Laboratory Explosion Due to Hydrogen Reaction in Plastic Chamber
The laboratory works with soil bacteria that cannot survive in the presence of oxygen. As a result, research work is conducted inside a plastic chamber in which the chemical constituents in the air can be controlled. The explosion occurred during the set up of one of these chambers. The chamber is essentially a plastic bag with a volume of approximately two cubic meters. The setup procedure calls for using nitrogen to purge normal atmospheric air out of the bag three times, leaving a very small amount of residual oxygen present. The remaining small amount of oxygen is then removed by reaction with hydrogen in the presence of a palladium catalyst to form water. Hydrogen was mistakenly introduced into the plastic bag as part of the first purge. As a result, the hydrogen concentration reached an explosive level inside the bag due to the relatively large presence of oxygen. The ignition source was most likely an electrical source inside the chamber or the palladium catalyst becoming too hot. The burn pattern observed after the explosion suggests that the fire ignited at the position of the catalyst, but that doesn't rule out the possibility that a spark was involved. The amount of hydrogen involved could not have exceeded one pound, which is the capacity of the compressed gas cylinder when full.
Event Date
June 28, 2010
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
Contributing factors: * Training Issue * Change in Procedures, Equipment, or Materials * Flammable Mixture in Confined Area * Lack of Hydrogen Detection Equipment
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
The hydrogen explosion occurred in a university biochemistry laboratory.The systems involved were:- Hydrogen storage equipment: gas cylinder- Process equipment: microbiological anaerobic chamber.
Storage/Process Medium
Storage/Process Quantity
0
Location Type
Location description
Inhabited Area
Operational Condition
Pre-event Summary
The laboratory works with soil bacteria that cannot survive in the presence of oxygen. As a result, research work is conducted inside a plastic chamber in which the chemical constituents in the air can be controlled. The explosion occurred during the set up of one of these chambers. The chamber is essentially a plastic bag with a volume of approximately two cubic meters. The setup procedure calls for using nitrogen to purge normal atmospheric air out of the bag three times, leaving a very small amount of residual oxygen present. The remaining small amount of oxygen is then removed by reaction with hydrogen in the presence of a palladium catalyst to form water. Hydrogen was mistakenly introduced into the plastic bag as part of the first purge. As a result, the hydrogen concentration reached an explosive level inside the bag due to the relatively large presence of oxygen. The ignition source was most likely an electrical source inside the chamber or the palladium catalyst becoming too hot. The burn pattern observed after the explosion suggests that the fire ignited at the position of the catalyst, but that does not rule out the possibility that a spark was involved. The amount of hydrogen involved could not have exceeded one pound, which is the capacity of the compressed gas cylinder when full.
Lessons Learned
Lessons Learned
Several procedural and design changes should be considered for the future:1. Replace the use of pure hydrogen with a 95:5 mixture of nitrogen and hydrogen to reduce the possibility of an explosive atmosphere occurring. Laboratory personnel should check each tank that is delivered to ensure that the gases are present in the proper ratio.2. Adhere to the manufacturer's recommendations for operation of the anaerobic chamber.3. Following the check of the lines to make sure all the connections are tight, all gas cylinders should be closed; then, only the desired gas cylinder should be opened for use.4. Use of "T" connections between gases should be eliminated. If there is continued use of a "T" connection, only connections with a toggle switch to limit the introduction of gas from a single cylinder should be used. No exceptions, even on a temporary basis.5. The laboratory should continue to investigate the availability of hydrogen and/or oxygen sensors with the hope of finding some that can withstand the corrosive atmospheric environment.6. All laboratory personnel should receive refresher training that includes standard safety precautions as well as a more detailed review of the hazards of working with hydrogen.Hydrogen use in anaerobic chambers is discussed in the Lessons Learned Corner on this website.
Event Nature
Emergency Action
First responders from the local community and the university campus were quickly on the scene. Once the injured were attended to and the site secured, response efforts focused first on assessing potential hazards (electrical, fire, hazardous materials, etc.). Campus personnel worked into the night to board up windows, isolate utility services, clean up debris, and otherwise secure the affected laboratories.
Emergency Evaluation
There were a number of factors that mitigated the damage and allowed normal building activities to resume relatively quickly:1. The laboratory group practiced good housekeeping, which minimized secondary impacts from the explosion.2. Emergency information about hazards in the laboratory was posted outside the door and was helpful to emergency responders.3. The Emergency Action Plan for the building had identified exit routes and a plan for evacuating the building in the event of an emergency. Building occupants followed the plan in a timely manner.4. During the recent remodeling of the building, utilities were reconfigured for the laboratories such that each laboratory could be isolated. This reconfiguration of utilities allowed service to the affected laboratories to be cut off while service to the remaining laboratories in the building continued to function.5. Cooperation between local first responders and campus personnel was excellent. This cooperative approach was built on a history of exercises and coordination meetings to strengthen working relationships.
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Source lost