How can I protect my hearing at work?
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Back to topThe surest method of preventing noise-induced hearing loss (NIHL) is to eliminate the source or to reduce noise at the source by engineering methods. However, in certain situations, these measures are not possible. In such workplaces, workers may need to wear hearing protectors to reduce the amount of noise reaching the ears.
What are some things I should know about selecting hearing protection devices?
Back to topPeople should wear a hearing protector if the noise or sound level they are exposed to is close to or greater than the occupational exposure limits (OEL) for noise. For most jurisdictions, this occupational exposure limit is 85 decibels (A-weighted) or dBA. Hearing protectors reduce the noise exposure level and the risk of hearing loss when worn correctly.
If hearing protection is required, then a complete hearing conservation program should be implemented. A hearing conservation program includes noise assessment, methods for controlling noise, hearing protector selection, employee training and education, audiometric testing, maintenance, inspection, record keeping, and program evaluation.
The effectiveness of hearing protection is reduced greatly if the hearing protectors do not fit properly, are not inserted or worn correctly, if they are worn only periodically, or if they are removed even for a short period of time. To maintain their effectiveness, the hearing protection should not be modified. Music earphones or headsets are not substitutes for hearing protectors and should not be worn where hearing protectors are required to protect against exposure to noise.
Select hearing protection that is:
Earplugs are inserted in the ear canal. They may be premolded (preformed), moldable, rolldown foam, push-to-fit, or custom molded. Disposable, reusable and custom earplugs are available.
Semi-insert earplugs consist of two earplugs held over the ends of the ear canal by a rigid headband.
Earmuffs consist of sound-attenuating material and soft ear cushions that fit around the ear and hard outer cups. They are held together by a headband.
The choice of hearing protectors is a very personal one and depends on a number of factors including level of noise, comfort, and the suitability of the hearing protector for both the worker and the environment. Most importantly, the hearing protector should provide the desired noise reduction. It is best, where hearing protectors must be used, to provide a choice of a number of different types and sizes to choose from.
If the noise exposure is intermittent, earmuffs are more desirable since it may be inconvenient to remove and reinsert earplugs.
Manufacturers provide information about the noise-reducing capability of a hearing protector, referred to as an NRR (noise reduction rating) value. The NRR is based on laboratory conditions, therefore, calculations to de-rate the noise reduction rating should be done to reflect workplace conditions (see further below).
CSA Standard Z94.2-14 (R) 'Hearing protection devices ' Performance, selection, care, and use' defines noise reduction rating as 'a single number rating that indicates the overall hearing protector attenuation, computed as the difference between the overall C-weighted level of a noise spectrum having equal energy per octave and the A-weighted noise levels under a hearing protector, using mean attenuation data less two standard deviations, derived from the experimenter-fit-procedure of the edition of ANSI Z3.19 (withdrawn) as defined in EPA ()'.
The NRR, or other similar systems such as the single number rating (SNR), is a method to more accurately determine the effective exposure of a person when wearing a hearing protector. These rating systems attempt to estimate the actual sound protection provided by hearing protectors when worn in actual working environments (vs. laboratory testing situations). The 'real world' results are often different than laboratory tests with the main reasons for this difference being poor fit, and lack of proper training, supervision, and enforcement. For these reasons, training on the correct fit, and making sure users have a thorough understanding of hearing loss are important elements of the hearing conservation program.
Detailed calculations of the protection provided by a hearing protector involve using octave band analysis of the workplace noise and the noise attenuation provided by the hearing protector for noise in each octave band. Attenuation is defined by CSA Standard Z94.2-14 (R) 'Hearing protection devices ' Performance, selection, care, and use' as 'the reduction in sound pressure level incident upon the ear due to the application of a hearing protector or, specifically, the change in hearing threshold level that results when a hearing protector is worn.'
Calculating noise attenuation of hearing protection and de-rating noise reduction values (NRR)
Source: CSA Z94.2-14 (R) 'Hearing protection devices ' Performance, selection, care, and use' Table 2
Earplugs
Percent of NRR achieved: 50%
For use with dBA: Leq ' [NRR (0.50) ' 3] = XX dBA
For use with dBC: Lceq ' NRR (0.5) = XX dBA
Earmuffs
Percent of NRR achieved: 70%
For use with dBA: Leq ' [NRR (0.7) ' 3] = XX dBA
For use with dBC: Lceq ' NRR (0.7) = XX dBA
Dual Protection (use of earplugs and earmuffs)
Percent of NRR achieved: 65%
For use with dBA: Leq' [(NRR + 5) (0.65) ' 3] = XX dBA
For use with dBC: Lceq ' (NRR + 5) (0.65) = XX dBA
The NRR used for dual-protection calculations is higher of the individual NRRs of the two devices.
Note: Certain CSA Group standards are available for online viewing. To access these, you must first create an account with 'CSA Communities'.
Go to: "https://community.csagroup.org/login.jspa?referer=%252Findex.jspa"
Once you are logged in, click on the text below the 'OHS Standards / View Access' graphic.
Click on the jurisdiction of your choice to see the CSA Standards as referenced in that legislation.
Standards may also be purchased from CSA Group: "https://store.csagroup.org/"
As an example:
Measured workplace noise time-weighted average (TWA) exposure = 98 dBA
Earplug with NRR = 29 dB
Estimated noise exposure = 98 ' [29(0.5) - 3] = 86.5 dBA
CSA Standard Z94.2-14 (R) provides further guidance on how to apply NRR calculations.
Both types of hearing protection offer advantages and disadvantages.
Earplugs can be mass-produced or individually molded to fit the ear. They can be reusable or disposable. On the positive side, they are simple to use, less expensive than muffs, and often more comfortable to wear when in hot or damp work areas. Some disadvantages are they provide less noise protection than some muffs, and should not be used in areas exceeding 105 dBA. Earplugs are less visible than muffs, making it more difficult to confirm if they are worn. They must be properly inserted and inserted hygienically to provide adequate protection.
Earmuffs can vary with respect to the material and depth of the dome and the force of the headband. The deeper and heavier the dome, the greater the low-frequency attenuation provided by the protector. The headband must fit tightly enough to maintain a proper seal, yet not be too tight for comfort. Some advantages are that earmuffs usually provide greater protection than plugs, although this is not always true. They are easier to fit, generally more durable than plugs, and they have replaceable parts. On the negative side, they are more expensive and often less comfortable than plugs, especially in hot work areas. In areas where noise levels are very high, muffs and plugs can be worn together to give better protection.
The following table summarizes the differences between earplugs and earmuffs.
Comparison of Hearing ProtectionEarplugsEarmuffsAdvantages:
Advantages:
may be worn with minor ear infections
Disadvantages:
Disadvantages:
The human aspects of hearing protection are particularly important since the only useful kind of protection is the protection that is actually worn. Some people do not accept particular kinds of protectors; every human being is different, and the anatomy of the ear and ear canal can vary significantly from person to person.
It is a good idea for the employer to provide a number of different types and sizes of hearing protection from which workers can choose, keeping in mind any safety or hygienic reasons for not providing a particular kind of protector. That is, a particular type of protector should not be used if noise levels are too high or if it proves to be inadequate from a hygienic point of view. For example, earplugs which are used in a plant setting where people reuse them throughout the day, often reinserting them with dirty fingers, can introduce dirt and bacteria into the ears, causing ear infections.
The bottom line on hearing protection is worker preference. If the workers do not like the type of protection (for example, if it is uncomfortable, does not fit well, or is impractical), they will not wear it.
Follow the manufacturer's instructions. With earplugs, for example, the ear should be pulled outward and upward with the opposite hand to enlarge and straighten the ear canal, and insert the plug with clean hands.
In order to get the full benefit, hearing protectors must be worn all the time during noisy work. If hearing protectors are removed only for a short duration, the protection is substantially reduced. The following table gives a maximum protection provided for non-continuous use of an ideally fitted 100% efficient hearing protector. For example, when hearing protection is rated with an attenuation of 25dB, if one takes off their hearing protector for 5 minutes in an hour the maximum protection will be reduced to no more than 11dB.
Impact of removing hearing protectorTime removed (in 1 hr)Maximum 25 dB protection is reduced to (dB)0 minno reduction1 min175 min min830 min360 min0Source: Removal of hearing protectors severely reduces protection. Health and Safety Executive, UK (no date)
Hearing protectors must be used ALL THE TIME to get the full benefit.
A hearing protection device, also known as a HPD, is an ear protection device worn in or over the ears while exposed to hazardous noise and provide hearing protection to help prevent noise-induced hearing loss. HPDs reduce the level of the noise entering the ear. HPDs can also protect against other effects of noise exposure such as tinnitus and hyperacusis. There are many different types of HPDs available for use, including earmuffs, earplugs, electronic hearing protection devices, and semi-insert devices.[1]
The use of the HPD without individual selection, training and fit testing[2] does not significantly reduce the risk of hearing loss.[3][4] For example, one study covered more than 19 thousand workers, some of whom usually used hearing protective devices, and some did not use them at all. There was no statistically significant difference in the risk of noise-induced hearing loss.[5]
Exposure limits
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In the context of work, adequate hearing protection is that which reduces noise exposure to below 85 dBA over the course of an average work shift of eight hours.[6]
When sounds exceed 80 dBA, it becomes dangerous to the ears. The National Institute for Occupational Safety and Health (NIOSH) has standards that show how long a person can be in different loudness levels before the person reaches their maximum daily dose and becomes damaging to their hearing. These standards can give individuals an idea of when hearing protection should be considered. The maximum daily dose with the corresponding decibel level is shown below.[7]
dBA
Time reaching maximum daily dose, hours : minutes OSHA,[8]TWA 90 dB(A),
exchange rate 5 dB
NIOSH,TWA 85 dB(A),
exchange rate 3 dB
ISO ,[9]TWA 80 dB(A),
exchange rate 3 dB
80 ' ' 8 : 00 81 ' 20 : 9.5 6 : 21 82 ' 16 : 00 6 : 02 83 21 : 07 12 : 42 4 : 00 84 18 : 23 10 : 4.8 3 : 10 85 16 : 00 8 : 00 2 : 31 86 13 : 56 6 : 21 2 : 00 87 12 : 08 5 : 2.4 1 : 35 88 10 : 33 4 : 00 1 : 16 89 9 : 11 3 : 10 1 : 00 90 8 : 00 2 : 31 48 min 91 6 : 58 2 : 00 38 m 92 6 : 04 1 : 35 30 m 93 5 : 17 1 : 16 24 m 94 4 : 36 1 : 00 19 m 95 4 : 00 0 : 48 15 m 96 3 : 29 0 : 38 12 m 97 3 : 02 0 : 30 9.4 m 98 2 : 38 0 : 24 7.5 m 99 2 : 18 0 : 19 6 m 100 2 : 00 0 : 15 4 m 43 sec 101 1 : 44 0 : 12 3 m 45 s 102 1 : 31 9 min 24 sec 2 m 58 s 103 1 : 19 7 m 30 s 2 m 22 s 104 1 : 09 6 m 1 m 53 s 105 1 : 00 4 m 42 s 1 m 29 s 106 52 m 3 m 48 s 1 m 11 s 107 45 m 3 m 56 s 108 40 m 2 m 24 s 45 s 109 34 m 1 m 54 s 36 s 110 30 m 1 m 30 s 28 s Permissible noise levels in different countries[10] Country TWA, dBA(for an 8-hour shift)
Level increase corresponding to doubling the dose(Exchange rate)
Argentina 90 3 Australia 85 3 Brazil 85 5 Canada 85 & 82[11] 3 Chile 85 5 China 70'90 3 European Union countries 85 3 Finland 85 3 France 85 3 Germany 85, 70, 55[12] 3 Hungary 85 3 India 90 ' Israel 85 5 Italy 85 3 Netherlands 80 3 New Zealand 85 3 Norway 85, 55, 70 3 RF[13] 80 3 Spain 85 3 Sweden 85 3 United Kingdom 85 3 USA 90 (100)* 5 Uruguay 90 3 OSHA issued a directive to inspectors in .[3] They are ordered to stop requiring employers to install engineering noise control if noise dose < 100 dBA. This decision is considered illegal,[14] but it is carried out in practice in most US states.[15]These numerical values do not fully reflect the real situation. For example, the OSHA standard[8] sets the Action Level 85 dBA, and the PEL 90 dBA. But in practice, the Compliance Safety and Health Officer must record the excess of these values with a margin, in order to take into account the potential measurement error. And, in fact, instead of PEL 90 dBA, it turns out 92 dBA, and instead of AL 85 dBA ' 87 dBA.[16]
Different types of hearing protection may be used to maximize hearing protection. OSHA regulations dictate whether hearing protection is required and if the company must participate in a hearing conservation program. But many employers are not implementing these programs effectively, and the risk of hearing loss is not reduced.[3]
Hunting and firearms
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The shooting of guns for recreational use can lead to hearing loss in the high frequencies.[17] The shooting of firearms can cause damage to a variety of cochlear structures due to the high peak sound pressure levels that they generate. This can range from 140 to 175 dB.[18]
Along with the passive noise reduction options usually used vocationally (such as earmuffs and earplugs) there are also active noise reduction devices available. Active noise reduction technology is used to provide noise protection like passive options, but also use circuitry to give audibility to sounds that are below a dangerous level (about 85 db) and try to limit the average output level to about 82 to 85 dB to keep the exposure at a safe level.[19][18]
Strategies to help protect your hearing from firearms also include using muzzle brakes and suppressors, shooting fewer rounds, and avoiding using a firearm with a short barrel. It is recommended to shoot outdoors or in a sound-treated environment, rather than a reverberant environment (an enclosed area with sound-reflecting surfaces). If there are multiple people shooting, make sure there is a large distance between the shooters and that they are not firing at the same time.[18]
Types
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Earmuff hearing protection device.Types of ear protection include:
In some occasions, multiple types of ear protection can be used together to increase the NRR. For example, foam earplugs can be worn in-conjunction with earmuffs.
If you are looking for more details, kindly visit Behind Head Earmuffs.
Each type of ear protection has what is called a noise reduction rating (NRR). This gives the consumer an estimate of how much noise is being reduced before reaching the individual's ear. It is important for the consumer to know that this is only a single number estimate derived from a laboratory experiment, and the NRR will vary per individual wearing the hearing protection. NIOSH and OSHA have derating values to help give the person an idea of how much sound is being attenuated while wearing the hearing protection. OSHA uses a half derating, while NIOSH uses 70% for pre-formed earplugs, 50% for formable earplugs, and 25% for earmuffs.[20]
But all such derating[21] are not consistent with each other, and do not take into account the individual characteristics of the worker.
Country,organization
Earplugs Earmuffs formable pre-formed USA, OSHA Decrease by 2 times Decrease by 2 times Decrease by 2 times USA, NIOSH Decrease by 2 times Decrease by 3.3 times Decrease by 1.33 times Italy Decrease by 2 times Decrease by 3.3 times Decrease by 1.33 times Great Britain 4 dB reduction 4 dB reduction 4 dB reduction France 10 dB reduction 10 dB reduction 5'7 dB reduction Germany 9 dB reduction 5 dB reduction 5 dB reductionTherefore, no derating allows the specialist to predict the noise attenuation of a particular model for a particular worker. That is, the use of laboratory test results (NRR, SNR, HML, ets.) does not predict the effectiveness of the protection of a particular worker,[22] at all.[21] The range of actual values may be, for example, from 0 to 35 decibels.[23]
Earmuffs
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Different styles of earplugs are pictured. Left, pre-molded earplugs. Center, formable earplugs. Right, roll-down foam earplugs.Earmuff style hearing protection devices are designed to fit over the outer ear, or pinna. Earmuff HPDs typically consist of two ear cups and a head band. Ear cups are usually lined with a sound-absorbing material, such as foam. The cups should be fit so that the center of the ear canal aligns with the ear canal opening.[1] The soft cushions seal around the pinna of the ears. The head band, centered at the top of the head, applies force/pressure to seal the ear cups over the ears.[1]
Earplugs
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Earplug style hearing protection devices are designed to fit in the ear canal. Earplugs come in a variety of different subtypes.[1] The attenuation offered by these devices can be measured through hearing protection fit testing.
Electronic hearing protection devices
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Some HPDs reduce the sound reaching the eardrum through a combination of electronic and structural components. Electronic HPDs are available in both earmuff and custom earplug styles. Electronic microphones, circuitry, and receivers perform active noise reduction, also known as noise-cancelling, in which a signal that is 180-degrees out-of-phase of the noise is presented, which in theory cancels the noise.[1]
A U.S. Soldier wearing a hearing protection and communications headset.Some electronic HPDs, known as Hearing Enhancement Protection Systems,[1] provide hearing protection from high-level sounds while allowing transmission of other sounds like speech. Some also have the ability to amplify low-level sounds. This type may be beneficial for users who are in noisy environments, but still need access to lower level sounds. For example, soldiers who need to protect their hearing but also need to be able to identify enemy forces and communicate in noise, hunters who rely on detecting and localizing soft sounds of wildlife but still wish to protect their hearing from recreational firearm blasts, as well as users with pre-existing hearing loss who are in noisy environments may all benefit from In Ear Electronic Hearing Enhancement Protection Systems.[24][1]
Electronic HPDs require the use of batteries and are typically more expensive than non-electronic types.
Semi-insert devices (canal caps)
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Custom earplug hearing protection devices.Canal caps are similar to earplugs in that they consists of soft tip that is inserted into the opening of the ear canal. Some styles are inserted slightly into the ear canal while others sit in place at the opening of the ear canal. In this case, the tips or caps are connected by a lightweight band which also serves to hold them in position.[1]
Dual hearing protection
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Dual hearing protection refers to the use of earplugs under ear muffs. This type of hearing protection is particularly recommended for workers in the mining industry because they are exposed to extremely high noise levels, such as an 105 dBA TWA.[25][citation needed] Fortunately, there is an option of adding electronic features to dual hearing protectors. These features help with communication by making speech more clear, especially for those workers who already have hearing loss.[1]
The sound attenuation of a dual hearing protector is generally lower than the algebra sum of the attenuation of each single hearing protector.[26][27][28] This phenomenon can be caused by the mechanical coupling between the earplug and earmuff through the human tissues, the vibration of the ear canal wall, or the bone conducted sound travelling from the head and body directly to the middle and inner ears.[28][29] As a rule of thumb, the noise reduction rating of a dual hearing protector can be estimated by adding a 5 dB correction factor to the higher noise reduction rating of the two single hearing protectors.[30]
Hygiene and care
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In order to prevent irritation or infection of the ear, reusable HPDs should be cleaned on a regular basis. Before using any HPD, it should be inspected for damage or dirt to ensure that it is safe to use. Single-use, disposable earplugs are available in addition to reusable options.[31] Earplugs intended for single-use should not be washed for reuse as this degrades the material and reduces effectiveness.[32]
Most reusable earplugs can be cleaned using mild soap and warm water between uses and should be replaced every 2'4 weeks.[31] Earmuff cups and cushions should be cleaned regularly with soap and water, and be replaced if they become cracked or otherwise compromised. Ear cushions can last from 3'8 months depending on use.[31] Use of a clean, protective case to store HPDs when not in use is recommended to prevent damage or contamination.[1]
Any damage to a HPD can compromise its integrity, thus reducing its effectiveness. Damaged HPDs should not be used.
Requirements of the law and recommendations of specialists
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Many countries require several interventions to control risks from exposures to loud noise in the workplace. For example, US Occupational Safety and Health Administration requires hearing conservation programs which include the provision of hearing protection devices. This does not mean that OSHA considers HPDs to be effective. In fact, the document[33] directly indicates their unreliability.
It is also recommended by the U.S. National Institute for Occupational Safety and Health, audiologists and other hearing healthcare professionals when one works exposed to noise levels that exceed 85 dB.[1] NIOSH base their recommendations for use of hearing protection by a calculation called time-weighted average (TWA). A time-weighted average is the average noise level a worker is exposed to over a period of time. NIOSH recommends that OSHA use an 85 dBA time-weighted average during an 8-hour period as their exposure limit.[1] An 85 dBA time-weighted average means that HPD use is recommended if an employee is exposed to an average noise level of 85 dBA or more during an 8-hour work day. NIOSH also uses a 3 dB exchange rate for time-weighted averages.[1] A 3 dB exchange rate means that for every 3 dB increase in the average level of noise the recommended time being exposed to that level of noise is cut in half. For example, for a worker who is exposed to 88 dBA, it's recommended he/she only be exposed to that level of noise for 4 hours. These levels of noise may be encountered in both occupational and recreational settings. HPDs are recommended for use in settings where it is difficult to control the noise level, and the person exposed to the noise cannot be removed from the environment.
Noise reduction, earplugs EP100 (Willson). Top: measurements in the laboratory, and performance ratings. Bottom: real-world data[34]The amount of protection from noise can vary based on the physical fit of the device and the skill of the worker.[21] Hearing protection devices with accurate placement (an airtight seal) and/or accurate insertion (deep into the ear canal) will provide the most attenuation of noise.[1] There are many challenges to achieving the needed protection from the device, from barriers to adequate use, to issues related to comfort, convenience, lack of training, to beliefs and attitudes towards its use.[35][36][37][38][39][40]
HPD noise reduction: on label (NRR, SNR, HML, SLC80), and real noise attenuation (at workplaces)
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Hearing protection device manufacturers in the United States are required by the EPA to label HPDs with a noise reduction rating, or NRR. The NRR estimates how much noise is reduced by a hearing protection device, measured in decibels.[1]
The NRR is measured by manufacturers using American National Standards Institute (ANSI) specified procedures in a laboratory environment.[1] But noise attenuation when workers use HPD was much more variable, and much weaker than when they were tested in laboratories. This was shown both by the first two studies (NIOSH)[41][42] and many subsequent works in the different countries[43] (example[23]).
An example of a NIOSH mobile laboratory for measuring sound thresholds, and the real attenuation of workers earplugs[44]There were no technical means to take into account the variability of the HPD noise attenuation in different workers for a long time. For this reason, specialists (NIOSH[20][45] and others) have tried to take at least palliative measures. They recommended that employers estimate the average noise attenuation of workers based on the average noise attenuation of testers in the lab ' with correction (de-rating[4]). However, in fact, the result of such manipulations did not provide any information about the noise attenuation of a particular worker.
The advent of new technologies has solved the problem, and individual measurement of noise attenuation is considered the most promising trend in personal noise protection[46][21] Hearing protection fit-testing has been developed in order to determine the actual attenuation of the device as it is worn for an individual. These tests for checking attenuation values summarize the real-world attenuation in a personal attenuation rating (PAR).[1] The PAR is unique to the HPD tested and the individual wearing the protection, and personal fit testing US OSHA and the National Hearing Conservation Association (NHCA) Alliance recommend that employers conduct individual worker noise attenuation measurements (HPD fit-testing) as a best practice and valuable tool for improving employee training.[47][48]
Unfortunately, such equipment is expensive, and this holds back widespread use of new technology. NIOSH has tried to alleviate the problem by developing a freely available program (online) for evaluating noise attenuation with liners. It can identify workers who do not know how to insert earplugs, or when workers are given such models that do not fit their ear canals.[49][50][44]
Researchers at NIOSH tried to develop methods for predicting noise attenuation in workers in the early s. This attempt was made just before the first measurements of noise attenuation in factories, among workers. The work was carried out under the following conditions
Barry Lempert and Roy Fleming developed three methods[51] These results have been used to develop NRR (SNR). When developing method No. 2, the authors used the available information about the characteristic noise in industry, in the US in the early s,[52] and the difference in the noise levels (dBC and dBA) to take into account its spectrum ' as in the HML method later.
NIOSH fully took into account the significant difference between the real and laboratory effectiveness of personal protective equipment,[53] but other organizations began to recommend similar methods, and they were fixed in state and international standards.[54]
Regulations and standards
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United States
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See also
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References
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For more information, please visit Western Safety Industrial Ear Muffs.