TOXIC gas was released after a fire broke out a business housing acid.
Emergency services were scrambled to Tyre Factory at the Sunnyside Business Centre, Daubhill, at around 9.30am after fire broke out in a wooden structure inside the building.
The structure contained hydrofluoric acid, which when heated became a gas.
When inhaled the gas affected staff’s breathing and seven people were given precautionary checks by the North West Ambulance Service.
However none of them required any treatment.
It was initially feared that the acid had caused a chemical fire, but after a fire investigation it was determined to have been caused by an electrical fault.
Fire crews contained the blaze to the wooden structure and no one was injured during the incident.
They then remained on the scene until around 3pm, leaving the situation in the hands of a specialist company who handle chemical incidents.
Hydrofluoric acid is a highly corrosive chemical compound with various industrial uses, including in wheel cleaners in car washes and as a rust inhibitor.
It is also highly toxic and, when in a gas form, an acute poison which can cause immediate and permanent damage to lungs and eyes.