Question 4 of 7: Hazardous-Material Controls and Confined Spaces

Question 4: Hazardous-Material Controls and Confined Spaces (20 marks: 7/7/6)

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) Controls for Hazardous-Material Exposure

• Elimination/substitution — remove the hazardous material or replace with a safer one.
• Engineering controls — enclosure/isolation of the process; ventilation (local exhaust at source; general dilution); wet methods to suppress dust.
• Administrative controls — safe work procedures, limiting exposure time, hygiene practices (washing, no eating in work areas), labelling and SDS, training.
• PPE — respirators, gloves, chemical suits, eye protection (last line).
• Backed by exposure monitoring, medical surveillance, and emergency provisions (eyewash, showers, spill response).

(ii) Characteristics and Examples of Confined Spaces

• Characteristics: large enough to enter and work; limited/restricted means of entry or exit; not designed for continuous human occupancy; may accumulate a hazardous atmosphere.
• Examples: tanks, vessels, boilers, silos, hoppers, storage bins, sewers, pipelines, tunnels, pits, manholes, ductwork, and the interiors of large equipment.

(iii) Main Hazards of Confined Spaces

• Atmospheric — oxygen deficiency (displacement/consumption) or enrichment; toxic gases/vapours (H₂S, CO); flammable/explosive atmospheres.
• Engulfment — burial/drowning in liquids or free-flowing solids (grain, sand).
• Entrapment — converging walls or downward-sloping floors trapping the entrant.
• Physical/mechanical — moving parts, electrical, heat, noise, falls.
• Difficult rescue — restricted access makes rescue slow and dangerous (many fatalities are would-be rescuers). Hence permits, testing, ventilation, isolation and an attendant/rescue plan are essential.