6.3 Hierarchy of Controls

6.3 Hierarchy of Controls

Quick Answer: Control measures are ranked Elimination → Substitution → Engineering → Administrative → PPE. Always prefer the highest reasonably practicable level. Choosing PPE first for a serious hazard is a classic wrong answer on supervisory exams.

The hierarchy of controls is how HEMP’s Control stage should be populated. After you Identify and Assess, you select measures that reduce risk in order of effectiveness and reliability. Higher levels remove or redesign the hazard; lower levels depend more on people doing the right thing every time.

The Hierarchy (Top to Bottom)

Think of a pyramid: wide effort at the top removes risk for everyone; the tip (PPE) only protects the wearer and fails if fit, supply, or compliance fails.

1. Elimination

Elimination asks: Can we avoid the hazard completely?

Examples:

• Use a drone or remote camera instead of sending a person onto a fragile roof
• Prefabricate modules at ground level instead of extensive hot work at height
• Remove a redundant chemical from the process so it is no longer stored on site
• Schedule work in a vessel only after it is cleaned and declared gas-free—or avoid entry with remote cleaning tools

If elimination is reasonably practicable, do it. Supervisors often fail here by accepting “traditional methods” without asking whether the hazardous step is still necessary.

2. Substitution

Substitution keeps the function but reduces intrinsic danger.

Examples:

• Water-based paint instead of high-VOC solvent paint where specification allows
• Lower-voltage tools or battery systems instead of certain mains exposures (context-dependent)
• Less toxic cleaning agent instead of a highly corrosive product
• Mechanical lifting aids instead of two-person lifts of awkward loads (also overlaps ergonomics)

Substitution must be verified: the replacement should not introduce a worse hazard (for example, a “safer” chemical that is more flammable).

3. Engineering Controls

Engineering controls use hardware and design so protection does not depend solely on behaviour.

Examples:

• Machine guarding and interlocks
• Local exhaust ventilation for welding fumes
• Bunds and drip trays for chemical storage
• Fixed fall-prevention guardrails and platforms instead of relying only on harnesses
• Noise enclosures, light curtains, pressure relief, gas detection hardwired to alarms/ESD
• Physical segregation of vehicles and pedestrians on a busy Nigerian construction or plant site

Engineering controls need maintenance. A broken interlock or clogged scrubber is a paper control only.

4. Administrative Controls

Administrative controls manage people, timing, and rules:

• Permit-to-work, isolations, and simultaneous operations planning
• Safe work procedures and method statements
• Competence assurance, toolbox talks, and supervision ratios
• Job rotation to limit exposure time
• Speed limits, exclusion zones, and signage
• Journey management plans for driving risks

These are essential, but they fail when rushed, when contractors are uninformed, or when production pressure normalizes shortcuts. Never treat a procedure as equal to a locked isolation valve.

5. PPE (Last Line)

PPE includes hard hats, safety glasses, gloves, hearing protection, respirators, flame-resistant clothing, harnesses (as personal fall arrest), and safety footwear.

PPE is vital, but it is not the preferred primary control because:

• It protects only the wearer
• It requires correct selection, fit, training, and discipline
• It can fail (tear, wrong cartridge, poor seal)
• It does not remove the hazard from the workplace

Harnesses illustrate nuance: a travel-restraint system that prevents reaching an edge is stronger than fall-arrest after a fall begins; both are weaker than eliminating work at height or installing guardrails (engineering).

Applying the Hierarchy to Nigerian Supervisory Scenarios

Scenario A — Welding fumes in a workshop

1. Elimination: outsource or redesign joint to reduce welding? (sometimes)
2. Substitution: process change (e.g., different joining method) if feasible
3. Engineering: local exhaust ventilation / booths
4. Administrative: job rotation, hot-work rules, training
5. PPE: suitable respirator and eye protection as remaining layer

Wrong answer pattern: “Provide dust masks and continue” with no ventilation discussion.

Scenario B — Chemical transfer of corrosive liquid

1. Elimination: remove unnecessary chemical from inventory
2. Substitution: less hazardous product meeting process need
3. Engineering: closed transfer, pumps, bunding, eyewash/shower placement as facility design
4. Administrative: SDS, PTW/spill procedure, trained operators only
5. PPE: chemical gloves, face shield, apron—after higher controls

Scenario C — Pedestrian vs forklift conflict in a warehouse

1. Elimination: relocate storage to remove pedestrian crossing through vehicle lanes
2. Substitution: change layout/flow (one-way system)
3. Engineering: barriers, convex mirrors, segregated walkways, speed-limiting tech
4. Administrative: banksman rules, pedestrian zones, training
5. PPE: high-visibility clothing (helpful, not sufficient alone)

Scenario D — Noise from generators on a construction site

Prefer quieter equipment or enclosures (substitution/engineering) and exposure-time limits (administrative) before relying only on earplugs (PPE).

Layering Controls (Defence in Depth)

Real jobs use several layers. A confined-space entry may combine elimination of unnecessary entry, engineering ventilation and detection, administrative PTW and standby person, and PPE as appropriate. Layers should be independent where possible so one failure does not collapse the whole system.

Common Exam Traps

Supervisor Behaviours That Pass Audits

• Ask “can we eliminate or substitute?” in planning meetings
• Reject method statements that jump straight to PPE for high risks
• Verify engineering devices work (test gas detectors, check guards)
• Keep administrative controls alive (briefings, PTW discipline)
• Issue and enforce PPE as the final layer, not the strategy

Linking Back to Risk Matrices and ALARP

Moving up the hierarchy usually produces a larger drop in residual risk than adding another glove type. ALARP documentation should show you considered higher controls and either implemented them or recorded why they were not reasonably practicable. “PPE issued” without that consideration is weak evidence.

Practice Drill

For any task on your site, write five lines—one per hierarchy level—even if some lines say “not practicable because…”. That habit trains the exam reflex: PPE last, elimination first, with engineering preferred over rules-alone whenever the hazard is serious.

Master the hierarchy and you will correctly answer scenario questions that tempt you toward quick PPE solutions. Level 3 supervisors are expected to push risk reduction up the pyramid, not decorate workers with equipment while the hazard remains untouched.