire

During startup of a large industrial liquid oxygen (LOX) system, this gate isolation valve experienced an internal ignition that propagated in the valve and breached the component under pressure. Tragically, the resulting fire led to the death of two operators.

WHA’s investigation of this fire demonstrates the importance of verifying the oxygen compatibility of a material in its final state, AFTER that material has been fully manufactured. In this instance, we found that a contaminant likely used in the manufacturing of the valve’s stem packing had made its way into the valve. There, through operation and exposure to the environment, the contaminant migrated into a severe location where it ignited and produced a kindling chain that led to catastrophic burnout.

At the tragic cost of two human lives, this incident resulted in a change in industry perspective regarding oxygen safety of LOX valves.

You can read more about the investigation of a similar LOX gate valve in our CASE STUDY: FAILURE ANALYSIS OF A LIQUID OXYGEN VALVE INTERNAL FIRE.

Incident 4: Welding Dam Industrial Oxygen Pipeline Fire

This 250 mm (10 in) stainless steel pipe was believed to be impervious to oxygen fires under its operating conditions at just 2 bar (30 psig) pressure. However, carelessness by contractors in the pipeline assembly process led to an incident. Fortunately, no one was hurt in the ensuing oxygen fire.

WHA’s investigation found a melt flow pattern with trace elements of polyurethane and nylon, which, along with plywood and steel bolts and chains, indicated the presence of a welding dam left inside the pipe.

A welding dam is a kind of plug used to create a small volume around a weld joint of piping, allowing argon to pressurize that gas volume to reduce oxidation during the welding process. This welding dam was fabricated from a polyurethane seal and wooden discs. Steel bolts and chains allow the welder to pull the dam out of the pipe after use.

The investigation concluded that the welding dam was left in the pipeline during its construction and ignited after the pipeline underwent startup with oxygen, pushing the welding dam through the piping until friction ignited it. Scorch marks inside the piping were observed upstream of the burn-through location, indicating the welding dam was burning as it traveled down the pipeline until it settled and its combustion energy burned through the piping at its resting place.

Incident 5: Home Oxygen Concentrator

A home healthcare patient was asleep in her bedroom breathing oxygen from an adjacent room via a long canula tube connected to this oxygen concentrator. She woke to the sound of a fire alarm and her dog barking and quickly discovered a fire coming from the concentrator. She unplugged the device and extinguished the residual fire with a cup of water.

WHA received evidence from the incident to inspect for the risk of electrical fire, but evaluation, reconstruction, and testing showed that the fire originated not from internal electrical components, but from outside the device. The likely fire path was from the canula tubing, burning back through the humidifier and into the concentrator casing.

This type of fire ultimately led manufacturers to implement “fire breaks,” or sections of burn-resistant materials, in oxygen concentrators like this one, a tangible safety feature that can be used to reduce the risk of fire propagation into the concentrator from external ignition sources, such as ill-advised smoking by users.

Helping industry stay safe around oxygen

At WHA International, we use innovative, data-driven tools to help clients understand, evaluate, and mitigate hazards and fire risks associated with oxygen, hydrogen, and other hazardous fluids. Our technical services help industries make intelligent decisions that could save lives. Incidents such as these depict the impact of real-world oxygen fire events and help us better understand their magnitude.

Every day, these stories and artifacts from our investigations help remind us at WHA why we do what we do. We hope that these incidents serve as a reminder for the need for industry best practices related to oxygen, including materials and design practices, proper cleaning, inspection, assembly, operations, and related training.

To learn more about WHA’s oxygen safety services, visit our pages for failure analysis, hazard analysis, testing, training, and cleaning.

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