The seat of the fire was located in a raw materials warehouse at Allied Colloids site in Low Moor, Bradford. The warehouse itself had two rooms allocated for the storage of oxidising and flammable products known as No.1 and No. 2 oxystores. No. 2 oxystore had steam heating as it was originally designed to store frost sensitive products.
On the morning of the incident steam heated blowers in the warehouse had been turned on to dry out moisture. It is thought that a steam condensate line was responsible for heating a number of AZDN kegs, which were stored at height in the No. 2 oxystore. The heating effect caused two or three of the AZDN kegs to rupture and spill white powder all over the floor. A passing employee thought that the powder was smoke and raised the alarm. It was determined that no immediate hazard was present and the AZDN data sheet was referred to before a clean up plan was devised. While waiting for confirmation from the appropriate vacuum cleaner manufacturer an employee noticed a plume of smoke/vapour and a hissing noise coming from a bag of SPS that was located underneath the AZDN kegs. Before the employee could douse the SPS with water the vapour plume ignited and became a jet flame of about 300 mm in length. Within a few seconds the jet flame became a flash fire which was transmitted all around the room.
It was determined later that the AZDN powder probably mixed with unintended spills of SPS and other oxidising products. AZDN in contact with SPS is likely to have been ignited by an impact, possibly from a lid and associated metal ring closure from one of the damaged AZDN kegs falling onto a bag or the floor.
The fire spread throughout the warehouse and smoke was blown towards nearby motorways. The fire was contained that day and the fire brigade was not stood down until 18 days later due to risk of re-ignition during clean up. Considerable environmental damage to the Aire and Calder rivers resulted from the firewater run off.
Health and Safety Executive, ‘The fire at Allied Colloids Limited. A report of the HSE’s investigation into the fire at Allied Colloids Ltd, Low Moor, Bradford on 21 July 1992’, ISBN 0 71 760 707 0, 1993.