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*                               ALERT                               *
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*  Produced by:  Ontario Ministry of Labour                         *
*  Provided by:  Canadian Centre for Occupational Health and Safety *
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INFO ALERT:  C3/0993

DATE:  09/93


*** HAZARD SUMMARY:  EXPLOSION - SEWER CONSTRUCTION USING A LASER
DEVICE ***  

During the investigation of an explosion at a sewer repair project the
ignition source was found to be the battery connection for the
project's laser alignment device.  Both laser and battery had been
located in a manhole.  Natural gas, seeping through the soil from a
damaged temporary plastic gas line, was ignited by a spark from the
battery connection.  In the resulting explosion a worker was badly
burned.

A battery inside a manhole, and not remote from it, may be a hazard. 
The laser manufacturer's written instructions apparently do not
address battery location.


*** LOCATION(S) AND SECTOR(S): ***

Construction of underground piping systems.  Also work in existing
sewer manholes when tying into existing sewer lines which are
considered a confined space.


*** SUGGESTED PRECAUTIONS: ***

The battery for a laser device should be located far enough from the
manhole or sewer pipe to ensure that it will not act as an ignition
source for explosive hazards originating in the excavation or in
existing sewer lines.  Extra-length conductors may be required and are
available.


*** FURTHER ACTION: ***

The Regulations for Construction Projects, Ontario Regulation 213/91,
will be reviewed for possible amendments to address the use of
explosion-proof connections in confined spaces.



Produced by the Construction Health and Safety Program, Occupational
Health and Safety Branch, Ministry of Labour.


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