Work Environment Assessment, Hazard Recognition, and Exposure Control
Recognize, evaluate, control
This domain is the technical heart of OHN practice. Know the hierarchy of controls: elimination, substitution, engineering controls, administrative controls, and personal protective equipment (PPE) - with PPE last because it depends on human behavior and fit. Understand the industrial hygiene process: anticipate, recognize, evaluate, and control. Candidates should recognize major hazard classes: chemical (solvents, dusts, gases), physical (noise, vibration, heat, radiation), biological (bloodborne pathogens, TB, mold), ergonomic (repetition, force, posture, lifting), and psychosocial (stress, violence, shift work).
Exposure concepts
- Routes: inhalation, dermal, ingestion, injection.
- Dose-response and exposure limits (PELs, TLVs, RELs) - know that a limit is not a guarantee of safety for all workers.
- Sampling: personal versus area, and time-weighted averages versus short-term limits.
- PPE essentials: respirator fit testing and medical clearance, glove selection and compatibility, donning/doffing.
- Noise: hearing conservation, dosimetry, and the 85 dBA action level concept.
Traps
Questions test whether you reach for the highest control feasible. Choosing "provide PPE" when engineering controls are possible is a classic wrong answer. Another trap: confusing area sampling with personal exposure, or assuming a compliant exposure level means no risk. Also watch for questions about respirator medical clearance - the nurse evaluates, but the provider clears.
Rule of thumb
When a hazard is identified, move up the hierarchy: can we eliminate or substitute? If not, engineer it out. Administrative and PPE controls are the last layers, not the first.