32 multiple-choice questions for the OSHA Electrical Safety (Subpart S) Practice Test. Pick an answer to see the rule behind it, quoted from the official source.
1. An electrician is reviewing the specifications for a Class II combustible liquid to determine if it qualifies as a 'Volatile flammable liquid' under OSHA definitions. The liquid has a vapor pressure of 35 psia at 38 °C (100 °F). Under what specific temperature condition does this liquid meet the definition?
Answer: When its temperature is above its flash point. The rule states that for a Class II combustible liquid with the specified vapor pressure, it is considered volatile only if its temperature is above its flash point.
29 CFR § 1926.449: “or a Class II combustible liquid having a vapor pressure not exceeding 40 psia (276 kPa) at 38 °C (100 °F) whose temperature is above its flash point.”
2. An electrician is installing a temporary lighting string outdoors for a construction site. To ensure the installation qualifies as 'Festoon lighting' under the definitions provided, what is the minimum distance required between the two suspension points?
Answer: More than 15 feet (4.57 m) apart. The definition requires the suspension points to be more than 15 feet apart to classify the string as festoon lighting.
29 CFR § 1926.449: “Festoon lighting. A string of outdoor lights suspended between two points more than 15 feet (4.57 m) apart.”
3. An electrician is installing temporary wiring for a construction site remodel. Which of the following is a mandatory requirement for the branch circuits supplying fixed equipment?
Answer: Each branch circuit supplying fixed equipment must contain a separate equipment grounding conductor if run as open conductors. The regulation requires a separate equipment grounding conductor for branch circuits supplying fixed equipment when run as open conductors, while prohibiting floor laying and bare earth returns.
29 CFR § 1910.305(a): “Each branch circuit that supplies receptacles or fixed equipment shall contain a separate equipment grounding conductor if run as open conductors.”
4. When working on or near exposed energized parts, who is permitted to work on electric circuit parts or equipment that have not been deenergized?
Answer: Only qualified persons. The rule strictly limits work on energized equipment to qualified persons who are capable of working safely and familiar with necessary precautions.
29 CFR § 1910.333(c): “Only qualified persons may work on electric circuit parts or equipment that have not been deenergized under the procedures of paragraph (b) of this section.”
5. An electrician is installing non-heat-producing equipment, such as a junction box, in a hazardous (classified) location. Under what condition is this equipment exempt from having a marked operating temperature or temperature range?
Answer: If it is of the non-heat-producing type. The regulation allows non-heat-producing equipment like junction boxes to omit temperature markings, whereas heat-producing equipment only qualifies if its max temperature is under 100°C.
29 CFR § 1926.407(b): “Equipment of the non-heat-producing type (such as junction boxes, conduit, and fitting) and equipment of the heat-producing type having a maximum temperature of not more than 100 degrees C (212 degrees F) need not have a marked operating temperature or temperature range.”
6. An industrial worker is inspecting a completed wiring installation to ensure it meets insulation integrity standards. Which condition must the installation be free from?
Answer: Short circuits and grounds other than those required or permitted by the subpart. The rule mandates freedom from short circuits and unauthorized grounds, allowing only those grounds specifically required or permitted by the regulations.
29 CFR § 1910.303(b): “Completed wiring installations shall be free from short circuits and from grounds other than those required or permitted by this subpart.”
7. A worker is evaluating a pool constructed in the ground that is capable of holding water at a depth of 50 inches. According to the definitions, how must this facility be classified for electrical safety purposes?
Answer: Permanently installed swimming, wading, and therapeutic pool. Since the pool is in the ground and holds water deeper than 42 inches (1.07 m), it falls under the definition for permanently installed swimming/wading pools, not decorative fountains which are primarily for aesthetic value.
29 CFR § 1910.399: “Permanently installed swimming, wading, and therapeutic pools. Pools that are constructed in the ground or partially in the ground, and all other capable of holding water in a depth greater than 1.07 m (42 in.).”
8. An electrician is installing a disconnecting switch for a circuit operating at over 600 volts, nominal. According to the definitions provided, what is the primary function of this mechanical switching device?
Answer: To isolate a circuit or equipment from a source of power. The rule defines a disconnecting (or isolating) switch specifically as a device used to isolate circuits or equipment from their power source.
29 CFR § 1926.449: “A mechanical switching device used for isolating a circuit or equipment from a source of power.”
9. An electrician is installing a disconnecting means for a ride operator's console where the area is accessible to unqualified persons. What is the required feature for the enclosure of the switch or circuit breaker?
Answer: It must be of the lockable type. The regulation requires the enclosure to be lockable when accessible to unqualified persons to prevent unauthorized operation.
29 CFR § 1910.306(k): “Where accessible to unqualified persons, the enclosure for the switch or circuit breaker shall be of the lockable type.”
10. An industrial worker is working near outdoor electric equipment. What is required to protect this equipment from accidental contact by unauthorized personnel or vehicular traffic?
Answer: The equipment must be installed in suitable enclosures and protected from accidental contact. The rule mandates that outdoor equipment be in suitable enclosures and specifically protected from unauthorized personnel and vehicular traffic.
29 CFR § 1910.303(g): “Outdoor electric equipment shall be installed in suitable enclosures and shall be protected from accidental contact by unauthorized personnel, or by vehicular traffic, or by accidental spillage or leakage from piping systems.”
11. When work is performed near or on equipment or circuits which are or may be energized, what is the primary objective of the safety-related work practices employed?
Answer: To prevent electric shock or other injuries resulting from either direct or indirect electrical contacts. The general rule states that the purpose of these practices is specifically to prevent shock or injury from direct or indirect contacts when working on or near energized equipment.
29 CFR § 1910.333(a): “Safety-related work practices shall be employed to prevent electric shock or other injuries resulting from either direct or indirect electrical contacts, when work is performed near or on equipment or circuits which are or may be energized.”
12. An electrician is working on equipment likely to require examination or maintenance while energized. What is the minimum required width of the working space in front of this electric equipment?
Answer: The width of the equipment or 762 mm (30 in.), whichever is greater. The standard mandates that the working space width must accommodate the larger of either the equipment's physical width or a 30-inch minimum.
29 CFR § 1910.303(g): “The width of working space in front of the electric equipment shall be the width of the equipment or 762 mm (30 in.), whichever is greater.”
13. An industrial worker is setting up a center pivot irrigation machine. Where must the main disconnecting means be located to comply with safety standards?
Answer: At the point of connection of electrical power to the machine or visible and not more than 15.2 m (50 ft) from the machine. The rule specifies two acceptable locations: directly at the power connection point or within a visible 50-foot radius.
29 CFR § 1910.306(i): “The main disconnecting means for a center pivot irrigation machine shall be located at the point of connection of electrical power to the machine or shall be visible and not more than 15.2 m (50 ft) from the machine.”
14. A technician is installing electrical equipment in an area with a low ceiling. What is the minimum headroom required for the working space about service equipment, switchboards, panelboards, or motor control centers?
Answer: 6 feet 3 inches (1.91 m). The rule specifies that the minimum headroom for these specific types of equipment is 6 feet 3 inches.
29 CFR § 1926.403(i): “The minimum headroom of working spaces about service equipment, switchboards, panelboards, or motor control centers shall be 6 feet 3 inches (1.91 m).”
15. An electrician is working on a multicar elevator installation where interconnections between controllers are necessary for system operation and remain energized from a source other than the one disconnected. What safety measure is required at the disconnecting means?
Answer: A warning sign worded as required for multiple disconnecting means shall be mounted on or next to it. For multicar installations with energized interconnections from other sources, a warning sign similar to the one for multiple disconnecting means is required at the disconnecting means.
29 CFR § 1910.306(c): “A warning sign worded as required in paragraph (c)(8) of this section shall be mounted on or next to the disconnecting means where interconnections between controllers are necessary for the operation of the system on multicar installations that remain energized from a source other than the one disconnected.”
16. An electrician is installing temporary wiring on a construction site and needs to run branch-circuit conductors. Which of the following is prohibited for these conductors?
Answer: Laying them on the floor. The rule forbids laying branch-circuit conductors on the floor, while allowing the other listed methods.
29 CFR § 1926.405(a): “No branch-circuit conductors shall be laid on the floor.”
17. An electrician is preparing to work on exposed deenergized parts. If the parts have not been locked out or tagged in accordance with the standard, how must the electrician treat them?
Answer: As energized parts. Any deenergized part that lacks proper lockout or tagging must be treated as if it is still energized to ensure safety.
29 CFR § 1910.333(b): “Conductors and parts of electric equipment that have been deenergized but have not been locked out or tagged in accordance with paragraph (b) of this section shall be treated as energized parts, and paragraph (c) of this section applies to work on or near them.”
18. An electrician is installing a new circuit in a facility. To ensure the circuit is properly protected, they must identify the 'Branch circuit' as defined by OSHA. Which of the following accurately describes the physical scope of a branch circuit?
Answer: The circuit conductors between the final overcurrent device protecting the circuit and the outlets. The definition limits the branch circuit to the conductors located after the final overcurrent device and before the outlets.
29 CFR § 1910.399: “Branch circuit. The circuit conductors between the final overcurrent device protecting the circuit and the outlets.”
19. A worker is inspecting electrical cords on a construction site before use. According to OSHA rules, which condition of a cord prohibits its use?
Answer: The cord is worn or frayed. The standard bans the use of cords that are worn or frayed, while other conditions like dust or length are not prohibited by this specific rule.
29 CFR § 1926.416(e): “Worn or frayed electric cords or cables shall not be used.”
20. A worker is evaluating a heating device that generates heat via induction or dielectric methods for use under § 1910.306(g). How is this equipment classified?
Answer: Heating equipment. The rule defines equipment using induction or dielectric methods for heating purposes specifically as 'Heating equipment' for the cited section.
29 CFR § 1910.399: “Heating equipment. For the purposes of § 1910.306(g), the term “heating equipment” includes any equipment used for heating purposes if heat is generated by induction or dielectric methods.”
21. When grounding masts and metal structures supporting antennas, what condition must the grounding conductor meet according to OSHA standards?
Answer: It must be permanently and effectively grounded without splice or connection in the grounding conductor. The regulation strictly prohibits splices or connections in the grounding conductor for antenna masts to ensure a permanent and effective ground.
29 CFR § 1910.308(e): “Masts and metal structures supporting antennas shall be permanently and effectively grounded without splice or connection in the grounding conductor.”
22. A technician is selecting protection techniques for electrical equipment in a Class I, Zone 0 hazardous location. Which of the following techniques is permitted for this specific zone?
Answer: Intrinsic safety. According to the rule, Intrinsic safety is the only listed technique among the options that is permitted for Zone 0 locations, whereas the others are restricted to Zone 1 or Zone 2.
29 CFR § 1910.307(g): “Intrinsic safety—This protection technique is permitted for equipment in the Class I, Zone 0 or Zone 1 locations for which it is approved.”
23. A construction worker is installing temporary wiring and needs to provide access to the working space about electric equipment. What are the minimum dimensions for at least one entrance?
Answer: 24 inches wide and 6 feet 6 inches high. The standard requires a single entrance of at least 24 inches in width and 6 feet 6 inches in height for access to the working space.
29 CFR § 1926.403(j): “At least one entrance not less than 24 inches (610 mm) wide and 6 feet 6 inches (1.98 m) high shall be provided to give access to the working space about electric equipment.”
24. When an electrician uses flexible nonmetallic tubing to separately enclose conductors in a dry location, what is the maximum length allowed for a continuous length of tubing?
Answer: 4.57 m (15.0 ft). The rule states that flexible nonmetallic tubing must be in continuous lengths not exceeding 4.57 meters (15.0 feet).
29 CFR § 1910.305(a): “The tubing shall be in continuous lengths not exceeding 4.57 m (15.0 ft) and secured to the surface by straps at intervals not exceeding 1.37 m (4.5 ft).”
25. A worker wants to use a flexible cord to connect a stationary piece of equipment to facilitate its frequent interchange. Under what condition is this use permitted?
Answer: The cord shall be equipped with an attachment plug and shall be energized from a receptacle outlet. For permitted uses like frequent interchange of stationary equipment, the cord must have an attachment plug and be plugged into a receptacle, not hardwired.
29 CFR § 1926.405(g): “If used as permitted in paragraphs (g)(1)(i)(C), (g)(1)(i)(F), or (g)(1)(i)(H) of this section, the flexible cord shall be equipped with an attachment plug and shall be energized from a receptacle outlet.”
26. An electrician is wiring a switchboard where the circuit breaker handles are operated vertically. To ensure compliance with OSHA standards, how must the handle positions be configured?
Answer: The up position of the handle shall be the closed (on) position. Vertical operation requires the handle to be up when the breaker is closed (on).
29 CFR § 1910.304(f): “Where circuit breaker handles on switchboards are operated vertically rather than horizontally or rotationally, the up position of the handle shall be the closed (on) position.”
27. When installing a Class 3 inherently limited power source for a signaling circuit, what is the maximum circuit voltage allowed by the regulation?
Answer: 100 volts AC or DC. For a Class 3 inherently limited power source, the maximum circuit voltage is stated as 100 volts AC or DC.
29 CFR § 1926.408(b): “The maximum circuit voltage is 150 volts AC or DC for a Class 2 inherently limited power source, and 100 volts AC or DC for a Class 3 inherently limited power source.”
28. An electrician is installing a circuit breaker intended to interrupt current at fault levels. To comply with OSHA requirements regarding interrupting ratings, what must the electrician verify about the equipment?
Answer: The interrupting rating is sufficient for the nominal circuit voltage and the current available at the line terminals. The regulation requires the interrupting rating to match the nominal voltage and the available fault current at the line terminals, not just normal operating current or conductor size.
29 CFR § 1910.303(b): “Equipment intended to interrupt current at fault levels shall have an interrupting rating sufficient for the nominal circuit voltage and the current that is available at the line terminals of the equipment.”
29. An electrician is installing a heavy industrial lighting fixture that weighs 10 pounds. According to OSHA construction standards, how must this fixture be supported?
Answer: It must be securely supported by means other than the screw shell of a lampholder. Because the fixture weighs more than 6 pounds, it cannot rely on the lampholder's screw shell for support and requires independent secure support.
29 CFR § 1926.405(j): “A fixture that weighs more than 6 pounds (2.72 kg) or exceeds 16 inches (406 mm) in any dimension shall not be supported by the screw shell of a lampholder.”
30. An electrician is installing a junction box outdoors that is accessible to unqualified employees. The box cover weighs 40 kg (88 lb). According to OSHA rules, how must the cover be secured?
Answer: It shall be locked, bolted, or screwed on. Since the cover weighs less than 45.4 kg (100 lb), the exception for heavy underground covers does not apply, so it must be locked, bolted, or screwed on.
29 CFR § 1910.303(h): “Except for underground box covers that weigh over 45.4 kg (100 lb), doors and covers of enclosures used solely as pull boxes, splice boxes, or junction boxes shall be locked, bolted, or screwed on.”
31. An electrician is operating a boom truck with its structure elevated near energized overhead lines at 50kV or below. What is the minimum clearance distance the operator must maintain between the equipment and the lines?
Answer: 10 ft. (305 cm). For voltages to ground 50kV or below, the standard clearance for elevated vehicle structures is 10 feet.
29 CFR § 1910.333(c): “Any vehicle or mechanical equipment capable of having parts of its structure elevated near energized overhead lines shall be operated so that a clearance of 10 ft. (305 cm) is maintained.”
32. An electrician is inspecting a storage area and finds a flammable liquid with a flash point of 35°C (95°F). According to the definitions provided, how is this liquid classified?
Answer: Volatile flammable liquid. The rule defines a volatile flammable liquid as one with a flash point below 38°C, which matches the 35°C flash point in the scenario.
29 CFR § 1926.449: “Volatile flammable liquid. A flammable liquid having a flash point below 38 degrees C (100 degrees F) or whose temperature is above its flash point, or a Class II combustible liquid having a vapor pressure not exceeding 40 psia (276 kPa) at 38 °C (100 °F) whose temperature is above its flash point.”