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perchloroethylene vapours to form phosgene. DO NOT WELD or cut where

solvent vapours can be drawn into the welding or cutting atmosphere or

where the radiant energy can penetrate to atmospheres containing even

minute amounts of trichloroethylene or perchloroethylene.

C) FIRE AND EXPLOSION PREVENTION

Causes of fire and explosion are:

•

Combustibles reached by the arc, flame, flying sparks, hot slag or

heated material.

•

Misuse of compressed gases and cylinders.

•Short circuits.

BE AWARE that flying sparks or falling slag can pass through cracks, along

pipes, through windows or doors, and through wall or floor openings, out of

sight of the goggle wearing operator.

To prevent fire and explosion, keep equipment clean and free of oil, grease,

and (in electrical parts) of metallic particles that can cause short circuits. If

combustibles are in area, do NOT weld. Move the work, if practicable, to an

area free of combustibles.

Avoid working in paint spray rooms, dip tanks, storage areas and ventilators. If

the work cannot be moved, move any combustibles away from sparks and

heat or protect against ignition with suitable fire-resistant covers or shields.

Walls, ceilings and floors near the work should be protected by heat resistant

covers or shields. A Fire Watcher must be standing by with suitable fire

extinguishing equipment during and for some time after welding or cutting if:

•

appreciable combustibles (including building construction) are

within 10m.

•

appreciable combustibles are further than 10m, but could be ignited

by sparks.

•

openings (concealed or visible) in floors or walls exist, which could

expose combustibles to flying sparks.

•

combustibles adjacent to walls, ceilings, roofs or metal partitions

could be ignited by radiant or conducted heat.

After work, check that the area is free of sparks, glowing embers and flames.

An empty container that held combustibles or that can produce flammable

or toxic vapours when heated, must never be welded on or cut, unless the

container has first been cleaned. This includes a thorough steam or caustic

cleaning (or a solvent or water washing, depending on the combustible’s

solubility) followed by purging and inerting with nitrogen or carbon dioxide

and using protective equipment.

Water filling just below the working level may substitute for inerting.