STSC Electrical Safety in Construction 5 — Questions and Answers
Question 1: What does the 'one-hand rule' recommend when workers must work near energized electrical panels?
- Keep one hand in a pocket or behind your back to prevent current from crossing the chest (Correct answer)
- Always use one hand to hold a non-conductive tool
- Touch only one conductor at a time
- Use one hand to brace against a grounded surface
Correct answer: Keep one hand in a pocket or behind your back to prevent current from crossing the chest
The one-hand rule reduces the chance of current passing through the heart by keeping one hand away from any grounded surface when working near energized parts.
Question 2: Under OSHA 1926.405, what is the maximum length of flexible cord that may be used as a substitute for permanent wiring on a construction project?
- Flexible cord may never be used as a substitute for permanent wiring (Correct answer)
- Up to 25 feet
- Up to 50 feet
- Up to 100 feet if protected by GFCI
Correct answer: Flexible cord may never be used as a substitute for permanent wiring
OSHA prohibits using flexible cord or extension cords as a substitute for the fixed wiring of a structure under any length restriction.
Question 3: Which instrument should a qualified electrician use to verify that a circuit is de-energized before beginning work under LOTO?
- A clamp-on ammeter
- A non-contact voltage tester or voltmeter rated for the circuit voltage (Correct answer)
- An ohmmeter set to resistance mode
- A continuity tester with an internal battery
Correct answer: A non-contact voltage tester or voltmeter rated for the circuit voltage
A non-contact voltage tester or voltmeter rated for the expected voltage confirms de-energization; ohm and continuity testers cannot safely detect live voltage.
Question 4: A construction crew is working inside a steel structure during a thunderstorm. Lightning strikes a nearby tower and induces a surge on the site's temporary power system. Which protective device is specifically designed to limit damage from this type of transient overvoltage?
- Ground fault circuit interrupter (GFCI)
- Arc fault circuit interrupter (AFCI)
- Surge protective device (SPD) (Correct answer)
- Thermal overload relay
Correct answer: Surge protective device (SPD)
Surge protective devices (SPDs) clamp transient overvoltages caused by lightning or switching surges, protecting equipment and wiring from insulation breakdown.
Question 5: What condition classifies a work location as a 'wet location' for purposes of electrical equipment selection on a construction site?
- Relative humidity above 60%
- Any outdoor location regardless of current weather
- A location subject to saturation with water or other liquids (Correct answer)
- Any location within 10 feet of plumbing fixtures
Correct answer: A location subject to saturation with water or other liquids
OSHA and the NEC define a wet location as one exposed to weather or subject to saturation by water, which requires equipment rated for wet location use.
Question 6: Which of the following is NOT an acceptable method to protect workers from overhead power line contact when using a crane on a construction site?
- De-energizing and grounding the lines
- Installing insulating line guards approved by the utility
- Maintaining the required minimum approach distance
- Posting a spotter to watch only the load swing (Correct answer)
Correct answer: Posting a spotter to watch only the load swing
A spotter alone watching only the load is insufficient; OSHA requires the spotter to observe clearance from power lines specifically and have authority to stop operations.
Question 7: An employee receives an electric shock and is in contact with an energized conductor. What is the supervisor's correct first action?
- Grab the employee's arm and pull them away from the conductor
- De-energize the circuit or use a non-conductive object to separate the victim from the source (Correct answer)
- Call 911 and wait for emergency services before taking any action
- Pour water on the conductor to cool it before touching the victim
Correct answer: De-energize the circuit or use a non-conductive object to separate the victim from the source
The rescuer must first break contact without touching the victim directly — by cutting power or using a non-conductive object — to avoid becoming a second victim.
STSC Electrical Safety in Construction 5
What does the 'one-hand rule' recommend when workers must work near energized electrical panels?