Hamilton Sheriff Court heard how Thomas Fraser,37, died in an on-site flat used as a base for workers at the site in Ann Street, Burbank run by Clyde Valley Housing.
Alpha Group Security of Glasgow was fined £7000 by the court following the tragedy in February 2008.
The court heard a portable power generator was used inside the flat but Fraser had not been provided with proper instructions on its safe use.
The generator was operated without appropriate ventilation and Fraser was overcome by a build up of carbon monoxide fumes and died.
Following the case, HSE Inspector Adrian Tinson said: “This tragic incident should never have happened. It is the clear duty of those who create risks to manage them and to implement safe systems of work.
“This means clear instructions should be provided to contractors and operators and checks made to ensure they understand them.
“It should not be assumed that someone knows how to operate equipment. Responsible management of risk should have ensured the safe set up and use of the portable petrol generator in a well-ventilated area which could have avoided this unnecessary death.”
In March 2010, Clyde Valley Housing, which subcontracted Alpha Group Security Ltd, was fined £70,000 after pleading guilty to a charge under the Health and Safety Act.