OSHA construction electrical safety study guide
OSHA's electrical rules for construction work are in 29 CFR Part 1926, Subpart K (Electrical). This guide sets out what the federal rule text states on the parts a construction worker meets most: ground-fault protection, temporary wiring, flexible cords, guarding of live parts, working near circuits and tagging circuits. Every point links to the rule text it comes from, with the exact words quoted.
Scope of Subpart K
Sections 1926.402 through 1926.408 hold the installation safety rules for electrical equipment and installations that provide power and light at the jobsite. They apply to both temporary and permanent installations used on the jobsite, but not to existing permanent installations that were in place before the construction activity started.
“Sections 1926.402 through 1926.408 contain installation safety requirements for electrical equipment and installations used to provide electric power and light at the jobsite. These sections apply to installations, both temporary and permanent, used on the jobsite; but these sections do not apply to existing permanent installations that were in place before the construction activity commenced.”
Sections 1926.402 through 1926.408 do not cover installations used to generate, transmit and distribute electric energy (including related communication, metering, control and transformation installations), but they do cover portable and vehicle-mounted generators that power equipment used at the jobsite. Construction of power distribution and transmission lines is in Subpart V.
“Sections 1926.402 through 1926.408 do not cover installations used for the generation, transmission, and distribution of electric energy, including related communication, metering, control, and transformation installations. (However, these regulations do cover portable and vehicle-mounted generators used to provide power for equipment used at the jobsite.) See subpart V of this part for the construction of power distribution and transmission lines.”
General requirements for equipment
All electrical conductors and equipment must be approved.
“All electrical conductors and equipment shall be approved.”
In Subpart K, "approved" means acceptable to the authority enforcing the subpart, which is the Assistant Secretary of Labor for Occupational Safety and Health.
“Approved. Acceptable to the authority enforcing this subpart. The authority enforcing this subpart is the Assistant Secretary of Labor for Occupational Safety and Health.”
The employer must make sure electrical equipment is free from recognized hazards that are likely to cause death or serious physical harm to employees.
“The employer shall ensure that electrical equipment is free from recognized hazards that are likely to cause death or serious physical harm to employees.”
All splices, joints and free ends of conductors must be covered with insulation equivalent to that of the conductors, or with an insulating device designed for the purpose.
“All splices and joints and the free ends of conductors shall be covered with an insulation equivalent to that of the conductors or with an insulating device designed for the purpose.”
Working space and guarding of live parts
For equipment operating at 600 volts, nominal, or less, sufficient access and working space must be provided and maintained around all electric equipment so it can be operated and maintained readily and safely.
“This paragraph applies to equipment operating at 600 volts, nominal, or less. (1) Working space about electric equipment. Sufficient access and working space shall be provided and maintained about all electric equipment to permit ready and safe operation and maintenance of such equipment.”
Except as required or permitted elsewhere in Subpart K, the working space in the direction of access to live parts at 600 volts or less that are likely to need examination, adjustment, servicing or maintenance while alive must be no less than the depths in Table K-1, and at least 30 inches wide in front of the equipment.
“Except as required or permitted elsewhere in this subpart, the dimension of the working space in the direction of access to live parts operating at 600 volts or less and likely to require examination, adjustment, servicing, or maintenance while alive shall not be less than indicated in Table K-1. In addition to the dimensions shown in Table K-1, workspace shall not be less than 30 inches (762 mm) wide in front of the electric equipment.”
Working space required by Subpart K may not be used for storage. When normally enclosed live parts are exposed for inspection or servicing, a working space in a passageway or general open space must be guarded.
“Working space required by this subpart shall not be used for storage. When normally enclosed live parts are exposed for inspection or servicing, the working space, if in a passageway or general open space, shall be guarded.”
Except where Subpart K requires or permits otherwise, live parts of electric equipment operating at 50 volts or more must be guarded against accidental contact by cabinets or other enclosures, or by one of the listed means. Two of them: location in a room, vault or similar enclosure accessible only to qualified persons, or partitions or screens arranged so only qualified persons can reach the space within reach of the live parts.
“Except as required or permitted elsewhere in this subpart, live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by cabinets or other forms of enclosures, or by any of the following means: (A) By location in a room, vault, or similar enclosure that is accessible only to qualified persons. (B) By partitions or screens so arranged that only qualified persons will have access to the space within reach of the live parts.”
The other listed means of guarding live parts at 50 volts or more: location on a balcony, gallery or platform elevated and arranged to keep out unqualified persons, or elevation of 8 feet or more above the floor or other working surface, installed to keep out unqualified persons.
“(C) By location on a balcony, gallery, or platform so elevated and arranged as to exclude unqualified persons. (D) By elevation of 8 feet (2.44 m) or more above the floor or other working surface and so installed as to exclude unqualified persons.”
Not covered here
We do not cover the working-space depths for equipment over 600 volts (Table K-2), elevations of unguarded parts over 600 volts (Table K-3) or the design rules for hazardous (classified) locations and special systems, because they are installation design details beyond this guide's focus on what a construction worker needs. We only write what an official source states, so study these parts with your certifying program's materials.
Ground-fault protection (GFCI or assured grounding program)
To protect employees on construction sites, the employer must use either ground-fault circuit interrupters (GFCIs) as set out in 1926.404(b)(1)(ii) or an assured equipment grounding conductor program as set out in 1926.404(b)(1)(iii). These requirements are in addition to any other requirements for equipment grounding conductors.
“The employer shall use either ground fault circuit interrupters as specified in paragraph (b)(1)(ii) of this section or an assured equipment grounding conductor program as specified in paragraph (b)(1)(iii) of this section to protect employees on construction sites. These requirements are in addition to any other requirements for equipment grounding conductors.”
GFCI option: all 120-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites that are not part of the permanent wiring of the building or structure and that are in use by employees must have approved GFCIs for personnel protection.
“All 120-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites, which are not a part of the permanent wiring of the building or structure and which are in use by employees, shall have approved ground-fault circuit interrupters for personnel protection.”
Exception: receptacles on a two-wire, single-phase portable or vehicle-mounted generator rated not more than 5kW need no GFCI if the generator's circuit conductors are insulated from the generator frame and all other grounded surfaces.
“Receptacles on a two-wire, single-phase portable or vehicle-mounted generator rated not more than 5kW, where the circuit conductors of the generator are insulated from the generator frame and all other grounded surfaces, need not be protected with ground-fault circuit interrupters.”
A GFCI is a device for protecting personnel that de-energizes a circuit, or part of it, within an established time when current to ground exceeds a set value that is less than what would operate the circuit's overcurrent device.
“Ground-fault circuit interrupter. A device for the protection of personnel that functions to deenergize a circuit or portion thereof within an established period of time when a current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit.”
Assured program option: the employer must establish and implement the program on construction sites, covering all cord sets, receptacles that are not part of the building or structure, and cord-and-plug connected equipment that is available for use or used by employees.
“The employer shall establish and implement an assured equipment grounding conductor program on construction sites covering all cord sets, receptacles which are not a part of the building or structure, and equipment connected by cord and plug which are available for use or used by employees.”
A written description of the program, including the employer's specific procedures, must be available at the jobsite for inspection and copying by the Assistant Secretary and any affected employee.
“A written description of the program, including the specific procedures adopted by the employer, shall be available at the jobsite for inspection and copying by the Assistant Secretary and any affected employee.”
The employer must designate one or more competent persons (as defined in 1926.32(f)) to implement the assured program.
“The employer shall designate one or more competent persons (as defined in § 1926.32(f)) to implement the program.”
Under the program, each cord set, attachment cap, plug and receptacle of cord sets, and any cord-and-plug connected equipment must be visually inspected before each day's use for external defects (such as deformed or missing pins or insulation damage) and for signs of possible internal damage, except cord sets and receptacles that are fixed and not exposed to damage. Damaged or defective equipment may not be used until repaired.
“Each cord set, attachment cap, plug and receptacle of cord sets, and any equipment connected by cord and plug, except cord sets and receptacles which are fixed and not exposed to damage, shall be visually inspected before each day's use for external defects, such as deformed or missing pins or insulation damage, and for indications of possible internal damage. Equipment found damaged or defective shall not be used until repaired.”
Two tests are required on all cord sets, receptacles that are not part of the permanent wiring of the building or structure, and cord-and-plug connected equipment required to be grounded: all equipment grounding conductors must be tested for continuity, and each receptacle and attachment cap or plug must be tested for correct attachment of the equipment grounding conductor.
“The following tests shall be performed on all cord sets, receptacles which are not a part of the permanent wiring of the building or structure, and cord- and plug-connected equipment required to be grounded: (1) All equipment grounding conductors shall be tested for continuity and shall be electrically continuous. (2) Each receptacle and attachment cap or plug shall be tested for correct attachment of the equipment grounding conductor.”
The tests must be done before first use, before equipment returns to service after any repairs, before use after any incident reasonably suspected to have caused damage (such as a cord set being run over), and at intervals of no more than 3 months; cord sets and receptacles that are fixed and not exposed to damage are tested at intervals of no more than 6 months.
“All required tests shall be performed: (1) Before first use; (2) Before equipment is returned to service following any repairs; (3) Before equipment is used after any incident which can be reasonably suspected to have caused damage (for example, when a cord set is run over); and (4) At intervals not to exceed 3 months, except that cord sets and receptacles which are fixed and not exposed to damage shall be tested at intervals not exceeding 6 months.”
Tests must be recorded. The record must identify each receptacle, cord set and cord-and-plug connected equipment that passed, and show the last date it was tested or the interval it was tested for.
“Tests performed as required in this paragraph shall be recorded. This test record shall identify each receptacle, cord set, and cord- and plug-connected equipment that passed the test and shall indicate the last date it was tested or the interval for which it was tested.”
The test record may be kept by logs, color coding or other effective means, and must be kept until replaced by a more current record.
“This record shall be kept by means of logs, color coding, or other effective means and shall be maintained until replaced by a more current record.”
Grounding and polarity
A grounding terminal or grounding-type device on a receptacle, cord connector or attachment plug may be used only for grounding.
“A grounding terminal or grounding-type device on a receptacle, cord connector, or attachment plug shall not be used for purposes other than grounding.”
No grounded conductor may be attached to any terminal or lead so as to reverse the designated polarity.
“No grounded conductor shall be attached to any terminal or lead so as to reverse designated polarity.”
Under the exemption in 1926.404(f)(7)(iv)(C)(6) to the grounding rule for cord-and-plug connected equipment, listed or labeled portable tools and appliances protected by a system of double insulation, or its equivalent, need not be grounded, but they must be distinctively marked as double insulated.
“Listed or labeled portable tools and appliances protected by a system of double insulation, or its equivalent, need not be grounded. If such a system is employed, the equipment shall be distinctively marked to indicate that the tool or appliance utilizes a system of double insulation.”
Not covered here
We do not cover system grounding design (which AC and DC systems must be grounded, grounding electrode connections, made electrodes or high-voltage grounding), because they are installation design details beyond this guide's focus. We only write what an official source states, so study these parts with your certifying program's materials.
Temporary wiring
Temporary wiring must be removed immediately when construction, or the purpose the wiring was installed for, is complete.
“Temporary wiring shall be removed immediately upon completion of construction or the purpose for which the wiring was installed.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
For temporary-wiring branch circuits, runs of open conductors must be placed where they will not be physically damaged and fastened at intervals of no more than 10 feet, and no branch-circuit conductors may be laid on the floor.
“Runs of open conductors shall be located where the conductors will not be subject to physical damage, and the conductors shall be fastened at intervals not exceeding 10 feet (3.05 m). No branch-circuit conductors shall be laid on the floor.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
In temporary wiring, all lamps for general illumination must be protected from accidental contact or breakage, and metal-case sockets must be grounded. Temporary lights may not be hung by their electric cords unless the cords and lights are designed for that.
“All lamps for general illumination shall be protected from accidental contact or breakage. Metal-case sockets shall be grounded. (F) Temporary lights shall not be suspended by their electric cords unless cords and lights are designed for this means of suspension.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
Portable lighting used in wet or other conductive locations, such as drums, tanks and vessels, must run at 12 volts or less, but 120-volt lights may be used if they are protected by a GFCI.
“Portable electric lighting used in wet and/or other conductive locations, as for example, drums, tanks, and vessels, shall be operated at 12 volts or less. However, 120-volt lights may be used if protected by a ground-fault circuit interrupter.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
Extension cord sets used with portable electric tools and appliances must be three-wire type and designed for hard or extra-hard usage.
“Extension cord sets used with portable electric tools and appliances shall be of three-wire type and shall be designed for hard or extra-hard usage.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
Flexible cords and cables
Flexible cords and cables must be protected from damage and sharp corners and projections avoided. They may pass through doorways or other pinch points only if protection is provided to avoid damage.
“Flexible cords and cables shall be protected from damage. Sharp corners and projections shall be avoided. Flexible cords and cables may pass through doorways or other pinch points, if protection is provided to avoid damage.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
Unless needed for a use the rule permits, flexible cords and cables may not be used as a substitute for the fixed wiring of a structure, run through holes in walls, ceilings or floors, run through doorways, windows or similar openings (except as the temporary-wiring rule permits), attached to building surfaces, or concealed behind building walls, ceilings or floors.
“Unless necessary for a use permitted in paragraph (g)(1)(i) of this section, flexible cords and cables shall not be used: (A) As a substitute for the fixed wiring of a structure; (B) Where run through holes in walls, ceilings, or floors; (C) Where run through doorways, windows, or similar openings, except as permitted in paragraph (a)(2)(ii)(I) of this section; (D) Where attached to building surfaces; or (E) Where concealed behind building walls, ceilings, or floors.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
Flexible cords may be used only in continuous lengths without splice or tap. Hard service flexible cords No. 12 or larger may be repaired by a splice that keeps the insulation, outer sheath properties and usage characteristics of the cord.
“Flexible cords shall be used only in continuous lengths without splice or tap. Hard service flexible cords No. 12 or larger may be repaired if spliced so that the splice retains the insulation, outer sheath properties, and usage characteristics of the cord being spliced.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
Worn or frayed electric cords or cables may not be used.
“Worn or frayed electric cords or cables shall not be used.”
Extension cords may not be fastened with staples, hung from nails or suspended by wire.
“Extension cords shall not be fastened with staples, hung from nails, or suspended by wire.”
Safe work practices near circuits
No employer may let an employee work so close to any part of an electric power circuit that the employee could contact it in the course of work, unless the employee is protected against shock by de-energizing and grounding the circuit or by guarding it effectively by insulation or other means.
“No employer shall permit an employee to work in such proximity to any part of an electric power circuit that the employee could contact the electric power circuit in the course of work, unless the employee is protected against electric shock by deenergizing the circuit and grounding it or by guarding it effectively by insulation or other means.”
Where the exact location of underground electric powerlines is unknown, employees using jack-hammers, bars or other hand tools that may contact a line must be provided with insulated protective gloves.
“In work areas where the exact location of underground electric powerlines is unknown, employees using jack-hammers, bars, or other hand tools which may contact a line shall be provided with insulated protective gloves.”
Before work begins, the employer must find out, by inquiry, direct observation or instruments, whether any part of an energized electric power circuit, exposed or concealed, is located where the work could bring a person, tool or machine into physical or electrical contact with it.
“Before work is begun the employer shall ascertain by inquiry or direct observation, or by instruments, whether any part of an energized electric power circuit, exposed or concealed, is so located that the performance of the work may bring any person, tool, or machine into physical or electrical contact with the electric power circuit.”
Where such a circuit exists, the employer must post and maintain proper warning signs and tell employees where the lines are, the hazards involved and the protective measures to take.
“The employer shall post and maintain proper warning signs where such a circuit exists. The employer shall advise employees of the location of such lines, the hazards involved, and the protective measures to be taken.”
When fuses are installed or removed with one or both terminals energized, special tools insulated for the voltage must be used.
“When fuses are installed or removed with one or both terminals energized, special tools insulated for the voltage shall be used.”
Lockout and tagging of circuits
Controls that are to be deactivated during work on energized or de-energized equipment or circuits must be tagged.
“Controls that are to be deactivated during the course of work on energized or deenergized equipment or circuits shall be tagged.”
De-energized equipment or circuits must be rendered inoperative and have tags attached at all points where they can be energized.
“Equipment or circuits that are deenergized shall be rendered inoperative and shall have tags attached at all points where such equipment or circuits can be energized.”
Tags must be placed so they plainly identify the equipment or circuits being worked on.
“Tags shall be placed to identify plainly the equipment or circuits being worked on.”
Overhead clearances and wet locations
The outdoor conductor rules in 1926.404(c)(1) apply to branch circuit, feeder and service conductors rated 600 volts, nominal, or less and run outdoors as open conductors.
“Paragraphs (c)(1)(i) through (c)(1)(iv) of this section apply to branch circuit, feeder, and service conductors rated 600 volts, nominal, or less and run outdoors as open conductors.”
Such open conductors must have at least 10 feet of clearance above finished grade, sidewalks, or any platform or projection from which they might be reached, and 12 feet over areas with vehicle traffic other than truck traffic.
“Open conductors shall conform to the following minimum clearances: (A) 10 feet (3.05 m)—above finished grade, sidewalks, or from any platform or projection from which they might be reached. (B) 12 feet (3.66 m)—over areas subject to vehicular traffic other than truck traffic.”
They must have 15 feet of clearance over other areas with truck traffic, and 18 feet over public streets, alleys, roads and driveways.
“(C) 15 feet (4.57 m)—over areas other than those specified in paragraph (c)(1)(ii)(D) of this section that are subject to truck traffic. (D) 18 feet (5.49 m)—over public streets, alleys, roads, and driveways.”
Such conductors must be at least 3 feet from windows, doors, fire escapes or similar locations; conductors run above the top level of a window are considered out of reach from it.
“Conductors shall have a clearance of at least 3 feet (914 mm) from windows, doors, fire escapes, or similar locations. Conductors run above the top level of a window are considered to be out of reach from that window and, therefore, do not have to be 3 feet (914 mm) away.”
Switches, circuit breakers and switchboards installed in wet locations must be in weatherproof enclosures.
“Switches, circuit breakers, and switchboards installed in wet locations shall be enclosed in weatherproof enclosures.”
29 CFR 1926.405, Wiring methods, components, and equipment for general use
Definitions
In Subpart K, a qualified person is one familiar with the construction and operation of the equipment and the hazards involved.
“Qualified person. One familiar with the construction and operation of the equipment and the hazards involved.”
The Subpart K definitions of "approved" and "qualified person" apply in Subpart K instead of the general definitions in 1926.32.
“The definitions given here for "approved" and "qualified person" apply, instead of the definitions given in § 1926.32, to the use of these terms in subpart K.”
Exposed (as applied to live parts) means capable of being inadvertently touched or approached nearer than a safe distance by a person; it applies to parts not suitably guarded, isolated or insulated.
“Exposed. (As applied to live parts.) Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts not suitably guarded, isolated, or insulated.”
A wet location includes installations underground or in concrete slabs or masonry in direct contact with the earth, and locations subject to saturation with water or other liquids, such as places exposed to weather and unprotected.
“Wet location. Installations underground or in concrete slabs or masonry in direct contact with the earth, and locations subject to saturation with water or other liquids, such as locations exposed to weather and unprotected.”
Sources
- eCFR: 29 CFR 1926.402, Applicability (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1926.403, General requirements (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1926.449, Definitions applicable to this subpart (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1926.404, Wiring design and protection (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1926.405, Wiring methods, components, and equipment for general use (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1926.416, General requirements (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1926.417, Lockout and tagging of circuits (as of Nov 3, 2026)Checked November 5, 2026
Other OSHA Construction study guides: Introduction to OSHA, Fall protection, Scaffolds, Stairways and ladders, Excavations, Personal protective equipment, Health hazards, Hazard communication, Respirable crystalline silica, Welding and cutting, General safety and health