Welcome to Safety Watch, a newsletter that provides an update on current loss-control regulatory and technical issues.

CONTENTS

Beware when driving near large trucks (cover page)

Employees' off-the-job injuries can be very costly to employers

Online training can help streamline your operations

Methods for selecting proper hearing protectors

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Methods for selecting proper hearing protectors

by Kin H. Yu, CIH

The National Institute for Occupational Safety and Health publishes a helpful hearing protector compendium, including products from 23 manufacturers nationwide. This online compendium can be accessed from the Web site www.cdc.gov/niosh/topics/noise/hpcomp.html.

One primary concern facing a company safety manager when establishing a Hearing Conservation Program is to select hearing protectors that adequately protect all employees in the program.

Currently, the main criteria for selecting hearing protectors is based on the Noise Reduction Rating (NRR) printed on the package label. The NRR label is required of the hearing protector manufacturer by the U.S. Environmental Protection Agency (EPA).

There are several methods to calculate and determine if the hearing protector selected will reduce noise exposure to below 90 dB for an eight-hour Time Weighted Average (TWA) or below an 85 dB eight-hour TWA.

In Appendix B of the current Occupational Safety and Health Administration Noise Standard 29CFR1910.95, four methods are described:

1. Using dosimeters that are capable of C-weighted measurements, obtain the employee’s C-weighted full shift TWA. Subtract the NRR from the C-weighted TWA to obtain the estimated A-weighted TWA under the ear protector. In using this method, however, two dosimeters, one set to measure at the A-scale and the other at the C-scale, are required during noise exposure evaluation.

2. When using a dosimeter that is not capable of C-weighted measurements, subtract 7 from the NRR. The 7dB correction is based on the assumption that there will be a 7dB difference in the C-weighted and A-weighted measures of the same noise. Subtract the remainder from the A-weighted TWA to obtain the estimated A-weighted TWA under the ear protector.

3. Same as method 2, except use a sound-level meter to estimate the TWA.

4. Same as method 1, except use a sound-level meter to estimate the C-weighted average sound level and subtract the NRR from the C-weighted average sound level to obtain the estimated A-weighted TWA under the ear protector.

In-the-field and laboratory ratings differ

The following is another method in the OSHA Technical Manual to estimate noise attenuation under the ear protector: The 50 percent factor is an adjustment made to account for the difference between a laboratory-determined NRR and the actual noise reduction achieved in the field due to field-use losses.

The National Institute for Occupational Safety and Health (NIOSH) in its revised criteria document suggests that an NRR derating procedure be used to estimate the protected Exposure Noise Level (ENL).

It is suggested the labeled NRRs be derated as follows: Ear muffs: Subtract 25 percent from the manufacturer’s labeled NRR. Foam plugs and custom-molded ear plugs: Subtract 50 percent from the labeled NRR. All other ear plugs including semi-inserts: Subtract 70 percent from the labeled NRR.

The effective ENL = dBA-(derated NRR-7)

The widely used NIOSH method for foam plugs is the preferred and most conservative method.

Hearing protector database is online

The NIOSH has a hearing protector database, called the Hearing Protector Devices Compendium, on its Web site at www.cdc.gov/niosh/topics/noise/hpcomp.html. The compendium contains data as of June 2003 from 23 manufacturers nationwide and is said to represent a majority of the market share.

The database is viewable and printable, as is the tutorial on how the NRR and other rating systems are calculated.

In the end, choose the method that works best for your application and offers appropriate hearing protection to your employees.

For assistance or more information on this topic, please contact:

Jeff Milosch, CIH
NATLSCO Risk and Safety Services
Phone: 888-576-7522, ext. 3725
Fax: 847-726-3349
E-mail: jmilosch@us.bureauveritas.com