Question 2 of 7: Hazard Control Programs, Selecting a Control Method for Chemical Agents, and the Main Ways to Control a Hazard

Question 2: Hazard Control Programs, Selecting a Control Method for Chemical Agents, and the Main Ways to Control a Hazard (20 marks: 6/7/7)

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) Hazard Control Programs (CCOHS) and the Need for Regular Monitoring and Review

The Canadian Centre for Occupational Health and Safety (CCOHS) defines a hazard control program as the organized, documented set of activities an employer uses to identify hazards, select and implement appropriate controls, and confirm those controls remain effective — it is the operational program that carries out the commitment made in the policy statement (Question 1). CCOHS's model treats it as a continuous cycle, not a one-time project:

• Hazard identification and assessment — systematic inspections, job/task analysis, and incident/near-miss data are used to identify hazards and rank them by risk (severity × likelihood).
• Control selection — controls are chosen following the hierarchy of controls (elimination through PPE, described in part (iii)), documented, and assigned an owner and a target date.
• Implementation — the selected controls are installed/put into effect, with the workers affected trained on the new or changed procedure.
• Monitoring and evaluation — the program tracks whether each control is actually in place and functioning (not just installed once and forgotten) and whether exposure/incident metrics have actually improved.

Regular monitoring and review is important because a control's effectiveness is not static:

• Processes, equipment, and materials change — a new chemical, a faster line speed, or a modified process can silently invalidate a control that was adequate when it was first selected.
• Controls degrade physically — guards get removed for maintenance and not replaced, ventilation filters load up and lose capacity, interlocks get bypassed for convenience — none of which shows up unless someone actively checks.
• Regulatory and standard limits change — an exposure limit or code requirement can tighten over time, and a control adequate under an old limit may no longer be compliant.
• New hazard knowledge emerges — a substance's toxicological profile or an equipment failure mode can become better understood after a control was first put in place, warranting reassessment.
• Continuous improvement / due diligence — a documented, periodic review is itself evidence, in the event of an incident or inspection, that the employer exercised the diligence the Act requires, rather than installing a control once and never revisiting it.

(ii) Determining the Control Method Required for a Chemical Agent

The control method for a chemical agent is not chosen in the abstract; it follows directly from a structured assessment of the agent and the exposure situation:

• Identify the agent and its properties — consult the safety data sheet (SDS) for toxicity (target organs, acute vs. chronic effects), physical form (gas, vapour, mist, dust, fume), volatility/vapour pressure, flammability, and reactivity, since the physical form alone determines whether respiratory, dermal, or both routes of entry are relevant.
• Determine the route(s) of exposure — inhalation, skin/eye contact, or ingestion — a volatile solvent is primarily an inhalation hazard and needs ventilation-based control, whereas a corrosive liquid handled by hand is primarily a dermal-contact hazard and needs containment/PPE at the point of contact.
• Quantify exposure against the applicable occupational exposure limit (e.g., the ACGIH TLV or the provincial OEL) via air sampling or, where sampling isn't yet available, an exposure-modelling estimate — the gap between measured/estimated exposure and the limit indicates how aggressive the control needs to be.
• Assess the task and quantity involved — a small, infrequent bench-scale use of a chemical warrants a different control (e.g., local ventilation, PPE) than continuous, large-volume use in a production process (which may require engineered containment or process substitution).
• Apply the hierarchy of controls to the identified route/quantity/exposure gap, starting from elimination/substitution and moving down only as far as necessary (detailed in part (iii)) — the required "level" of control is the highest tier in the hierarchy that is technically and economically feasible for the actual exposure identified, not a default choice of PPE.
• Verify by post-control monitoring — air sampling or biological monitoring after the control is implemented confirms exposure is actually brought under the limit, closing the loop back to part (i)'s "monitor and review."

(iii) The Main Ways to Control a Hazard (Hierarchy of Controls)

Hazard controls are ranked, from most to least effective, in the internationally recognized hierarchy of controls (embodied in CSA Z1002):

• Elimination — physically remove the hazard entirely (e.g., stop using a hazardous chemical, remove a pinch point from a redesigned machine). The most effective control because, once eliminated, the hazard cannot cause harm regardless of human behaviour.
• Substitution — replace the hazard with a less hazardous alternative (e.g., a water-based solvent for a flammable/toxic organic solvent, a lower-voltage circuit for a higher one). Nearly as effective as elimination, but the residual hazard is smaller rather than absent.
• Engineering controls — physically isolate people from the hazard or the hazard from people, without relying on any human action once installed (machine guards, local exhaust ventilation, noise enclosures, interlocks). Effective because they function independent of behaviour, but require capital investment and maintenance to stay effective.
• Administrative controls — change the way people work: procedures, training, job rotation to limit exposure duration, signage, permit-to-work systems, scheduling hazardous work when fewer workers are present. Less reliable than engineering controls because they depend on consistent human compliance.
• Personal protective equipment (PPE) — respirators, gloves, hearing protection, eye protection worn by the individual worker. The last line of defence: it protects only the wearer, only while worn and properly fitted/maintained, and does nothing to reduce the hazard itself — used where higher-tier controls cannot fully eliminate the residual risk.

In practice, several tiers are combined (e.g., engineering ventilation plus an administrative permit system plus PPE as backup) rather than relying on a single tier alone, and the selection always starts from the top of the hierarchy and works down only as far as the residual risk requires.