Explosive azide salts may occur when there is contact with:
(1) copper (including brass)
(2) lead (including solder)
Explosions may occur with:
(1) vibration
(2) friction
(3) heat
(4) exposure to strong light
Metal azide salts may develop in hospital plumbing if solutions containing azide preservative is disposed in a sink for a prolonged period. Explosions have occurred when plumbers have:
(1) tried to pass a plumber's snake past a clog
(2) removed a sink trap
(3) cut piping
The best prevention is to use a non-azide preservative. If no alternative is available, then the lowest effective concentration of sodium azide should be used. Azide buildup can be prevented by either flushing the plumbing with large amounts of water while disposing of azide-containing solutions or by using non-metal plumbing.
If a plumbing system is believed to be contaminated with azide salts:
(1) the piping can be treated several times with 10% sodium hydroxide solutions that is left in contact for 16 hours
(2) if the plumbing consists of copper or brass pipes, then additional treatment with nitrous acid for 24 hours should be done
(3) even after these treatments explosive azides may be present. Plumbers should:
(3a) Carefully remove or flush away any residual caustic solution.
(3b) Remove everything from around the sink that could become a missile or be flammable.
(3c) Evacuate the area.
(3d) Work carefully from behind a shield.
(3e) Work as far away from the piping as possible.
