The father, his wife - both thought to be in their 40s - and their young son, aged around 12, were treated at the scene by South Central Ambulance Service for gas inhalation and taken to hospital as a precaution. No-one was seriously injured.
Firefighters used breathing apparatus to enter the plant room. They used dry earth to soak up a small amount of spilled chemical and ventilated the room. Crews from St Mary's, Redbridge and Hightown dealt with the incident.
More top news
Doors have been smashed and thousands of pounds in cash, jewellery and camera equipment taken in a spate of burglaries in Farnham, Surrey.
The forecast for the east of the ITV Meridian region from Becky.
The forecast for the west of the region from Becky.