A researcher in one of our scientific divisions was operating an automatic film processor controlled by an electric timer. She attempted to override the device to extend the processor’s operating time by opening up the timer and resetting its "off screw clip". The metallic off screw clip made contact with a 120 volt energized circuit below the timer dial which created an electric arc. The photograph, located below, shows charring below the dial. The employee received second and third degree burns on the thumb, index and middle fingers of her left hand. (This accident could have had far more serious consequences: 120 volts is well into the lethal range.) Moreover, sparks from the disintegrated off screw clip had caused some paper towels on the floor to smolder.

A contributing factor to this accident was the absence of the manufacturer installed shield used to cover the energized portion of the timer. In fact, the timer was moved from a different location and installed without its protective shield in place. Furthermore, even though several users questioned the device’s safety, they never reported it. The lesson we can all learn from this event is that if you can touch the conducting parts of any type of electrical equipment, or make contact with a conducting medium (such as a tool), it is a hazardous condition. You should alert others not to use it and report the condition to your supervisor for corrective action. In the interim, the equipment should be locked and tagged out as unsafe to use.

A co-worker called 7911 and extinguished the smoldering paper towels. Upon arrival, the Fire Department attended to the injured employee, inspected the dark room to ensure that the fire was completely extinguished and locked out the unsafe timer. The employee was transported to the Alta Bates Emergency Room and was treated and released. The EH&S Electrical Safety Engineer issued an alert to identify and correct similar installations.

If you should have any questions regarding this event or any electrical safety issue, please contact Tom Caronna of EH&S, at extension 4314.