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Electrical Hazards

Safe At Work Ontario
  • Issued: November 10, 2016
  • Content last reviewed: November 2016
  • See also: Construction

Disclaimer: This resource has been prepared to help the workplace parties understand some of their obligations under the Occupational Health and Safety Act (OHSA) and regulations. It is not legal advice. It is not intended to replace the OHSA or the regulations. For further information please see full disclaimer.


Workers risk serious, life-changing injuries and possible death if they come in contact with energized conductors or equipment.

It takes very little electrical current to kill a worker. Less than one amp of electricity can cause a worker to stop breathing. Contact with a live 15-amp circuit (equivalent to a standard household 125-volt circuit) can result in death, according to the Infrastructure Health and Safety Association.

At Ontario workplaces, one in five critical injuries and one in 18 non-critical injuries involving electricity results in death, according to the Electrical Safety Authority.

Incidents can be prevented by ensuring:

  • power tools and electrical cords are properly maintained, and damaged cords and equipment are removed from service until repaired or disposed of
  • all tools and cords are grounded and/or plugged into a Ground Fault Circuit Interrupter (GFCI) protected receptacle when used in wet conditions
  • a signal person is present when operating heavy equipment around overhead electrical wires/power lines to assist operators in maintaining minimum clearance distances
  • no live work, use of proper lockout procedures, and that all equipment and conductors are de-energized or isolated
  • minimum clearance distances are maintained for overhead electrical wires/power lines when working from a ladder, elevated work platform, scaffold or other type of work platform or moving material or equipment
  • required personal protective equipment (PPE) is worn, including electric shock protective safety boots (omega sign) and Class E hard hats to reduce exposure to high voltage conductors and offer electrical protection up to 20,000 volts (phase to ground)

Employers are responsible for protecting workers from electrical hazards at construction projects.

An electrical hazard is a dangerous condition in which a worker could make electrical contact with energized equipment or a conductor and sustain an injury from shock and/or from an arc flash burn, thermal burn or blast injury.

Some common electrical hazards at construction projects include:

  • working near energized overhead conductors on a scaffold ladder or other work platform
  • moving material or tools by hand or using hoisting equipment near energized overhead power lines or live electrical equipment
  • improper grounding, electrical cords with broken ground pins, cord connected power tools without double insulated casing, and non GFCI receptacles in wet conditions
  • generators not grounded as per manufacturer’s instructions
  • no markings on the ground identifying the location of underground power lines and utilities prior to excavation
  • equipment with exposed electrical parts including missing cover plates on switches and receptacles, and missing electrical panel covers
  • inadequate wiring and wiring with damaged insulation
  • overloaded circuits, indicated by breakers "nuisance" tripping and being reset
  • equipment and vehicles being operated near energized overhead power lines

Some general duties of workplace parties

Constructors, employers, supervisors and workers have a number of duties and responsibilities under the Occupational Health and Safety Act (OHSA) and Regulation for Construction Projects. Employers and supervisors should encourage workers to communicate any questions or concerns they may have about electrical hazards. Supervisors should be familiar with and able to identify electrical hazards to workers at a construction project.


Constructors’ duties and responsibilities include:

  • ensuring workers’ health and safety is protected [OHSA s. 23(1)(c)]
  • ensuring every employer and every worker performing work on the project complies with the OHSA and its regulations [OHSA s. 23(1)(b)]


Employers’ duties and responsibilities include:

  • providing information, instruction and supervision to workers to protect their health and safety [OHSA s. 25(2)(a)]
  • taking every reasonable precaution in the circumstances to protect workers [OHSA s. 25(2)(h)]
  • ensuring equipment is operated and maintained as per manufacturer’s instructions [Construction Reg. s. 93]
  • ensuring appointed supervisors are competent [OHSA s. 25(2)(c)]
  • ensuring required equipment, materials and protective devices are provided and maintained in good condition [OHSA s. 25(1)(a) and (b)]


Supervisors’ duties and responsibilities include:

  • ensuring workers work in the manner and with the protective devices, measures and procedures required by the OHSA and its regulations [OHSA s. 27(1)(a)]
  • ensuring any equipment, protective devices or clothing required by the employer is worn/used by workers [OHSA s. 27(1)(b)]
  • advising workers of any potential or actual health or safety dangers known by the supervisor [OHSA s. 27(2)(a)]
  • providing workers with any prescribed written instructions about measures and procedures to be taken for the workers’ protection [OHSA s. 27(2)(b)]
  • taking every reasonable precaution in the circumstances for workers’ protection [OHSA s. 27(2)(c)]
  • supervising workers’ work at all times either personally or by having a competent assistant do so personally [Construction Reg. s. 14]


Workers’ duties include:

  • wearing appropriate PPE [OHSA s. 28(1)(b)]
  • using/operating equipment in a safe manner [OHSA s. 28(2)(b)]
  • reporting any defects in equipment to his or her supervisor or employer [OHSA s. 28(1)(c)]
  • working in compliance with the OHSA and its regulations [OHSA s. 28(1)(a)]
  • reporting any known workplace hazards or OHSA violations to his or her supervisor or employer [OHSA s. 28(1)(d)]
  • knowing his or her OHSA rights, including the right to refuse unsafe work [OHSA s. 43(3)(a) to (c)]

Ministry of Labour Health & Safety Contact Centre

Call toll-free 1-877-202-0008 any time to report workplace health and safety incidents Call 8:30 a.m. to 5 p.m., Monday to Friday for general inquiries about workplace health and safety.

Always call 911 in an emergency.

Disclaimer: This web resource has been prepared to assist the workplace parties in understanding some of their obligations under the Occupational Health and Safety Act (OHSA) and the regulations. It is not intended to replace the OHSA or the regulations and reference should always be made to the official version of the legislation.

It is the responsibility of the workplace parties to ensure compliance with the legislation. This web resource does not constitute legal advice. If you require assistance with respect to the interpretation of the legislation and its potential application in specific circumstances, please contact your legal counsel.

While this web resource will also be available to Ministry of Labour inspectors, they will apply and enforce the OHSA and its regulations based on the facts as they may find them in the workplace. This web resource does not affect their enforcement discretion in any way.