NEBOSH CC Working at Height in Construction 2 — Questions and Answers
Question 1: What is the maximum recommended height for a free-standing mobile tower scaffold used outdoors?
- The height should not exceed a base-to-height ratio of 1:3 outdoors (or 1:3.5 indoors) (Correct answer)
- 10 metres regardless of base width
- Any height provided it has outriggers
- There is no height limit
Correct answer: The height should not exceed a base-to-height ratio of 1:3 outdoors (or 1:3.5 indoors)
For stability, mobile tower scaffolds should not exceed a base-to-height ratio of 1:3 outdoors and 1:3.5 indoors. PASMA guidance provides specific recommendations. Outriggers and stabilisers can increase the effective base dimension. The scaffold must never be moved with persons or loose materials on the platform.
Question 2: A construction worker falls 4 metres from a scaffold and is suspended in their safety harness. What is the main risk from prolonged suspension in a harness?
- Suspension trauma (orthostatic intolerance) which can be fatal within 30 minutes (Correct answer)
- Hypothermia only
- Sunburn
- Boredom
Correct answer: Suspension trauma (orthostatic intolerance) which can be fatal within 30 minutes
Suspension trauma (also called harness hang syndrome) occurs when blood pools in the legs during prolonged vertical suspension, reducing venous return and cardiac output. It can cause unconsciousness within minutes and death within 30 minutes. A rescue plan must be in place before any work at height involving harnesses.
Question 3: Under the Work at Height Regulations 2005, what must be in place before any work at height is carried out?
- A suitable and sufficient risk assessment with a rescue plan for foreseeable emergencies (Correct answer)
- Only a verbal instruction from the site manager
- Written permission from the HSE
- A medical certificate for each worker
Correct answer: A suitable and sufficient risk assessment with a rescue plan for foreseeable emergencies
Regulation 4 requires proper planning, including risk assessment, selection of appropriate work equipment, and emergency rescue procedures. No work at height should commence without considering how a fallen or stranded worker would be rescued promptly to prevent suspension trauma.
Question 4: What is the primary advantage of using safety nets as collective fall protection compared to personal fall arrest systems?
- They protect all workers in the area passively without requiring individual training, fitting, or action (Correct answer)
- They are cheaper than harnesses
- They are easier to install
- They can be reused indefinitely without inspection
Correct answer: They protect all workers in the area passively without requiring individual training, fitting, or action
Safety nets provide passive collective protection — they protect everyone in the work area without requiring individual action, training in use, or correct fitting. This makes them more reliable than personal fall arrest systems which depend on each worker correctly wearing and attaching their equipment.
Question 5: A worker needs to use a ladder to access a scaffold platform 5 metres above ground. What angle should the ladder be set at?
- 75 degrees (1 out for every 4 up) (Correct answer)
- 45 degrees
- 90 degrees (vertical)
- 60 degrees
Correct answer: 75 degrees (1 out for every 4 up)
Ladders should be placed at an angle of 75 degrees to the horizontal, which equates to a ratio of 1 unit out for every 4 units up (the 1:4 rule or 4-to-1 rule). The ladder must extend at least 1 metre above the landing point, be secured to prevent slipping, and rest on a firm, level surface.
Question 6: When is it acceptable to use a ladder as a work platform on a construction site?
- Only for light work of short duration (up to 30 minutes) where the risk assessment shows a ladder is the most appropriate equipment (Correct answer)
- For any task regardless of duration
- Never — ladders are only for access
- Only when scaffolding is not available from the supplier
Correct answer: Only for light work of short duration (up to 30 minutes) where the risk assessment shows a ladder is the most appropriate equipment
Ladders may be used as a work platform only where a risk assessment shows the task is low-risk, short duration (generally up to 30 minutes), requires only light work (one hand can maintain three points of contact), and no better alternative is reasonably practicable. They remain primarily access equipment.
NEBOSH CC Working at Height in Construction 2
What is the maximum recommended height for a free-standing mobile tower scaffold used outdoors?