Two case studies for fit testing hearing protector devices

Hearing protection devices (HPDs) are typically selected based upon the Noise Reduction Rating (NRR) and, until recently, were rarely tested for attenuation in real-world environments. The National Institute for Occupational Safety and Health has developed a fit-testing system (HPD Well-Fit™) that performs attenuation tests with a large circumaural earmuff, a portable computer and a computer mouse with a scroll wheel. HPD Well-Fit was used to estimate the attenuation of employees working in two different settings: inspectors for off-shore drilling rigs and sandblasters at a hydroelectric facility. The highest exposure levels for the inspectors and sandblasters were estimated to be 110 and 130 dBA, respectively. Fit testing and training were used to achieve a 25-dB Personal Attenuation Rating (PAR) for the inspectors. Fit testing before and after the sandblaster work shift demonstrated PARs of 30 to 42 dB using HPD Well-Fit. The average time to complete the fit tests was 10 minutes. If retraining was necessary, then an additional 3 to 6 minutes were required.