It caused a pounding headache, she went pale, felt nauseous, had a tight chest, developed breathing difficulties like an asthma attack and experienced high blood pressure.

Mrs Hedley saw a doctor for about two hours immediately afterward and returned to the doctor yesterday for a check-up to ensure her health had settled down.

Mrs Hedley said it was lucky she was only caught by the edge of the plume, which she saw travel over several kilometres after a 12.15am blast last Friday.

Her car was engulfed near the intersection of Putty and Wallaby Scrub roads by remnants of the fumes after waiting until she thought it had cleared before continuing to drive down Putty Road.

Mrs Hedley’s husband, Ian, said the community should be aware that such plumes could be fatal.

Mrs Hedley’s husband, Ian, said the community should be aware that such plumes could be fatal.

He pointed to an American Mine Safety and Health Administration report that says mine blasts generate potentially harmful gases such as carbon dioxide, carbon monoxide, oxides of nitrogen, ammonia and sulphur dioxide and reduce the oxygen concentration in air.

Breathing contaminated air after a blast may kill a person in a few minutes, the report says.

A report by the explosive firm Orica said the acceptable level of nitrogen dioxide in a plume was five parts per million and it turned orange-red when the concentration was between 50 and 250 parts per million and a deep red from 250 parts per million up.

State Planning Department spokesman Jim Hanna said the department had received no complaints about Friday’s red and orange plume.

As a result of an Argus inquiry, departmental officers said they would request a detailed report from the mine operator which would be checked against the mine’s approval conditions.

Questions related to the health risks of blast plumes should be referred to the state health department, Mr Hanna said.

Mount Thorley Warkworth spokesman Graham Witherspoon said company officials would conduct an internal investigation with the intent of using what was learned to reduce the potential for future incidents.

“We put in place precautionary measures before undertaking the blast, including taking into account the wind direction and closing a section of Putty Road to the public,” Mr Witherspoon said.

“Fume generated by the blast was observed to migrate in a north, north westerly direction, passing over Putty Road and dissipating at height over the Warkworth mine.

“The road was inspected by Mount Thorley Warkworth blasting personnel prior to being reopened to ensure the blast fume had dissipated and was safe for public access.”