NEBOSH CC Electrical Hazards on Site 3 — Questions and Answers
Question 1: What is the most common cause of electric shock on construction sites?
- Contact with damaged or poorly maintained electrical equipment (Correct answer)
- Overvoltage from the mains supply
- Lightning strikes
- Equipment overloading
Correct answer: Contact with damaged or poorly maintained electrical equipment
The most common cause of electric shock on construction sites is contact with damaged or poorly maintained electrical equipment, including damaged cables, faulty tools and inadequate insulation. Regular inspection and maintenance are critical.
Question 2: What is an 'arc flash' hazard in electrical safety?
- An intense release of heat and light energy caused by an electrical arc between conductors (Correct answer)
- A gradual overheating of electrical cables
- Sparks from grinding operations near cables
- The light emitted by fluorescent lighting tubes
Correct answer: An intense release of heat and light energy caused by an electrical arc between conductors
An arc flash is an extremely dangerous event involving an intense burst of heat (reaching thousands of degrees), light and pressure caused by an electrical arc between conductors. It can cause severe burns, fire and blast injuries.
Question 3: Why must combustion engines not be used in enclosed spaces on construction sites?
- They produce carbon monoxide, which is a colourless, odourless toxic gas (Correct answer)
- They are too noisy for enclosed spaces
- They emit excessive heat
- They consume excessive amounts of fuel
Correct answer: They produce carbon monoxide, which is a colourless, odourless toxic gas
Combustion engines (including petrol and diesel generators) produce carbon monoxide as a combustion byproduct. Carbon monoxide is colourless, odourless and highly toxic — it can build up in enclosed spaces and cause rapid unconsciousness and death.
Question 4: What is the recommended frequency for formal inspection of electrical equipment used on a construction site?
- Before first use and at regular intervals based on the type and use of equipment (Correct answer)
- Only when a fault is suspected
- Once per year regardless of use
- Monthly for all equipment
Correct answer: Before first use and at regular intervals based on the type and use of equipment
The frequency of electrical equipment inspection should be based on the type of equipment, how often it is used and the conditions of use. On construction sites, equipment may need inspection before each use due to harsh conditions.
Question 5: What is a 'permit to work' system used for in electrical work?
- To formally control and authorise electrical work, ensuring isolation and safe conditions before work begins (Correct answer)
- To record the names of all workers on the electrical installation
- To document the electrical layout of the building
- To log all electrical faults found during inspection
Correct answer: To formally control and authorise electrical work, ensuring isolation and safe conditions before work begins
A permit to work for electrical work formally controls who can work on electrical systems, ensures proper isolation has been carried out, specifies the work to be done and authorises only competent persons to proceed. It prevents accidental re-energisation.
Question 6: What action should be taken if an electric shock casualty is found in contact with a live supply?
- Isolate the power supply before touching the casualty (Correct answer)
- Pull the casualty away immediately using your hands
- Throw water over the casualty
- Administer CPR immediately without isolating the supply
Correct answer: Isolate the power supply before touching the casualty
If a casualty is in contact with a live supply, the rescuer must isolate the power before making any physical contact. Touching a casualty connected to a live supply will result in the rescuer also receiving an electric shock.
NEBOSH CC Electrical Hazards on Site 3
What is the most common cause of electric shock on construction sites?