Question 2 of 7: Hazard Sources, Control Priorities, and Warning Devices

Question 2: Hazard Sources, Control Priorities, and Warning Devices (20 marks: 7/6/7)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(i) Sources of Hazards in Industry

• Mechanical — moving parts, rotating shafts, nip points, cutting/pinch points, falling objects.
• Electrical — shock, arc flash, static, faulty wiring, overloads.
• Chemical — toxic, corrosive, flammable or reactive substances; dusts, mists, vapours.
• Physical/energy — noise, vibration, heat/cold, radiation (ionizing and non-ionizing), pressure.
• Fire and explosion — flammable materials, ignition sources, combustible dust.
• Ergonomic — manual handling, repetitive motion, poor posture, awkward workstations.
• Biological — bacteria, viruses, moulds (in relevant industries).
• Environmental/workplace — poor housekeeping, inadequate lighting, slippery or cluttered floors, working at height, confined spaces.
• Human/organizational — fatigue, inadequate training, poor supervision, weak procedures.

(ii) Priority Order for Hazard Controls (the Hierarchy of Controls)

1. Elimination — remove the hazard entirely (most effective).
2. Substitution — replace with a less hazardous material, process or equipment.
3. Engineering controls — isolate people from the hazard: guarding, enclosure, ventilation, interlocks.
4. Administrative controls — change how people work: procedures, training, job rotation, signage, scheduling.
5. Personal protective equipment (PPE) — last line of defence, protecting the individual (least reliable, as it depends on correct use).

The priority runs from controlling the hazard at source down to protecting the individual; higher levels are preferred because they do not rely on human behaviour.

(iii) Steps for the Effective Use of Warning Devices

• Use warnings only after higher-order controls have been applied—warnings supplement, never replace, elimination/engineering controls.
• Identify the specific hazard and the exact behaviour or response required.
• Select a device appropriate to the hazard and environment (visual, audible, or both; account for noise, lighting, distance).
• Make the signal clearly perceptible—loud/bright enough above background, and distinguishable from other signals.
• Make it understandable and standardized—consistent colours/symbols/sounds, plain language, recognized conventions.
• Give it in time to react, and ensure it prompts the correct action.
• Train workers to recognize and respond to each warning.
• Test, inspect and maintain devices regularly so they function when needed; avoid warning overload (too many signals dilute response).