This Current Intelligence Bulletin briefly discusses the explosive hazard associated with sodium-azide (26628228). Sodium-azide, a common preservative used in automatic blood counters in over 15000 hospitals and clinical laboratories in the United States, was associated with a number of violent explosions at hospitals in the United States and Canada. These were due primarily to azides accumulating in the drains and plumbing. After completing the blood count procedure, the waste (containing azide) was usually flushed into a drain, bathing the drain with solutions of sodium-azide. Over a period of time, the azide reacted with copper, lead, brass, or solder in the plumbing system to form an accumulation of lead- azide (13424469) or copper-azide (14215306). It is noted that both lead-azide and copper-azide are more explosive than nitroglycerin and more powerful detonating agents than mercury-fulminate; copper- azide is too sensitive to be used commercially. Future accumulations of lead-azide and copper-azide can be retarded by thoroughly flushing the drains with copious amounts of water several times a day. Use of plumbing free of lead or copper or of reagents that do not contain azides are recommended. Procedures for decontaminating plumbing that currently contain explosive azides are given. These involved the use sodium-hydroxide or nitrous-acid.