Prosecutors are not asking for jail time for the owners of a Langley mushroom farm where three workers were killed and two more seriously injured after an accident three years ago.

The workers died when they were overcome by a toxic gas in a composting shed in September 2008. The operators face no criminal charges in connection with the incident, and were instead charged under the Workers Compensation Act and Occupational Health and Safety Regulations.

At a sentencing hearing in Surrey Friday, Crown prosecutors asked for heavy fines but stopped short of recommending prison time.

"This is not a case in which there was evidence that the defendants had recognized there was a hazardous situation, had ignored, and continued," Crown spokesman Neil McKenzie said.

Families of the dead and injured told reporters outside the court that they were hoping for jail time for those they hold responsible.

"At the end of the day, they go home, we go home, and all they have to do is pay fines, which they most likely will not be paying because they declared bankruptcy. I don't really understand why I'm here right now if I don't get any justice for my father," said Tracey Phan, the daughter of one of the brain-damaged men.

"I can't express to you how hard it is to go through life without someone that you used to wake up to every single day."

BC Federation of Labour President Jim Sinclair agreed that fines aren't enough.

"We know that fines are not a deterrent, or this wouldn't have happened," he said.

Details of what happened during the tragedy were revealed for the first time during Friday's hearing.

Crown lawyers say two workers were told to unclog a pipe, but were overcome by noxious fumes and died. Three others came to their aid, but one of the would-be heroes died and the others suffered permanent brain damage.

Tracey's father Michael Phan remained in a coma for almost three years, while the other man lost his hearing and ability to speak. The five men killed or brain-damaged in the incident left behind 13 children.

Investigators have said that on the day of the disaster, a pipe carrying a compost mixture broke, releasing the fumes.

The farm had been the subject of workplace complaints in 2005, and two years later, operations were temporarily shut down.

Ha Quan Truong, Van Thi Truong, Thinh Huu Doan and two companies, A-1 Mushroom Substratum Ltd. and H.V. Truong Ltd., entered surprise guilty pleas to 10 of 29 charges against them in May.

Those charges include failure to have a safety program in place and failure to educate the workers. The operators face a maximum fine of $600,000 and up to six months in jail.

The BC Federation of Labour is calling for a separate coroner's inquest to determine exactly what went wrong.

The sentencing hearing is scheduled to continue next week.

With a report from CTV British Columbia's Bhinder Sajan