BURNABY, B.C. — Three men who died at a Fraser Valley mushroom farm after being overcome in a shed by a mix of toxic gases, despite repeated warnings from workplace safety authorities, didn't have to die, a coroner's inquest has been told.

Coroner's lawyer Chris Godwin said in his opening statement at the inquiry that the deaths and injuries to three other men might have been averted if the workers had known the risk and the company had put the proper safety procedures in place.

"Mr. Coroner, this was a tragedy that perhaps could have been prevented," Godwin said.

Jurors heard one man went into a shed that day in September 2008 and was overcome by a mix of toxic gases. The others followed to try to help him.

What followed was chaos made more difficult by the fact that the workers spoke only Vietnamese and the rescuers only English.

Paramedic Vincent Ford was the first on the scene of what he thought was a drowning. Instead, he had to declare the area hazardous and said he spent his time until firefighters arrived trying to keep the farm's remaining staff from trying to enter the shed to conduct a rescue themselves.

"They were pretty perturbed at us for not going into the shed," he said.

Ford said he had only recently taken a course about poisonous gases in confined spaces after two paramedics died in a B.C. mine accident.

Ford's partner that day, Matthew Nasseri, told the inquest the worst part about the call is he and Ford couldn't go in to help but because of the language barrier, and they couldn't explain their decision.

"I think it will stay for us for the rest of our lives," he said. "We were helpless. We couldn't do anything."

B.C.'s workers compensation board concluded in a report last November that the owners of the mushroom farm had been repeatedly warned that a composting system was potentially dangerous.

The report concluded a deadly combination of flawed design and inadequate safety procedures caused the deadly accident. Besides the three workers who were killed, two others were left with serious brain injuries.

The report found the accident happened as workers were attempting to clear a clogged water pipe. A mix of toxic gasses leaked into the small shed they were in.

WorkSafeBC's 61-page investigative report detailed years of failures and ignored warning signs that culminated in the deadly accident.

The site included a compost facility that converted chicken manure, straw, gypsum and water into fertilizer, which was then used on the mushroom farm.

The water used in the compost process was collected from sources around the farm and was also recycled from the composting system itself.

The report found the problems dated back to 2005 with the construction of the water recycling system, which didn't include measures to keep straw and other materials from entering its tanks and pipes.

It also stored so-called brown water in a very large holding tank, which allowed water to remain in the tank longer and meant straw and sludge settled at the bottom.

It was that straw and sludge that clogged the pipe and the stagnant water that allowed hydrogen sulphide and carbon dioxide, the gasses that suffocated the workers, to form, the report concluded.

In 2007, a small shed was built over a set of pumps and pipes to keep them from freezing in the winter.

The leak occurred inside that shed, which was a dangerous confined space that allowed gasses to quickly reach fatal levels and complicate rescue efforts. Management of the farm didn't recognize the shed as a confined space, and didn't put in place the required safety measures or training, the report found.

There were a number of signs in the year leading up to the accident that should have prompted changes, but didn't, the report concluded.

The facility was shut down for bylaw infractions in 2007. It re-opened later that year at partial capacity, but the water recycling system continued operating at full capacity.

Also last November, a judge imposed fines of $350,000 on two companies, A1 Mushrooms and HV Truong, and their three owners, who pleaded guilty.

The dead workers were Ut Tran, Jimmy Chan and Ham Pham.