In an chemical industry, a formaldehyde storage tank exploded during welding process on the outside of the wall of storage tank. This one was filled 2/3 with formaldehyde (37% solution). Inside the establishment 2 people were killed and 10 injured by the explosion. The internal emergency plan was activated. Emergency measures and protection of the public are instigated (perimeter protection, traffic disruption, containment). The contaminated area was cleaned and analytical controls for the waste water were carried out. The cost of the damages has been estimated in about 730,000 DM, inside the establishment, and about 180,000 DM outside the establishment (the explosion caused the breakage of windows).

The explosive air/formaldehyde vapours mixture in the storage tank ignited due to heat transfer supplied by a welding process. After the accident the following measures were established:

• the storage temperature to be decreased,
• the revision of the fire and explosion certificate,
• measures to match the state of the art in matter of safety,
• in the future, welding works may be performed only under an expert supervision,
• equipping of the storage tank with hermetic sealed pumps and leakage-proof fittings.