WorkSafeBC Home

Worker died when overcome by carbon monoxide in confined space

Date of incident: December 2021
Notice of incident number: 2021116110028
Employer: Construction company

Incident summary
A worker attended a worksite — a house under construction — outside of work hours to refuel a gas-powered generator that was operating in the unfinished basement. The worker was overcome by carbon monoxide in the enclosed basement and died.

 

Investigation conclusions

Cause

  • Combustion in confined space led to high carbon monoxide levels. During extreme cold weather, the employer was operating a gas-powered generator in the unfinished basement of the house it was building. The generator was being used to power an electric space heater to prevent frost damage to the recently poured foundation. The employer had enclosed the unfinished basement, covering all the window openings to keep the heat in, thereby creating a confined space. Fresh air could not enter the space, and exhaust from the generator could not leave the space, allowing hazardous levels of carbon monoxide (CO) to accumulate.

Contributing factors

  • Ineffective safety management program. An effective safety management program provides the ability for an employer to correct unsafe conditions and practices. An effective safety management program was not being used by the employer at the time of the incident.
  • Failure to conduct a hazard assessment and implement controls. The employer did not conduct a hazard assessment, which would have identified the potential for harmful levels of CO to accumulate in the unfinished basement. With an adequate assessment, the hazard would likely have been better understood and controls identified to eliminate or reduce workers’ exposure to harmful levels of CO. Installation of a temporary construction power supply for the electric space heater would have eliminated the need for the generator, and alternative methods of providing power or heating from outside the basement would have prevented the accumulation of harmful levels of CO in the basement.
  • Extreme cold weather. The extreme cold weather threatened to damage the foundation of the house. The employer enclosed the basement to heat it and protect the foundation from frost heaving. Using a gas-powered generator to power the electric space heater in the enclosed basement resulted in the accumulation of hazardous levels of CO.
  • Failure to follow manufacturer’s instructions. Contrary to the manufacturer’s instructions, the employer operated the generator in the fully enclosed unfinished basement. Had the generator been operating outdoors, harmful levels of CO would not have accumulated in the basement.

Request the full report

Publication Date: Jan 2025 Asset type: Incident Investigation Report Summary NI number: 2021116110028