Fit testing—not just for respirators
Selecting hearing protection devices
Occupational noise exposure is regulated by the Occupational Safety and Health Administration (OSHA) to prevent noise-induced hearing loss among America’s workers. OSHA regulations (29 Code of Federal Regulations (CFR) 1910.95) require employers to implement a hearing conservation program when noise exposure is equivalent to or greater than 85 A-weighted decibels (dBA) over 8 working hours. If employees experience a standard threshold shift or are exposed to noise over the permissible exposure limit, they must wear hearing protection.
Furthermore, if employees are required to wear hearing protective devices (HPDs), those devices must adequately attenuate noise exposure to an 8-hour time-weighted average (TWA) of 85 dBA. To confirm adequate attenuation, many employers use the guidelines in Appendix B to 29 CFR 1910.95, which use the Noise Reduction Rating (NRR) method developed by the Environmental Protection Agency (EPA). The NRR is a laboratory-based method for calculating the amount of attenuation provided by an HPD and must be listed as a label on any HPD packaging.
Issues with the NRR
Although OSHA provides guidance for verifying the attenuation level of a given HPD using the NRR, this method is less than ideal. Because the NRR is based on the average amount of attenuation provided by a device when worn by 10 different people in a laboratory setting, for most wearers, the NRR overestimates the protection offered. Research has consistently shown that in the field, HPDs provide significantly less protection than the NRR estimates.
Additionally, the NRR is calculated using C-weighted decibels, while the permissible exposure limit is in A-weighted decibels. So, to adjust the NRR, OSHA instructs employers to subtract 7 from the NRR before subtracting the remainder from the measured TWA. When it comes to enforcement, OSHA has issued guidelines for inspectors to derate the NRR by 50% (divide by 2) to determine an HPD’s relative performance. This creates quite a bit of confusion when selecting the appropriate HPD for employees.
Finally, if using the NRR to verify adequate attenuation, employers will undoubtedly end up with some employees who are not adequately protected and others who have more protection than truly needed, which can make it difficult for them to hear voices, alarms, or other important noises in the workplace.
Hearing protection fit testing
Although fit testing for HPDs is relatively new, there are multiple methods available, such as subjective real-ear attenuation at threshold (REAT) measurements, objective field microphone-in-real-ear (F-MIRE) measures, and loudness balance technologies, to obtain a personal attenuation rating (PAR). Unlike the NRR, fit testing can determine the true attenuation for each individual employee and allows for the selection of the best HPD for that employee and the employee’s work environment. Performing fit tests for HPDs is also a good training tool because employees will learn how to properly wear HPDs by learning “what right feels like.”
A successful hearing conservation program selects HPDs that provide the right level of attenuation based on employees’ communication needs, hearing ability, convenience, compatibility with other personal protective equipment (PPE), and the environment where they will be worn. But most critically, the right HPD is the one that an employee will wear 100% of the time the employee is exposed to noise. Consider implementing a hearing protection fit-testing program for selecting the appropriate HPDs and more effectively protecting employees’ hearing.
