Three Sheffield workers were almost overcome by fumes when a decontamination unit began to fill with deadly carbon monoxide, a court heard.

The men were part of a five-strong team working in an asbestos enclosure on a demolition site in Huddersfield in November 2009. After working for 90 minutes, each left the enclosure to go one at a time through a three-stage decontamination unit (DCU).

The Health and Safety Executive (HSE) prosecuting told the court the first two workers passed through each of the stages successfully but the next three men were nearly overcome by dizziness and nausea.

The three workers, Richard McKearnen, 59, Tony Deakin, 50, and Paul Wainwright, 49, all from Sheffield, were sent to hospital, where tests showed they had suffered carbon monoxide poisoning. .

The DCU used a gas boiler to provide hot water for the shower, tests on the boiler showed it was pumping out high levels of carbon monoxide. In addition, a door seal and lock between the boiler compartment and ‘clean’ sections of the unit were damaged, leading to poisonous gases being drawn into the clean end. company was fined £5,000 and ordered to pay £3,580 in costs.

Inspector David Stewart, who investigated the case for the HSE, said:

“Carbon monoxide can be a silent killer in the home and, as this case demonstrates, also in the workplace. It is essential that any appliances such as gas boilers and heaters, which can generate this gas, are maintained on a regular basis to ensure they are operating efficiently and safely.

“Even though these three men spent a relatively short time in the affected part of the decontamination unit, they were left seriously nauseous and dizzy. The consequences of longer exposure could have been fatal.