A routine security patrol reported a strong odor of sulfur coming from a battery charging facility. The battery charging facility is used for charging the various forklift batteries for the shipping and receiving operation. The building is approximately 450 sq. ft. and has four charging stations. Emergency response was initiated and the incident commander responded to the scene. Initial air monitoring indicated readings above the Lower Explosive Limit (LEL) for hydrogen gas. The local fire department responded and setup for the situation. Facilities personnel responded and turned power off to the building. The building was ventilated and verified to be safe by the fire department. There were no injuries or damage.

The exhaust fan for the building failed, allowing hydrogen gas to build up. A mechanical failure in the fan caused the automatic on/off sensor to overheat and shut the fan off.

The Preliminary Hazard Assessment (PHA) did not include the hazard of hydrogen buildup in the building from an exhaust fan failure. Because of this, there was no back-up exhaust system in place to keep this from becoming a problem.

The original PHA for the battery charging facility did not address the hazard of hydrogen buildup from an exhaust fan failure. The PHA will be revised to include this new information. Some additional concerns that were addressed were the addition of a vent and cooling system, a hard-wired breaker box switch, and the posting of the forklift battery charging procedures in the building. These additional concerns did not contribute to the occurrence, but were identified as improvements.

Incident Date
Apr 19, 1994
  • Ventilation System
  • Exhaust Fan
Damage and Injuries
Probable Cause
Contributing Factors
When Incident Discovered
Lessons Learned

The simplicity of this situation has made us aware that increased consideration must be given to all aspects of the workplace when preparing preliminary hazard assessments. Some hazardous situations appear so trivial that they can be easily overlooked and serious consequences not understood. Also, some hazardous situations are not readily recognized by the layman and we should consider inviting professionals from other organizations to assist us with assessments and reviews on a periodic basis.

Adequate ventilation of battery charging facilities is addressed in the Lessons Learned Corner on this website.