Preparation for a school chemistry lesson went awry when the fan on a fume cupboard – designed to limit exposure to hazardous or toxic fumes – broke, sparking a 999 call.
Crews from Blackpool and South Shore fire stations were called to a lab at St George’s School, in Cherry Tree Road, Marton, by staff.
Wearing breathing masks and gloves, they neutralised a quantity of acidic chemical bromine, which was contained inside the fume cupboard, before using fans to clear the lab of fumes, Lancashire Fire and Rescue service spokesman John Taylor said.
Nobody was hurt during the incident, which happened when the school was closed at 4.50pm on Wednesday.
Inhaling bromine fumes can cause breathing problems, headaches, mouth and nose irritation, and watery eyes, while coming into contact with bromine liquid can cause burns.
Mr Taylor said: “The classroom was emptied and shut off as a precaution but there was no evacuation. It was contained.”
St George’s, which is run by Christian sponsor Cidari, teaches chemistry as a GCSE option for its Key Stage Four students.
Bromine is often used by schools and colleges in demonstrations because it reacts ‘spectacularly’ with metal, the Royal Society of Chemistry said.
On its website, the society said flames and coloured smoke is produced when bromine – itself a non-metal – reacts with aluminium.
“These experiments must be done in a fume cupboard as both the reactants and products are hazardous,” it said.
St George headteacher Daniel Berry, set to be replaced by deputy head Graham Warnock when he takes the helm at Kirkham Grammar School in April, said: “A science technician was working after school in the lab.
“We had a problem in the science prep room with a faulty fan.
“Protocol deems we have to report this to the fire brigade.
“Children had left and the school was closed. The fan is now being replaced.”