Fire, Signs & Electrical Safety

Under the Regulatory Reform (Fire Safety) Order 2005, who is normally the 'responsible person' for fire safety on a construction site?

• AThe designer who produced the drawings
• BThe fire and rescue authority for the area
• CThe client's insurer underwriting the works
• DThe principal contractor in control of the site✓

Answer: The Fire Safety Order places its duties on the person in control of the premises, which on a construction site is normally the principal contractor. On a construction site the HSE enforces the Order (the fire and rescue authority enforces it in occupied premises) rather than owning the duty, and neither the designer nor the insurer controls the site day to day.

Under the Fire Safety Order, when must the responsible person for a construction site record the fire risk assessment in writing?

• AOnly where hot works or a timber frame raise the fire risk
• BOnly where the works are expected to last more than 30 days
• COnly once five or more people are employed on the site
• DIn every case, in full, whatever the size of the workforce✓

Answer: Since 1 October 2023, when section 156 of the Building Safety Act 2022 amended Article 9 of the Regulatory Reform (Fire Safety) Order 2005, every responsible person must record the fire risk assessment in full, including the prescribed information, regardless of how many people are employed. The old threshold of five or more employees no longer applies, and hot works, timber-frame construction and project duration affect the level of risk but were never the legal trigger for recording it.

Which extinguisher should be provided at the fire point next to the site's temporary electrical distribution unit?

• AAqueous film foam (cream band)
• BWet chemical (yellow band)
• CCarbon dioxide (black band)✓
• DWater additive (red band)

Answer: Carbon dioxide is non-conductive and leaves no residue, so it is the extinguisher for fires involving live electrical equipment. Water, foam and wet chemical media all conduct electricity and would put the user at risk of electrocution if discharged onto live apparatus.

An electrician is about to replace a damaged socket on a site distribution unit. What must be done before the work starts?

• AIsolate the supply, lock it off and prove the circuit dead✓
• BPost a warning sign on the unit and work on it with care
• CWear insulating gloves and work on the unit while it is live
• DSwitch the unit off at the RCD and start work straight away

Answer: The Electricity at Work Regulations require live working to be avoided wherever practicable, so the supply must be isolated, secured against reconnection with a lock and then proved dead with a tested voltage indicator. Tripping an RCD without locking off can be undone by anyone, and gloves or a sign do nothing to remove the danger of a live circuit.

Roofers finish using a gas torch on a flat roof at 15:30 under a hot-work permit. What should happen next?

• AThe roof is damped down with water and then left for the evening
• BA fire marshal signs off the permit as soon as the crew leaves
• CA fire watch continues for at least an hour after the torch is put down✓
• DThe permit is closed as soon as the torch and cylinders are stored

Answer: Smouldering can start well after hot work ends, so a fire watch of at least 60 minutes is a standard permit condition before the area is checked and the permit closed. Closing the permit or signing it off as soon as the crew leaves removes that check, and damping down followed by leaving the roof unattended gives a hidden fire time to develop.

Why must LPG cylinders on site be kept away from drains, gullies and excavations?

• ALeaking gas is lighter than air and rises out of low points
• BCylinders corrode rapidly where the ground is damp or wet
• CLeaking gas reacts with standing water to form an acid
• DLeaking gas is heavier than air and pools in low points✓

Answer: LPG vapour is denser than air, so a leak flows downhill and collects in drains, pits and trenches where it can reach an ignition source and explode. It does not form an acid with water, it sinks rather than rises, and damp corrosion is a storage-condition issue rather than the reason for keeping cylinders away from low points.

A sign on site shows a black pictogram inside a yellow triangle with a black border. What kind of sign is it?

• AProhibited activity
• BMandatory action
• CWarning of a hazard✓
• DSafe condition

Answer: Under the Safety Signs and Signals Regulations a yellow triangle with a black border and pictogram is the warning sign format, alerting people to a hazard such as overhead loads. Mandatory instructions use a blue circle, prohibitions a red circle with a diagonal bar, and safe-condition information a green rectangle.

What is the shape and colour of a mandatory safety sign, such as 'safety helmets must be worn'?

• ABlue circle with a white pictogram✓
• BYellow triangle with a black border
• CRed circle with a diagonal bar
• DGreen rectangle with a white pictogram

Answer: Mandatory signs that tell people what they must do are round with a blue background and a white symbol. A red circle with a diagonal bar prohibits an activity, a green rectangle shows a safe condition such as an escape route, and a yellow triangle warns of a hazard.

Which statement about safety signs on a construction site is correct?

• ASigns supplement other risk controls but do not replace them✓
• BSigns are required only where the public can access the site
• CSigns replace the need for a toolbox talk on the hazard shown
• DSigns are an adequate control on their own for low-risk hazards

Answer: The Safety Signs and Signals Regulations require signs where a risk remains after other controls, and a sign only warns or instructs; it removes nothing. Relying on a sign as the sole control, restricting signage to public-facing areas or treating a sign as a substitute for briefing the workforce all leave the underlying risk unmanaged.

What is the preferred supply for mains-powered portable tools on a UK construction site?

• A230 V single-phase protected by a 300 mA RCD
• B110 V centre-tapped to earth, so 55 V to earth✓
• C400 V three-phase with a 30 mA RCD at the board
• D12 V extra-low voltage from a step-down transformer

Answer: A 110 V centre-tapped transformer limits the voltage to earth to 55 V, which is unlikely to cause a fatal shock, and it is the industry standard for portable tools where battery power is not used. A 300 mA RCD offers no personal shock protection, three-phase 400 V is for fixed plant, and 12 V is impractical for power tools.

If 230 V equipment has to be used on site, what protection must be provided for the user?

• AA residual current device at 300 mA
• BA residual current device rated at 30 mA✓
• CA step-down transformer at each socket
• DA double-pole isolator at the site board

Answer: A 30 mA RCD disconnects the supply quickly enough to protect against a fatal shock, which is why it is the required protection whenever 230 V equipment is used on site. A 300 mA device is for fire protection, an isolator only allows the supply to be switched off, and a transformer at every outlet would convert the supply to 110 V rather than protect 230 V use.

An excavator boom touches a live overhead power line. What should the operator do?

• AClimb down at once and check the boom and tyres for burn damage
• BStep down carefully, keeping a hand on the machine to earth it
• CLower the boom, leave the cab and walk the line to find the fault
• DRemain in the cab and warn others to keep away from the machine✓

Answer: HSE guidance GS6 says the operator should stay in the cab, try to drive clear if possible, and keep others away until the network operator confirms the line is dead, because the machine and the ground around it may be live. Stepping down while touching the machine bridges the voltage across the body, and leaving the cab to inspect the boom or the line exposes the operator to step and touch potentials.

During safe digging, the team exposes a buried cable with a black sheath. What does the colour tell the site manager?

• AOnly an indication; every service is still treated as live✓
• BThe depth at which the service was laid by the utility
• CA guarantee of what the service carries, so it can be cut
• DThe ownership of the service, so the correct owner can be billed

Answer: HSG47 warns that the colours of buried services are indicative only, as older or private services may not follow the conventions, so every service must be assumed live and dangerous until its owner confirms otherwise. A colour never authorises cutting, does not identify the owner reliably and says nothing about depth.

Who may install the temporary electrical supply for a construction site?

• AThe site manager, once the risk assessment is signed
• BAny operative holding a current CSCS card
• CThe plant hire company delivering the generator
• DA competent electrician working to BS 7671✓

Answer: Temporary site installations must be designed, installed and tested to BS 7671 by a competent electrician, and the Electricity at Work Regulations restrict electrical work to those with the necessary knowledge and experience. A CSCS card, delivering a generator or signing a risk assessment does not make someone competent to install a supply.