Heavy Equipment Operator (HEO) and Skilled Labourer - Final Report - Part I - Essential Skills & Employability Skills, Part II

Worker hearing ability. Workers with hearing impairment may find HPDs reduce sound levels too much and interfere with normal communication, backup alarms, etc.
Communications demands on workers - frequent verbal communications may be affected by HPDs
Use of other personal protective equipment - respirators, safety glasses
Temperature and climate
Work activity
Physical restraints