The family of a chemical worker who died after becoming overcome by toxic fumes said today they did not believe he had flouted safety regulations.

An inquest into the death of father-of-three Derek Tuck, 41, heard how co-workers found him collapsed next to a valve emitting hydrogen cyanide at the BASF plant at Seal Sands, near Billingham, Teesside.

The production technician, who had worked at the plant for 19 years, was rushed to hospital where he was pronounced dead - just five days before Christmas in 1999.

A jury heard that each day, two-man teams took samples of the hydrogen cyanide for laboratory tests. An internal investigation concluded that Mr Tuck had probably attempted to take a sample without a colleague on standby - a procedure prohibited by BASF.

He was found with his breathing apparatus on his back, but his protective face mask, which he should have been wearing, on his chest.

More than 25 witnesses gave evidence at the three-day hearing - many of them colleagues of Mr Tuck, of Talgarth Road, Norton, Stockton.

They described him as a worker who was well aware of safety regulations and who would have known not to take a sample alone without proper equipment.

The jury returned a unanimous verdict of accidental death, concluding that "events occurred" which caused cyanide to escape into the air, overcoming Mr Tuck.

His widow Gale, 42, told The Northern Echo she could not accept that he had carried out an unauthorised procedure.

"I feel as if I'll never get to the bottom of how he died," she said. "I know he wouldn't have done anything which wasn't safe. When you live with someone for 23 years, you know them and he would never take risks.

"He knew the risks. He knew he was dealing with something that could kill him."

Health and Inspector Executive inspector Peter Hanlon confirmed that legal proceedings against BASF were being considered. "A decision will be taken shortly," he said.

A BASF spokesman said: "It has taken a long time for the coroner's inquest to take place and BASF and its employees are relieved that the cause of death has finally been determined.

"The verdict of accidental death appears to be fair given all the evidence." .