Fire and explosions ripped through a chemicals storage area operated by Grosvenor Chemicals at Linthwaite, near Huddersfield, in the early hours of 24 May.
West Yorkshire Fire and Rescue Service sent 25 fire engines to the blaze at 1am. The store contained pesticide and glue chemicals. The fire was brought under control later in the day.
Residents were advised to stay indoors and close windows as thick smoke engulfed the area.
The Environment Agency deployed its emergency Air Quality Cell for the first time since its formation after the 2005 Buncefield explosion. The team includes multidisciplinary experts from the Health Protection Agency, the Met Office and the Food Standards Agency.
The team monitored the smoke as it drifted towards Huddersfield. It later said there was no cause for concern.
Meanwhile, the Environment Agency warned that the river Colne had visible pollution and dead fish in the river. The fire service said most of the fire water was contained on-site but some may have entered the river via drainage systems.
The facility is a high-level site regulated under the Control of Major Accident Hazards legislation. The Health and Safety Executive is investigating the incident.
It is reminiscent of the 1992 Allied Colloids fire in Bradford which caused major pollution of the river Calder (ENDS Report 211, pp 3-4).
Grosvenor, part of the Whyte Group, is a contract chemicals maker producing pesticides and adhesives.
It was prosecuted in 2007 for running a chemical process without the required emission abatement system (ENDS Report 391, pp 61-62). The incident occurred despite the firm’s accreditation to the ISO 14001 environmental management system standard.