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.
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Oxford's most famous hotel, the Randolph, is ablaze after a fire started in the roof space. 12 fire crews are on location in the city.
Friday night's weather for the east of the region
Friday night's weather for the west of the region