In this module
Objectives covered: LO 2.6.1. By the end you will be able to:
- Apply the five levels of the hierarchy of controls to real hazards.
- Explain why higher-level controls are more reliable than lower-level ones.
- Combine controls so no single failure leads to harm.
6.1 The five levels
| Level | Idea | Example: noisy compressor room |
|---|---|---|
| 1. Elimination | Remove the hazard | Move the compressor outside the work building |
| 2. Substitution | Use something less hazardous | Buy a low-noise screw compressor instead of a reciprocating one |
| 3. Engineering | Isolate people from the hazard | Acoustic enclosure, silencers, anti-vibration mounts |
| 4. Administrative | Change how people work | Signs, limited entry time, rotation, training |
| 5. PPE | Protect the person | Earmuffs or earplugs when entering |
6.2 Why the order matters
Controls at the top work without needing people to do the right thing every time. Controls at the bottom depend on people remembering, choosing and complying, every day, on every shift. A machine guard works at 3 a.m. when the operator is tired; a sign may not be read.
6.3 Layers of protection
Each control has holes, like slices of Swiss cheese. An accident happens when the holes line up. Using several layers together means one failure does not lead to harm.
The Tazreen Fashions fire in November 2012 killed more than 100 workers. Exits were locked and there were no fire-rated stairs. Since then, Accord and RSC inspections have pushed layered controls: fire-rated doors and separated stairs (engineering), sprinklers and fire alarms (engineering), no storage on stairs and regular drills (administrative). No single layer is enough; together they save lives.
6.4 Common controls by hazard
- Machinery: fixed guards, interlocked guards, light curtains, two-hand controls, emergency stops.
- Chemicals: closed transfer, local exhaust ventilation, secondary containment, labelling, SDS, PPE.
- Electrical: RCDs / ELCBs, earthing, enclosures, lockout, qualified electricians only.
- Work at height: do the work on the ground, guardrails, scaffolds, nets, then harnesses.
- Manual handling: trolleys, hoists, smaller loads, adjustable work heights.
- NIOSH hierarchy of controls; ISO 45001 clause 8.1.2; ILO-OSH 2001 guidelines.
- OSHA 1910.212: general machine guarding. ISO 12100: risk reduction for machinery design.
Learning Check
Answer these two questions to check your understanding. You can try again as many times as you like.