Physical Environment
Noise
Noise causes permanent hearing damage, interferes with speech and warning signals, and adds to fatigue and irritation. Hearing loss from noise is irreversible, so prevention is the only protection. As a rough field guide, if you have to shout to be understood at arm's length, the level is high enough to require protection and assessment.
Lighting
Problems are not only too little light but glare, poor contrast, deep shadows, flicker and poor colour rendering. Fine inspection and colour-critical work need higher levels and good colour rendering. Moving between a bright ramp and a dark hangar causes adaptation delays during which errors are likely.
Climate and motion
Heat causes dehydration, heat stress, rash and slower decisions; cold causes numbness, loss of dexterity and, eventually, hypothermia. Vibration and whole-body motion cause discomfort, nausea and degraded fine control.
Altitude and confined spaces
At altitude, hypoxia degrades judgement, coordination and night vision before the person is aware of it, and the effects are worse for smokers. Confined spaces require atmosphere testing and a rescue plan before entry.
Traps
Believing hearing loss is temporary or that people adapt to noise; believing heat only affects comfort, not error rate. Also confusing illumination quantity (lux) with quality (glare, contrast, colour).
Rule of thumb: when a question asks for the first response to an environmental hazard, protective controls and removing the person from exposure come before PPE.