Question 2 of 7: Hazard-Control Priorities, Safety Devices, and Accident Investigation

Question 2: Hazard-Control Priorities, Safety Devices, and Accident Investigation (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) Principles and Priorities of Hazard Control (Hierarchy)

1. Elimination — remove the hazard entirely (most effective).
2. Substitution — replace with something less hazardous.
3. Engineering controls — guarding, isolation, ventilation, interlocks (control at source).
4. Administrative controls — procedures, training, signage, job rotation.
5. PPE — last line of defence, protects only the wearer.

Principle: control the hazard at source and as close to elimination as practicable; higher levels are preferred because they do not depend on human behaviour.

(ii) Purpose and Examples of Safety Devices

• Purpose — to prevent contact with a hazard, stop the hazard, or warn of it, without relying solely on the worker; they act automatically to keep the machine or process safe.
• Examples: interlocks, presence-sensing devices (light curtains, safety mats), two-hand controls/trip devices, emergency stops, pressure-relief valves/rupture discs, limit switches, safety valves, guards, and gate/barrier devices; also warning devices (alarms, lights).

(iii) Accident-Investigation Steps and Tools

Steps:

1. Respond/secure the scene — aid the injured, make safe, preserve evidence.
2. Gather facts — physical evidence, photographs, measurements, records.
3. Interview witnesses promptly and separately (fact-finding, not fault-finding).
4. Analyze — reconstruct the sequence; find immediate and root causes.
5. Develop conclusions and corrective actions addressing root causes.
6. Report; implement; follow up to verify effectiveness.

Investigation tools/equipment: camera/video, measuring tape/laser, sketch/diagramming tools, sample containers and evidence bags, PPE, notebook/forms and checklists, tags/barrier tape to secure the scene, flashlight, and where relevant testing/measuring instruments (gas detector, multimeter) and possibly witness statements forms.