Hierarchy of Controls and Control Selection
Hierarchy of Controls and Control Selection
This domain tests control selection logic: why elimination and substitution rank above engineering controls, why administrative controls and PPE rank lower, and how to choose a feasible combination for each hazard.
Core rules
- The NIOSH hierarchy is elimination, substitution, engineering controls, administrative controls, and PPE. Effectiveness generally decreases down the list; PPE is last because it depends on fit, use, and maintenance.
- Apply the hierarchy to every hazard and task, not once per facility. A control that works for vapor may not control dust or noise.
- Substitution must be safer. Replacing a toxic solvent with a flammable one trades poisoning for fire risk; replacing silica abrasive with a less hazardous blasting media can be a valid substitution.
- Engineering controls isolate people from the hazard at the source: enclosure, local exhaust, guarding, sound enclosures, and automation.
- Administrative controls change how work is done: rotation, permits, procedures, training, housekeeping, and access control. They do not remove the hazard.
- Select controls on effectiveness, reliability, worker acceptance, maintainability, and cost. Use interim controls while permanent controls are designed.
Worked example
Concrete cutting creates respirable crystalline silica. A respirator-only plan fails the hierarchy. Better: use a wet-cutting saw or on-tool dust extraction as an engineering control, isolate the area and schedule cutting to reduce nearby exposure as administrative controls, and reserve tight-fitting respirators for remaining exposure or tasks where water and dust extraction are not feasible. Verify with personal sampling.
Traps
- Calling training or signage an engineering control.
- Choosing PPE because it is fast, then never evaluating higher controls.
- Assuming one control works for all tasks or all workers.
- Ignoring maintenance and behavior dependence when comparing options.