Carbon Monoxide

Carbon monoxide (chemical abbreviation: CO) is a clear, colourless gas you can’t smell or taste. It’s dangerous because it interferes with your body’s ability to use oxygen. Even in small doses, carbon monoxide can kill you. The first signs are headache and fatigue. Higher exposure can rapidly lead to loss of consciousness, arrested breathing, heart failure, and death. On a construction project you may be exposed to carbon monoxide when working around equipment and tools such as propane heaters, circular saws, compressors, scissor lifts, cement mixers, and any gasoline-, propane, or diesel-powered equipment. Exposure can be more severe when in an enclosed or confined space.

In general, every employer must take all reasonable measures necessary to protect workers from exposure to hazardous biological or chemical agents, including carbon monoxide. Measures of protection include:

engineering controls,
work practices,
hygiene facilities and practices, and
personal protective equipment.

Internal combustion engines in excavations, in buildings, or other enclosed structure must have an adequate supply of air for combustion (except for those operating in a tunnel). Exhaust gases and fumes must be discharged directly outside to a point far enough away to prevent the return of the gases or fumes. Similarly, the space must have adequate natural or mechanical ventilation to discharge exhaust and fumes so that carbon monoxide does not return or build up to hazardous levels. [O. Reg. 213/91, s.47] Internal combustion engines must be maintained in good condition so the engine’s exhaust discharge of carbon monoxide is minimized. Before using an internal combustion engine in a tunnel, a Ministry of Labour Director must give approval. [O. Reg. 213/91, s. 316]

Excavations, buildings, or enclosed structures where fuel is burnt must be to be tested for airborne concentrations of carbon monoxide to ensure the concentrations are not hazardous. Testing must be done according to a written testing strategy developed in consultation with a health and safety representative or the joint health and safety committee, if any. [O. Reg. 213/91, s. 47]

Exposure to concentrations may not exceed the time-weighted average limit (TWA)or the Short-Term Exposure Limit (STEL). These limits are defined in Regulation 833 Control of Exposure to Biological or Chemical Agents, and can be found in the table entitled “Adopted Values” shown at pages 10 to 61 of the publication entitled 2013 Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices published by ACGIH and identified by International Standard Book Number 978-1-607260-59-2.

Occupational Exposure Limits for Ontario Workplaces

Agent [CAS No.]	Time-Weighted Average Limit (TWA)	Short-Term Exposure Limit (STEL)
		For any period of 30 minutes	At any time
Carbon monoxide [630-08-0]	25 parts per million (ppm)	75 ppm	125 ppm

To determine if your workplace meets the allowable daily and weekly time-weighted average airborne concentrations of carbon monoxide, see Schedule 1 of Control of Exposure to Biological or Chemical Agents. When calculating these concentrations, any use of personal protective equipment, such as supplied air, does not alter the allowable limits of carbon monoxide to which a worker may be exposed.

Construction Projects

O. Reg. 213/91

Part II GENERAL CONSTRUCTION

Section 47

47. (1) This section does not apply to an internal combustion engine operated in a tunnel.

(2) No internal combustion engine shall be operated in an excavation or in a building or other enclosed structure unless there is an adequate supply of air for combustion and,

(a) the exhaust gases and fumes from the engine are adequately discharged directly outside the excavation, building or other enclosed structure to a point sufficiently remote to prevent the return of the gases and fumes; or

(b) there is adequate natural or mechanical ventilation to ensure that exhaust gases and fumes from the engine will not accumulate in the excavation, building or other enclosed structure.

(3) An excavation or a building or other enclosed structure in which an internal combustion engine is being operated shall be tested for airborne concentrations of carbon monoxide to ensure that the concentrations do not exceed the applicable limits as determined in accordance with section 4 of Regulation 833 of the Revised Regulations of Ontario, 1990 (Control of Exposure to Biological or Chemical Agents), made under the Act.

(4) The testing under subsection (3) shall be carried out by a competent worker in accordance with a written testing strategy, which shall be developed by the employer in consultation with the joint health and safety committee or a health and safety representative, if any.

(5) An internal combustion engine under this section shall be maintained and used in accordance with section 93.

47. No internal combustion engine shall be operated,

(a) in an excavation unless provision is made to ensure that exhaust gases and fumes will not accumulate in the excavation; or

(b) in a building or other enclosed structure,

(i) unless the exhaust gases and fumes from the engine are discharged directly outside the building or structure to a point sufficiently remote to prevent the return of the gases and fumes, or

(ii) unless there is an adequate supply of air for combustion and adequate natural or mechanical ventilation to ensure exhaust gases and fumes will not accumulate.

[O. Reg. 345/15, s. 9]

Part IV TUNNELS, SHAFTS, CAISSONS and COFFERDAMS

Section 316

316. No internal combustion engine shall be used in a tunnel on a project without the prior written consent of a Director.

[O. Reg. 145/00, s. 36]

Carbon Monoxide

Construction Projects

Part II GENERAL CONSTRUCTION

Section 47

Part IV TUNNELS, SHAFTS, CAISSONS and COFFERDAMS

Section 316

CCOHS Resources

IHSA Resources

MLITSD Resources

Carbon Monoxide

Summary

Legislation

Construction Projects

Part II GENERAL CONSTRUCTION

Section 47

Part IV TUNNELS, SHAFTS, CAISSONS and COFFERDAMS

Section 316

Resources

CCOHS Resources

IHSA Resources

MLITSD Resources