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Case No.9

Electrocuted while removing dust in the electrical distribution room of a hotel

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[Circumstances of Incident]

This accident occurred in the electrical distribution room of a hotel where a chief electrical engineer was electrocuted near the place where disconnecting switch was mounted. A building maintenance company had dispatched the engineer on the basis of a cleaning and maintenance contract for various equipment and facilities in the hotel.

The hotel had been closed for three days for the inspection and improvements of boilers, the replacement of tatami mats in the guest rooms and upgrading the bathrooms.

The victim arrived at the underground machine room of the hotel at around ten o'clock in the morning to observe test of the boilers on which maintenance work had been completed the previous day. At around 10:30, he entered the electrical distribution room after telling colleague from the same company that he intended to "remove some dust" from electrical equipment near the entrance of the room isolated by wire netting.

At about eleven o'clock, a loud cracking sound was heard from the room, the power was suddenly suspended and an alarm started to ring. When workers working in the machine room rushed to open the door of the electrical distribution room, they found smoke filling and could see the victim's legs on the floor.

The victim had fallen to the floor with his head between an instrument transformer and a power transformer. Carbonized pieces of fabric were scattered around the engineer's body and a bamboo stick was found nearby to which a small piece of cloth was attached.

In the electrical distribution room, three exposed edges of the secondary side disconnector for the instrument transformer were not opened. Metal fittings attaching the disconnector edges were fused and broken, and black burn marks were found on the frame pipes supporting the disconnector. 


The following can be cited as the causes of this accident.

Some 30 minutes before the accident, the victim had told the boiler operators resident in the hotel that he intended to dust electrical equipment. He is believed to have entered the electrical distribution room to which access was prohibited for others, used a bamboo stick to remove dust from various electrical units, and was accidentally electrocuted when he came too close to portions carrying a high-voltage charge (6,000 volts).

As the victim was an experienced electrical engineer with the class-III chief electrical engineer qualification, it is not certain why he entered the electrical distribution room without first tripping the high-voltage circuit breaker that could be operated from outside the room. He is assumed to have incorrectly assumed that the power supply to the electrical room was suspended as boilers had been stopped and were under inspection. In addition, he may have been unfamiliar with various conditions in the electrical room as he was dispatched only on a temporary basis, and may also have mistakenly believed that the bamboo stick used to remove dust was a safe tool.    

[Type of business] Building maintenance industry
[Type of accident]Electric shock
[Number of victims] One fatality