Hydrogen alarms went off in a research laboratory and the fire department was called, but no hydrogen leak was detected. The hydrogen system was leak-checked with helium and found to be leak-free except for a very small leak in the manifold area. The manifold leak was fixed, but because of its small size, it was not thought to be the likely source for the hydrogen alarm trigger. While hydrogen was removed from the system for leak-testing, the hydrogen alarm went off again, and again the fire department responded. There was no hydrogen present in the system to trigger this alarm. Other sources within the building were checked to see what may have set off the alarm, but none were found. One research area uses small amounts of hydrogen, but laboratory logs indicate that none was being used at the time the alarm sounded. Carbon monoxide was also being investigated as a possible alarm trigger. The cause for the alarm has not yet been determined, but the investigation continues. There were no injuries or property damage associated with this event.
The research laboratory used hydrogen to create a very pure flame for a lathe to create fiber optic cables. The pure flame is important for the vapor deposition process used in the creation of the fiber optic cables. Hydrogen cylinders (ten 300-cubic foot cylinders for a total of 3,000 cubic feet or 85,950 liters) are located on the first floor, joined together by a manifold, and then piped for use on the 5th floor of the building. A hydrogen leak-detection system with alarms is located along the hydrogen path from the manifold to the point of use. The detectors used are combustible gas detectors that are calibrated for hydrogen.
- Safety Systems
- Measurement / Sensing Device
- Hydrogen Storage Equipment
- Gas cylinder
- Laboratory Equipment
- Glass Lathe
1. Combustible gas detectors calibrated for hydrogen can falsely report hydrogen alarms due the presence of other gases the detector may pick up, such as carbon monoxide from engine exhaust or other sources. Since this event occurred, two hydrogen-specific alarms have been installed at this facility to eliminate false hydrogen alarms.
2. A building's ventilation system can be a source of gases that can trigger a hydrogen alarm, especially a combustible gas detector used for hydrogen detection. In this case, there were multiple sources of non-hydrogen gases that likely triggered the hydrogen alarm. A boiler needing maintenance that was operating near the building ventilation inlet was a possible source of non-hydrogen gas getting into the building, and it has subsequently undergone repairs to minimize the likelihood of it being a gas source. The loading dock that is partially inside of the building is used to start equipment like snow-blowers during cold weather and is also a possible gas source. Finally, when the fire department arrived with 15 fire vehicles operating near the building for 4 hours, some of the exhaust gases were likely sucked into the building ventilation system as the hydrogen alarms continued to alarm even though all the hydrogen bottles had been removed from the building by order of the fire department after the first alarm response.
3. Hydrogen storage capacity must meet storage regulations as defined by various agencies, including OSHA. Subsequent investigation by OSHA after this event found a violation in the building construction related to the 3,000 cubic feet (CF) of hydrogen being stored in ten 300-CF bottles. One cubic foot less of hydrogen storage capacity would have complied with the OSHA hydrogen storage standard for this construction type (reference OSHA regulation 1910.103(b)(2)(ii)(c) Table H-2, that has three storage capacities: less than 3,000 CF, 3,000-15,000 CF, and in excess of 15,000 CF). In this event, the building did not meet the minimum distance in feet for 3,000 CF and greater hydrogen storage, so subsequently the storage capacity was reduced by the removal to two bottles to bring the hydrogen storage capacity under 3,000 CF.
4. Personnel should follow procedures for reporting hydrogen alarms to minimize outside personnel being unnecessary activated. Procedures in place for reporting hydrogen alarms had the following three levels of action: 1) for up to 10% of the LFL, the system is to be shut down and the Safety Department (on 24-hour call) notified, 2) for above 10% to 20% of the LFL, the premises are to be evacuated and the Safety Department notified, and 3) above 20% of the LFL, the fire department is to be called. Note that above 25% of the LFL, the alarm system automatically calls the fire department. In this event, the alarm levels were below 10% of the LFL, but the fire department was notified unnecessarily by the operating personnel. The research facility and other involved entities incurred additional expenses for emergency response that could have been avoided if reporting procedures had been followed.