Health hazard evaluation report: HETA-2007-0235-3064, evaluation of potential noise hazards to mechanics and 911 dispatchers at a fire department, Anchorage, Alaska.
On April 24, 2007, NIOSH received an HHE request from AFD management to assess whether the fire department's mechanics should be enrolled in an HCP, and to determine if feedback noise (or "squeal") that the 911 dispatchers heard through their headsets was hazardous to their hearing. A NIOSH investigator visited the site to collect full-shift noise exposures on the mechanics, to interview the 911 dispatchers about their work environment, to measure noise levels in the dispatch area, and to review employee records pertinent to noise and hearing loss. NIOSH investigators also purchased headsets similar in manufacturer and model to those worn by AFD dispatchers for laboratory analysis in-house, and tested actual feedback noise recordings provided by the AFD. Five AFD mechanics provided eight full-shift measures over two days. Five measures exceeded the NIOSH REL. One measure exceeded the OSHA AL; none exceeded the OSHA PEL. The primary source of noise exposure for the mechanics was a ½" impactor gun used to change tires on fire trucks. Of the seventeen 911 dispatchers who were present at the time of the NIOSH evaluation, 15 were interviewed. Nearly all expressed dissatisfaction with their work environment. Their main concerns were the temperatures in the work area (either too cold or too hot), uncomfortable chairs, and the distracting background noise (from visitors, alarms, etc.). When compared to noise criterion curves, noise levels in the dispatch area were higher than recommended for a communications center. The headsets were adequate for their intended purposes, although the H251N had the best linear response between 150 Hz and 2000 Hz and thus provided the best sound quality. Analysis of eight feedback noise recordings produced average noise levels from 68 to 78 dB; the peak sound levels were between 84 and 100 dB. Although average levels were below the NIOSH REL, prolonged exposure to peak sound levels found in the recordings may result in dispatchers developing transient symptoms, such as headache, fatigue, and ringing in the ears, that are associated with exposure to high sound levels. The high noise levels experienced by AFD mechanics warrant enrollment in a hearing conservation program. Also, AFD management, with employee input, should increase awareness among firefighters and other personnel who use radios of the effect of feedback noise on the 911 dispatchers. Management should consider either building a communications center designed for communications work or modifying the existing space.
Region-10; Noise; Noise-exposure; Hearing-loss; Hearing-impairment; Hearing-conservation; Noise-induced-hearing-loss; Mechanics; Communication-workers; Dosimetry;
Author Keywords: Fire protection; feedback noise; 911 dispatchers; mechanics; dosimetry; acoustical mannequin; balanced noise curve; room acoustics; communications cente