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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Increasingly cloudy with drizzly rain tonight. A cloudy start on Monday but brightening up with plenty of sunny spells in the afternoon.
The grass pollen risk will rise to high during warm, dry weather.
Cloudy with patchy rain and drizzle this evening. Mild tonight, then dry with plenty of sunny spells tomorrow.