Don’t Turn a Deaf Ear to Hearing Losses
Fire fighting is fraught with hazards; and fire fighters take beatings unfound in other professions. Among these abuses is the noise attack on their hearing. It is a safety responsibility every fire department should address—provide and enforce hearing protection for its members. Here are some avenues for exploring and countering hazardous noise levels.
Of the myraid fire fighters face, one that has drawn some of the least attention and consideration is the problem of hazardous noise levels.
In the past five years, there’s been a growing sensitivity of the problem by individual fire departments, as well as an increasing concern by apparatus manufacturers.
While we do not know the full effects of noise as a psychological stressor in the fire service, we have a pretty good idea of the long-term physical effects.
The National Institute of Occupational Safety and Health (NIOSH) conducted a study to evaluate reported hearing losses from noise exposure in fire fighting operations in the Newburg, N.Y., Fire Department. The summary of this analysis, “Health Hazard Evaluation Report” was released by NIOSH in February 1982.
The environmental testing of apparatus produced noise level ranges from 99 decibels (db) to 116 db in cab areas, and 105 db to 112 db in the jump seat areas. Levels of 91 to 101 db were recorded at pump panels. (For allowable exposure limits, see table 1.) Individually worn sound dosimeters showed that eight-hour time-weighted average noise exposures ranged from 62.3 db to 85.3 db for the sampled fire fighters. (During the sampling period there was one response, a false alarm.)
The medical testing included the participation of 54 fire fighters with an average age of 37.7 years, and an average of 13.2 years of service. Essentially, the testing illustrated that fire fighters at an early age have better hearing than the general population (national norms), but are consistently poorer at the oldest age grouping. According to the NIOSH report, “the hearing examinations conducted . . . showed large hearing losses in the noise sensitive frequencies. A mean loss of 61.8 db hearing loss at 6000 Hz (cycles per sound) after a mean of 29.4 years of fire service experience was found in a group of five fire fighters aged 50 years and up.”
The study also implied that even though high levels of noise are generated, exposure time is insufficient to account for the observed losses. The study suggests further research be conducted in the areas of the “type of noise” a fire fighter is exposed to, as well as to the interaction of noise and other agents (toxins) found in the fire fighter’s environment. The NIOSH report concludes that, “Fire fighters are being exposed to high noise levels in light of the intensity values found during simulated runs, and do show large amounts of hearing loss.” NIOSH has also issued a number of recommendations on noise control/ hearing protection (see table 2).
What about the psychological effects of noise? Noise as a stressor and its effects on fire fighters are very similar to a heart patient’s reaction to the deafening roar of an air chisel or saw. According to published reports, fireground noise is an environmental stressor, and exposure to high noise levels can result in fatigue and adverse cardiovascular effects.
On a related note, a study conducted in the late 1970s by the University of Kansas concluded that fire fighters who were exposed to high noise levels of an unmuffled engine made more decisions than did fire fighters exposed to the lower level of noise of a muffled engine. However, the fire fighters exposed to the lower level of noise made proportionally fewer incorrect decisions.
Fire departments look into hearing
Many fire agencies are becoming more aware of the noise problem and are initiating actions to protect their personnel. According to Tucson, Ariz., Fire Department’s Maintenance Chief Marian Price, the department has been aware of the problem for about 10 years. The department considers the diesel engine the primary source of offensive noise, and has experimented with engine design to reduce noise levels. The department now makes noise levels a standard bid specification. Newer apparatus have thermostatically controlled fans, which reduce fan running time up to 80 percent. (A fan is a major producer of noise on a diesel engine.)
Price further states that the department’s main control of engine noise has been through an innovative, commercially available muffler. The component is actually two mufflers in one. That is, the muffler has a series of wraps with insulating material. Price’s philosophy on engine design relative to noise control is to specify a “good-size engine and then derate it.” This will allow the engine to run easier and quieter at various load requirements.
The Tucson Fire Department also has relocated roof air horns and speakers to front bumper mounting areas, and has purchased its own noise level reading instrument to periodically monitor apparatus noise levels (see table 3).
The Anaheim, Calif., Fire Department spends almost $800 per apparatus on insulation. Called Varyfol, the insulation reduces noise levels in cab and jump seat areas from engine and warning device operations. Varyfol is a hard rubber material with a lead-based content that provides an excellent shielding quality to battle sound penetration. The heaviest amount of insulation is applied to the inside roof of the cab, because of the warning devices located on top of the cab. Captain Jeff Bowman, services officer for the department, reports the continually monitoring and recording of noise levels produced by each apparatus. Records of noise-pressure surveys predicted upon complaint or discovery of possible noise hazard, must be maintained as permanent records and submitted to the California Division of Industrial Safety upon request.
To determine the effectiveness of the lead-lined insulation material, the Anaheim Fire Department made comparison surveys of pieces with and without the material. The surveys indicated lower noise levels in apparatus equipped with the lead-based insulation.
Time-Weighted Average Noise Limits As A Function of Exposure Duration
* No tx}H*>ur( to continuous noise abox*e l15 db
* * So exposure to impact or impulse muse above 140 Jb peak sound pressure level
Source NIOSH and OSHA
The Jacksonville, Fla., Fire Department has also enacted a program to protect the hearing of its members. The program includes noise analysis monitoring, an educational program on hearing loss, the distribution of protective hearing devices, a call for the cessation of indiscriminate siren use, headset communications, and other actions.
The Los Angeles City Fire Department has probably undertaken the largest effort to date in terms of expanding resources to identify hazardous noise level areas/producers and the subsequent protection of fire personnel.
At presstime, the effort was approximately half completed. The bulk of the program, contracted to a private agency named VECTOR, involves hearing examinations for each member of the department’s 3000 members. Under the guidance of Dr. Henry Schmitts, tests have shown that:
- About 66 percent of the fire fighters have some evidence of highfrequency hearing loss.
- One hundred sixteen out of 3000 fire fighters have conversational hearing loss, and another 150 have a definite need for hearing protection.
- Approximately 25 fire fighters were fitted with hearing aids.
- One fire fighter, upon examination, was found to have a tumor in the inner ear. Without the examination, the lack of such discovery could have been serious.
- The production of sound also is being looked at closely. Some of these preliminary findings include:
- “Bell-type speakers” are either being replaced or repositioned since they are a source of high noise levels.
- New apparatus have specifications requiring sound level maximums.
- Fire stations located near airports, freeways, industry, etc., are being soundproofed.
- The “bleed-off” release of air pressure on air compressor operations is viewed as a creator of hazardous noise levels.
Both VECTOR and the Los Angeles City Fire Department plan to offer information when the full extent of their program is completed.
Manufacturers becoming noise conscious
It would appear that individual fire departments are not the only ones concerned w’ith the apparatus/noise problem. Some apparatus manufacturers are also concerned, and have initiated design characteristics to reflect a goal of quieter apparatus. At first glance, this may seem a bit unusual, as the national standard for automotive fire apparatus (NFPA Standard 1901) currently gives no reference to sound attenuation of noise control. It is basically the demands of fire departments that are causing the design change.
According to Drew Sutphen of Sutphen Fire Apparatus, approximately 40 percent of the pieces they are currently building (or will build) have some specification relative to sound or noise production. Sutphen also states that there is an inherent benefit in selecting a turbocharged diesel engine as opposed to a naturally aspirated engine—the turbocharged engine runs 4 to 5 db quieter. His firm is striving for a maximum 84 db reading within the cab, and a 78 to 90 db maximum level in the jump seat area. To achieve this goal, the firm is utilizing various sound dampening materials, including a pleated foam liner. Sound level readings are monitored every six months on apparatus by the manufacturer.
Gordon Barr of American LaFrance also reports that there is a greater awareness of the noise problem from its buyers. American LaFrance offers an optional package of sound deadening material that is installed in cab and engine areas. The sound deadening material is an attempt to meet sound level requirements of any particular fire department. Another specification item is an “engine blanket.” The blanket, which shields the engine compartment area, is primarily a heat control device, but it also assists in the insulation of sound.
Thus, when one examines the efforts of some individual fire agencies and fire apparatus manufacturers, there is certainly more awareness of the noise problem and its potential than there was five years ago. It is evident that the main source of hazardous noise levels in the fire service is the apparatus itself, and new designs and modifications are being implemented for quieter fire apparatus.
A Summary of NIOSH Recommendations On Noise Control/Hearing Protection
—Limit the use of warning devices as much as legally and practically possible.
—Relocate warning devices from roof or high areas to low apparatus areas, such as running boards, bumpers.
—Reduce warning device intensity to the lowest level at which they are still effective of alerting traffic.
—Replace narrow-band, high frequency devices (mechanical sirens) with broad band, low frequency sirens (electronic, 2-tone). High frequency tones will reflect rather than penetrate other vehicles. Lower frequencies have much less reflection.
—Add sound absorbing material to cab and jumpseat apparatus areas.
—New apparatus specifications should include consideration towards the frequency and intensity of the noise that the vehicle emits.
—Provide personal, protective hearing devices until noise levels of apparatus are or can be reduced. (Ear muffs are preferred.)
—Integrate communications with ear muffs.
—Implement a hearing conservation program for fire fighters.
Any source of intense noise, such as chain saws, gasoline combustion engines or heavy machinery, may damage the inner ear. Individuals vary greatly in susceptibility to noise-induced hearing loss, but nearly everyone will lose some hearing if exposed to sufficiently intense noise for a sufficient time.
Sound is measured by frequency and intensity. Frequency, or pitch, is the number of sound waves per second produced by a sounding body. Hearing loss occurs first at 4000 Hz (cycles per second) and gradually moves into the lower frequencies with further exposure, according to the Merck Manual, a medical publication.
Intensity, the loudness or softness of a noise, is expressed in decibels. According to the Merck Manual, any noise greater than 85 db is damaging. Air chisels and gasoline-powered circular saws are said to produce noise levels of 110 to 120 db. If a 2000-psi gas line ruptures, fire fighters can be confronted with a noise level of 140 db, which exceeds the noise level of a jet plane.
Hearing loss is usually accompanied by a high-frequency tinnitus (ringing in the ears), which can also be reported as a buzzing, whistling, hissing, or roaring.
As reported in the Merck Manual, prevention of hearing loss depends on limiting the length of exposure, reducing the noise at its source, and isolating the person from the sound source. Noise may be attenuated by wearing ear protectors.
One might feel that when the day arrives and all apparatus are within safe noise level limits, there will no longer be a need for personal protection, such as earmuffs or plugs. Th is is a false assumption. There will always be a need for personal protection when operating power tools such as saws, chisels, expansion equipment, and when conducting fire operations around aircraft, releases of pressurized gases, and so forth.
The overall concern of designing an effective protective envelope for the fire fighter (relative to hearing) is not to restrict the fire fighter’s ability to hear and therefore communicate. The performance criteria for the helmet ensemble designed by the U.S. Fire Administration’s Project FIRES (Firefighters Integrated Response Equipment System) called for noise reduction of no more than 10 percent. The prototype was designed around communicative ability. Most helmets on the market today meet this criteria.
Based on my research, there appears to be some controversy over the selection of the type of personal protective hearing equipment. Audiologists normally classify such devices into one of four categories:
- Enclosure—a device such as a helmet. Noise reduction is achieved through the acoustical properties of the helmet.
- Aural inserts—normally referred to as earplugs. Service lives are limited, and some individuals may be unable to wear these.
- Superaural—such as wax plugs, dry cotton plugs and expandable plugs. Preparation and insertion must be completed by trained personnel. These are time-consuming and generally expensive.
- Circumaural—normally called earmuffs. These are easily applied, durable, visible and economical.
The departmental use of any hearing protection device should be in concert with a complete hearing conservation program. This includes discussion of the problems with a trained audiologist. Many cities and areas have hearing centers where this service may be free of charge. Medical centers, hospitals, or even industry are normally willing to provide assistance in the form of analysis and recommendations.