What are the goals of your Hearing Conservation Program? They should include the following:
Field monitoring systems, such as FitCheck, are especially important for insert-type HPDs. Assumed protection based on the NRR for insert-types can be wildly inaccurate. Actual protection in the field may be zero, or it may exceed the attenuation data provided by the manufacturer. And, assumed protection based on the NRR leads to a "more is better" attitude, which compromises communication and related safety issues. Effective use of HPDs, especially insert-types, requires measurement of the attenuation provided to the individual wearer in order to adequately address the issues of initial HPD selection, training, fitting and communication requirements. In a 1998 steel industry study involving 389 steelworkers, workers who chose insert-type protectors were individually fit-tested using FitCheck. A specific silicone reusable HPD was chosen by 192 workers, and 85 others chose a specific urethane foam plug. The graphs below show the Personal Attenuation Ratings (PARs) initially achieved by these workers.  
Initially, all of the wearers participating in the retest had PARs of less than 8dB. After training and retesting, more than 60% of these same wearers achieved PARs of greater than 15dB. The average improvement was 14 dB. 
Communications and comfort are major issues with the wearers of HPDs. These issues directly pertain to wearing time, which dramatically and adversely affects overall HPD performance. Uncomfortable HPDs, or those that don't allow communication or necessary job-related hearing, are likely to be removed often. Even temporary removal leads to rapid and non-linear degradation of HPD performance. 
Comfort, wearing time and communications compatibility are related design concepts. The solution is to select appropriate HPDs, not just those with the highest NRRs.
The FitCheck and CHiPS systems allow the Hearing Conservationist to verify that each HPD wearer is using an appropriate HPDs according to EN 458 guidelines. This is especially critical for HPD wearers who already have some hearing loss. FitCheck also provides legal defense based on the documentation of effective HPD management. Initial HPD selection, training, fitting and communications requirements can all be verified and documented. This shifts responsibility for proper wearing to the employee, and provides a "personalized" element to your Hearing Conservation Program. Everyone wins in this scenario. The HPD wearer is safer and better protected, and industry is provided with a defense against hearing loss compensation. FitCheck features:
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FitCheck provides the means for Hearing Conservationists to achieve these goals for users of insert-type HPDs. FitCheck utilizes custom-designed hardware and specially-designed headphones to replicate the ANSI standard laboratory attenuation measurement procedure. FitCheck is practical and convenient to integrate into your annual audiometry program. Testing an end-user requires only about seven minutes.
In December of 1998 105 of the insert-type HPD wearers were retested. These individuals were selected because the attenuation measured during the initial test was low. Each wearer was retested with their HPD of choice. This test was followed by a brief period of retraining (literally only 2-3 minutes), refitting and then retested. The results are shown in these graphs.
But what is appropriate? The EN 458 Guidance Document is the only standards-type document to address the issue of HPD selection for specific noise environments.