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can also decompose trichloroethylene and perchloro-ethylene 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:

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

material;

2. Misuse of compressed gases and cylinders.

3. 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

goggled operator.

To prevent fires and explosion: keep equipment clean and operable, free of oil,

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

combustibles are in the 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, ventilators. If the work

cannot be moved, move combustibles away from sparks and heat; or protect against

ignition with suitable fire- resistant covers or shields.

Walls, ceilings, and floor near work should be protected by heat resistant covers or

shields. Fire watcher must be standing by with suitable fire extinguishing equipment

during and for some time after welding or cutting if:

1. Appreciable combustibles (including building construction) are within 10m.

2. Appreciable combustibles are further than 10m, but can be ignited by sparks.

3. Openings (concealed or visible) in floors or walls can expose combustibles to

sparks.

4. Combustibles adjacent to walls, ceilings, roofs or metal partitions can be ignited

by radiant or conducted heat.

After work, check that 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.