Date of incident: August 2024
Notice of incident number: 2024199260002
Employer: General contractor

Incident summary
A worker was using a gas-powered cutter (saw) to cut an empty water pipe located in an excavation approximately 3.7 m (12 ft.) deep. The type of work being performed in the excavation meant the excavation was also a confined space. The worker felt unwell and climbed out of the confined space. First responders attended the worksite and transported the worker to hospital.

Investigation conclusions

Cause

• Exposure to carbon monoxide (CO) in confined space. The worker entered the excavation, which was classified as a confined space, and used the gas-powered saw to cut the pipe. The worker was exposed to CO and other air contaminants from the saw’s exhaust.

Contributing factors

• Inadequate hazard identification and risk assessment. The employer did not adequately assess the level of risk posed by working in a confined space with a gas-powered saw. A confined space entry permit for work in the excavation had been filled out, but in the pre-work meeting on the morning of the incident, the excavation was not identified to workers as a confined space. In addition, the atmosphere in the confined space was classified as being low hazard when in fact using the saw in the excavation created a high-hazard atmosphere in it. Therefore, the work posed a high risk of injury or death to workers.
• Inadequate ventilation. The confined space that the worker was working in was a high-hazard atmosphere that required continuous ventilation from a mechanical system. The system was to be designed, installed, and maintained in accordance with established engineering principles and was to be specified in written procedures. The employer did not provide such a mechanical ventilation system.
• Inadequate training.
  • The worker was not sufficiently informed, instructed, or trained with regard to the hazard of CO emissions when using a gas-powered saw to cut a pipe in a confined space.
  • The employer’s workers had completed confined space training just over three years before the incident; however, they were not trained specifically on the employer’s confined space program.
• Inadequate supervision. The employer did not ensure that the level of risk to the worker posed by his work in the excavation was adequately assessed by a supervisor at the site, nor were adequate controls implemented to lessen the risk.
• Failure to follow safe work procedures. The safe work practice for confined space created by the employer was not followed by the workers. The worker was not wearing adequate PPE and the work area was not identified as a confined space. The work zone was also incorrectly identified as a low-hazard atmosphere in the confined space entry permit. The air was not monitored after the initial pre-work reading and the worker was exposed to CO because of using the gas-powered saw in the confined space.
• Failure to follow manufacturer’s instructions.
  • The manufacturer’s instructions for the gas-powered saw the worker was using identify the dangers of CO and the need to use the saw in a well-ventilated area. The manufacturer’s instructions to safely use the saw were not followed.
  • The manufacturer’s instructions for the half mask and accompanying filter the worker was wearing state that they are not to be used in a confined space environment without adequate ventilation and do not offer protection against CO. The manufacturer’s instructions for the mask and filter were also not followed.

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