Two construction companies in Ontario have been fined a combined 85,000 Canadian dollars after workers in a parking garage in Toronto (Canada) were exposed to carbon monoxide from petrol-powered concrete finishing machines. Both companies did monitor the air quality, but according to the Ministry of Labour not adequately.
What happened
The incident took place on 4 July 2023 during the construction of a new car dealership at 5868 Yonge Street in Toronto, Ontario. The project included a three-level parking garage. Metro Concrete Works [2016] Inc. had been hired as a subcontractor by the general contractor Fieldgate Construction Management Inc. to apply a layer of concrete of about three inches (roughly 7.6 centimetres) over the structural concrete floor.
Workers finished the concrete with hand tools and with petrol-powered finishing machines. When a Metro worker and several others began to feel unwell, the emergency services were alerted. Paramedics treated several workers for exposure to carbon monoxide. The Toronto Fire Services later found elevated carbon monoxide levels in the garage and began ventilating the building. Initial air measurements showed that workers had been exposed to concentrations above the applicable limit values.
Findings
An investigation by the Ontario Ministry of Labour found that on level P2 of the garage, where the petrol-powered machines were running, the concentration of carbon monoxide in the air was not properly measured. This is required under Ontario Regulation 213/91, the regulation for construction projects.
Both companies pleaded guilty under the Occupational Health and Safety Act. Fieldgate was convicted because, as the general contractor (constructor), it failed to ensure that prescribed measures and procedures were carried out. Metro was convicted separately because, as an employer, it failed to ensure compliance with the same regulation. The case thus places responsibility with both parties.
A Justice of the Peace of the Provincial Offences Court in Toronto imposed the fines on 28 August 2026: 55,000 dollars for Fieldgate and 30,000 dollars for Metro. On top of this comes the mandatory victim fine surcharge of 25 percent, which the Provincial Offences Act prescribes.
Recommendations
The source report does not mention any specific recommendations. The case does show, however, that monitoring only helps if measurements are taken at the place where the source of carbon monoxide is located. In this case there was monitoring, but not in the area where the petrol machines were used.
Context
The IHSA, a construction health and safety organisation in Ontario, points out that on construction projects carbon monoxide is released by petrol-, propane- and diesel-powered equipment, and that exposure is greater in confined or enclosed spaces. Excavations, buildings or enclosed structures in which fuel is burned must be tested for carbon monoxide concentrations in the air, and there must be sufficient natural or mechanical ventilation. According to the IHSA, carbon monoxide has a time-weighted average (TWA) limit value of 25 ppm, a short-term value of 75 ppm over 30 minutes and a ceiling value of 125 ppm.
For HSE professionals worldwide the lesson is broadly applicable: combustion engines in a garage, basement or other poorly ventilated part of a building call for measurement at the location of the source, for sufficient ventilation and for clear agreements between general contractor and subcontractor about who checks what.
Source: Canadian Occupational Safety: Ontario construction firms fined $85,000 over carbon monoxide exposure, 6 October 2026
Additional research: IHSA: Carbon monoxide (OHS Guide)
