FAQ / Frequently Asked Questions

FAQ – Hearing Protection and Noise

FAQ – Eye Protection

FAQ – Face Protection

FAQ – Chainsaw Leg Protection

FAQ Hearing Protection

  1. What type of hearing protector do I need for my work environment or hobby?
  2. What are some typical noise levels of sounds and noises in our environment?
  3. How does exposure time affect my hearing protector requirements?
  4. What exposure limits are established for impact noise (such as gun fire)?
  5. How do I select a hearing protector with adequate attenuation for my noise situation?
  6. What are the advantages of earmuffs over earplugs and vice versa?
  7. What is the effect of dual protection? (Use of both earmuffs and earplugs).
  8. How is the attenuation for hearing protectors measured?
  9. What does the NRR (noise reduction rating) mean?
  10. What factors, other than the noise level, combine to create a hearing damage?
  11. Can I still hear the machinery and warning signals, when I use a hearing protector?
  12. Can electronic hearing protectors help improve the ability to hear and communicate in noisy environments?
  13. Is it safe to listen to FM Radio earmuffs when you work?
  14. Who pays for my hearing protection at work?
  15. How do I know if I have a hearing damage?
  16. What can I do if I already have an existing hearing damage?


What type of hearing protector do I need for my work environment or hobby?

You have to consider the following factors, the noise level, the exposure time, and the comfort and ease of use of the protective device. First, you have to select a hearing protector that has adequate attenuation for your work environment. Second, you have to consider how you are going to use the protector. You may for instance choose a different protector if your use is intermittent, requiring you to take on and off the protector frequently, than if you are going to work a continuous eight hour shift in a noisy environment. An earmuff may be preferable in the intermittent environment, while an earplug may be the choice in a long-term exposure. An earmuff may be preferred in a cold environment, while an earplug may be the choice in a hot and humid environment. However, there is no right or wrong choice, as long as you chose a hearing protector with adequate protection, and you use it correctly for the entire exposure time.

What are some typical noise levels of sounds and noises in our environment?

Below is a list of noise levels for sounds and equipment that you may be familiar with. Many of the examples are from the NIOSH website, but other references have also been used. It is important to keep in mind that you should really be concerned with the noise level at the ear, instead of the noise that is actually produced by the equipment. Therefore many of the examples have to be used with thought. For instance few consumers will be close to a jet engine or a fire engine siren, and their exposure is potentially more irritating than damaging. On the other hand, airport and fire engine personnel may indeed be exposed to the sound levels in the table below.

Sound or noise example  

Typical sound level

Comments  

Weakest sound heard by average human ear

0 dB

This is a matter of definition
Rustle of leaf 20 dB

-

Whisper 30 dB

-

Normal conversation 60 dB

-

Inside passenger car at 60 MPH 65-75 dB Smaller cars are usually noisier
Ringing telephone 80 dB Measured close to the phone
Hair dryer 85-90 dB Measured close to the dryer
Lawn mower 85-90 dB Measured at the ear
Maximum exposure, 8 hours   90 dB   OSHA regulation  
Chain saw 90-100 dB Measured at ear, sound level varies by model
Tractor, bulldozer 95-105 dB Inside cab may be less noisy. Sound level varies by model.
Rock drill 110-115 dB

-

Circular saw, table saw 110 dB

-

Threshold of pain   120 dB   A matter of definition  
Pneumatic chipper 120 dB

-

Fire engine siren 120 dB

-

Jet engine at takeoff 140 dB

-

12-gauge shotgun 165 DB Impact sound uses a different risk criteria.
Rocket launch 180 dB

-

Loudest possible sound 194 dB

-


How does exposure time affect my hearing protector requirements?

 The hearing damage criteria established by the OSHA noise regulation takes into consideration the noise level and the exposure time. An exposure to 90 dB for eight hours is considered to be safe by OSHA, but it is recommended that you always use hearing protection when exposed to 100dB or more, even if the exposure is short. The exposure is doubled for every increase of 5 dB, as defined by OSHA. (Physically the sound pressure level doubles every 3 dB). The table below will explain the relationship between noise level and exposure time.

Noise level   Maximum exposure time   Comment  
90 dB 8 hours

-

95 dB 4 hours

-

100 dB 2 hours

-

105 dB 1 hour Always use hearing protection, any exposure
110 dB 30 minutes Always use hearing protection, any exposure
115 dB 15 minutes Always use hearing protection, any exposure

Read more about this issue, “Facts about Permissible Noise Exposure”.

Read a summary of OSHA’s Hearing Conservation Regulation!

What exposure limits are established for impact noise (such as gun fire)?

U.S. Military Standard 1474D, Requirement 4 deals with impact noise and establishes risk criteria in the way of maximum number of exposures to impact sounds at different sound levels, as well as pulse length (the duration of the impact sound, measured in  milliseconds). The table below is a simplification of the military requirements, that does not take into consideration the pulse length. The table is therefore more conservative than the Military Standard.

-

Maximum permissible number of exposures per day

Impulse noise Limit No Protection Either Plugs or Muffs Both Plugs and Muffs
140 dB Unlimited Exposure Unlimited Exposure Unlimited Exposure
 160 dB 0 2,000 40,000
167 dB 0 100 2,000
173 dB 0 5 100


How do I select a hearing protector with adequate attenuation for my noise situation?

You need to know the approximate noise level of the environment you are seeking protection against. The decibel (dB) level can be measured with a sound level meter. This works fine in professional environments, but homeowners and consumers can use estimates and common sense. Most equipment and machinery used by homeowners, such as lawn mowers, chain saws, line trimmers and similar devices do not produce sounds in excess of 100dB. In addition the exposure time is usually limited to a couple of hours.

If you use a tool that produces 100 dB, and plan to use it for an hour or two, and you use an average hearing protector with a 25 dB Noise Reduction Rating, you will be more than adequately protected. Of course, if you also are exposed to noise at work, you must take this into consideration, since it is your total daily dose that matters. To calculate your exposure the EPA noise regulation advises that you deduct the NRR from the noise level.

  • Example, the tool and hearing protector discussed above: 100 dB – 25dB = 75 dB at the ear.
  • For professional applications, when the noise level is known in dB(A), OSHA advises that the NRR be reduced by 7 dB:
  • Example: 100dB(A) – (25 – 7)dB = 82dB at the ear.
  • OSHA may also require a 50% reduction of the NRR after the above reduction:
  • Example: 100dB – (25 – 7) x 0.5 = 91dB at the ear.

Read more about conflicting information from EPA, OSHA and NIOSH on how to use the Noise Reduction Rating.

What are the advantages of earmuffs over earplugs and vice versa?

Earmuffs are easier to use correctly, and therefore provide attenuation that is much closer to the laboratory derived NRR. Earplugs are hard or sometimes very hard to insert correctly, and therefore often do not provide the same attenuation in the field, as they do in the laboratory. This is the reason that NIOSH recommends different de-ratings for earplugs and earmuffs. You can read more about this subject by clicking on this link.

An earmuff may be preferable in the intermittent environment, while an earplug may be the choice in a long-term exposure. An earmuff may be preferred in a cold environment, while an earplug may be the choice in a hot and humid environment.

Most importantly, you should chose a protector that is comfortable and you should use it during the entire noise exposure.

What is the effect of dual protection? (Use of both earmuffs and earplugs).

This is a commonly asked question, and the answer is somewhat surprising. If you use an earmuff with 29 dB NRR and an earplug with 29 dB NRR, the estimated protection is 32 dB. The physical energy of noise doubles with every three decibels. This is a physical fact. So if you place two machines producing 90 dB of noise, next to each others, you will end up with a noise level of 93 dB. In the same manner if you double up protection you will gain 3 dB.

The above is an estimation, and both protectors have to be used correctly to achieve this result. We have actually seen laboratory reports indicating that as much as 6 dB can be gained from combined hearing protection. However, in real life situations, it is probably safe to assume 3 dB.

How is the attenuation for hearing protectors measured?

In order to establish the effectiveness of a hearing protector, the following method (with certain modifications) is used by all current standards. Ten subjects are exposed to sounds at 9 different frequencies (tones) and the lowest sound level that can be heard is established. The subjects are tested three times for each frequency, resulting in 27 individual sets of data. Thereafter each subject uses a hearing protector, and the procedure is repeated. The difference between the hearing threshold with and without hearing protector is the attenuation (noise reduction) achieved by a particular hearing protector. The average for all subjects become the mean attenuation, and the variance establishes the standard deviation. The example below shows the data compiled into a chart.

Frequency, Hz 125 250 500 1000 2000 3150 4000 6000 8000 H M L NRR
Mean Attenuation, dB

 22.1

27.9

34.9

35.8

37.3

41.4

42.3

41.6

41.2

37 33 27 29
Std. Deviation

 2.9

2.8

3.4

2.0

2.5

2.7

2.8

3.1

3.7


What does the NRR (Noise Reduction Rating) mean?

You can read an article about the NRR and other simplified methods at the following link.

www.elvex.com/facts03.htm

What factors, other than the noise level, combine to create a hearing damage?

Hearing damage can be created for many different reasons and sources. Industrial noise is certainly the most common and serious cause of hearing damage. Many leisure time activities also contribute, such as target shooting and hunting, noisy hobbies such as woodworking, as well playing in an orchestra or simply listening to music at excessive noise levels.

Another factor that contributes is heredity, and a certain level of hearing damage simply occurs from aging. Certain medications have also been demonstrated to contribute to hearing damage. As discussed above, exposure time is a major factor in determining the total daily noise dose.

Can I still hear the machinery and warning signals, when I use a hearing protector?

Extensive studies show that individuals with normal hearing, will hear warning signals slightly better when using a hearing protector. Individuals with an existing hearing damage will not hear the warning signals as well while using a hearing protector.

Can electronic hearing protectors help improve the ability to hear and communicate in a noisy environment?

Most likely you have heard about active headsets and noise canceling earmuffs. In theory the noise cancellation technology works by creating a negative sound wave for every noise (a series of sound waves), and thereby successfully cancel all noise for a perfectly quiet environment. Unfortunately this scenario is much more wishful thinking than reality. In order to be able to make the computations instantly, as we walk around in a changing noise environment, we would need a computer on a cart.

Today’s active or electronic headsets therefore are compromises that either are designed for specific noise environments, such as an airplane cockpit, or use some sort of filtering technique. The latter technique seeks to eliminate much more of the noise environment than of the speech, in order to improve the speech to noise relationship.

Electronic earmuffs can successfully eliminate impact noise, such as gunfire, and significantly contribute towards the ability to hear and communicate while on the shooting range or on a hunting team. This is done with an impact filter, which simply closes the electronics after sensing the sound wave from the noise impact. The filter reacts in microseconds and opens the electronics again after milliseconds (when the sound peak has passes).

Read about Elvex new DeTune electronic hearing protector.

Is it safe to listen to FM Radio earmuffs when you work?

OSHA has issued a letter of principal acceptance of this type of protection, on the condition that the noise level produced by the FM radio does not exceed 85 dB. Read the OSHA letter.

Who pays for my hearing protection at work?

OSHA has ruled that the employer pays for all necessary hearing protectors, including replacements. The employer decides what types of hearing protectors to offer, and has to make sure that they are adequate for the noise environment. The employer is required to offer a reasonable choice in order to maximize compliance. Read the OSHA Regulation….

How do I know if I have a hearing damage?

Your hearing threshold can be measured by an audiologist, and the instrument used to measure the hearing is called an audiometer. If you work in a noisy environment, and work for a larger company you have most likely already had your hearing tested.

What can I do if I already have an existing hearing damage?

Hearing damage is irreversible! If you already have a hearing damage, it becomes even more important that you make every effort to preserve your remaining hearing level. This means that you should avoid noisy environments whenever possible, and when you cannot avoid them, use an effective and comfortable hearing protector 100% of the exposure time.

If your hearing is already severely damaged, you should consult with an audiologist or specialist, in order to determine if a hearing aid may be able to improve your situation.

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FAQ Eye Protection

  1. What changes in the new ANSI Z87.1-2010?
  2. How strong are today’s safety glass lenses?
  3. What is a ballistic Vo rated safety glass?
  4. My safety glasses scratch easily. Do you have any solution?
  5. Do you offer safety glasses with anti-fog lenses?
  6. Do you have smaller sizes of safety glasses for women and children?
  7. Do you have safety glasses that can be adjusted for best possible fit?
  8. What is the purpose of the different color lenses?
  9. How do I select an appropriate eye protector?
  10. How do I get my workers to wear their safety glasses?
  11. What is the relationship between the diopter of a bifocal lens and magnification?
  12. Does OSHA approve safety glasses?
  13. How are safety glasses tested, and to what standards?
  14. How common are eye injuries?


How strong are today’s safety glass lenses?

Most safety glass lenses are today made from Polycarbonate, and this is a very tough material. The impact resistance of a Polycarbonate lens is approximately ten times higher that of a safety glass lens made from hardened glass. Both these lens types (has the potential to) meet the requirements of the Eye and Face Protection Standard, ANSI Z87. If you want to see an example of how tough a Polycarbonate lens is, click on this link: High impact, high velocity safety glasses.

What is a ballistic Vo rated safety glass?

Ballistic Vo rated is a test performed on a safety glass model to US Military standard MIL PRF-31013, clause 3.5.1.1, where the ballistic resistance of the spectacles shall be such that they will pass a Vo impact resistance test using a 0.15 caliber, 5.8 grain, T37 shaped projectile at a velocity of 640 to 660 feet per second. Note - this impact velocity requirement is 4 times the ANSI Z87 standard requirement of 150 feet per second. Click here for more information about ballistic Vo rating.

My safety glasses scratch easily. Do you have a solution?

Polycarbonate gains its strength from being flexible instead of rigid. Because of this Polycarbonate lenses are prone to scratching, and are therefore usually protected by a hard coating. Even with a hard coating Polycarbonate has to be handled carefully, and should cleaned with soap and water and dried with paper tissue. If your work environment is dusty and abrasive, you may want to consider safety glasses with hardened glass lenses, since they offer better scratch resistance than Polycarbonate lenses. Safety glasses with glass lenses are usually more expensive, and are not available in contemporary fashion styles. Elvex does not offer safety glasses with hardened glass lenses.

Do you offer safety glasses with anti-fog lenses?

Yes, Elvex offers different solutions to avoid fogging of safety glasses. Certain designs that provide a space between the face and the lens allow for air circulation and help minimize fogging problems. Examples: UniWraps, SG-20, Challenger, SG-25, Summit II, SG-29, Orbit, SG-36

We also offer several models with anti-fog coated lenses. The product number includes an AF designation after the regular product number. Examples: TNT (SG-13C-AF), Xenon, SG-14, Trix (SG-17C-AF), UniWraps (SG-20C-AF), Summit II (SG-29C-AF).

Click this link to go to our main safety glass page: Elvex main Safety Glass page.

Do you have smaller sizes of safety glasses for women and children?

Yes, we offer a couple of styles that are smaller or have a more aggressively curved lens. Elvex TTS, SG-15-small fit small featured adults as well as many children. There are several other models that fit female faces and small featured adults in general. Click on the link below for a summary.

Smaller safety glasses

Do you have safety glasses that can be adjusted for best possible fit?

Most of our models accommodate a wide range of facial features. Some models in our product line offers both angle and length adjustment of the temples. The angle adjustment allows the lens to be tilted so that it offers the best possible protection for the job at hand. This feature is also helpful for individuals with asymmetric faces (it is common that the right and left ears are at different heights). Models with both length and angle adjustment: UniWraps, SG-20 , Neutrom, SG-30, Bifocal Safety Glasses, RX-100.

Click this link to go to our main safety glass page: Elvex main Safety Glass page.

What is the purpose of the different color lenses?

Lenses are offered in different tints and coatings for a variety of reasons, such as vision enhancement, glare reduction and simply cosmetic appeal. Examples:

Lens type Performance Application
Amber-yellow Improves contrast, filters out blue light. Overcast conditions
Gray and Brown Glare reduction, works just like a sun glass. Approximately 80% of the visible light is filtered out. Sunny and bright conditions
Mirror coated Mirror coating is mostly a cosmetic aspect. However some mirror lenses filters out more light than a standard gray lens. Very bright conditions
Indoor/Outdoor This lens type is sometimes called a light mirror coating. It filters out about 50% of the visible light and is a compromise between a clear lens and a gray lens. Use in conditions where light conditions change from normal to bright
Light gray, Light brown These lenses offer properties similar to the Indoor/Outdoor lens, but w/o the glare, sometimes experienced with the I/O lens. Use when a standard gray lens is too dark for visual accuracy
Ice Blue Blue lenses provides more soothing light to keep worker’s eyes from getting tired. These lenses also filter 81% of blue light wavelengths and provide a reduction in visible light transmission. Softens harsh industrial lighting

You can read about the light filtration properties of all Elvex lenses, by clicking on this link:Light Transmission for Elvex Safety Lenses

How do I select an appropriate eye protector?

ANSI Z87.1 provides guidelines for what type of eye protection to use for different types of hazards. Here is some basic information:

  • If you use a face shield, it is strictly a face protector, and required eye protection has to be selected as appropriate.
  • If your work environment has impact hazards, use safety glasses that are appropriate for this type of hazard. Polycarbonate lenses are suggested. Make sure that glasses provide adequate coverage, so that there are no gaps in critical areas.
  • For chemical splash or mist, use only goggles that seal tightly against the face. For this environment make sure that the goggles have only indirect ventilation or no ventilation. As appropriate chose anti-fog coated lenses.
  • For injurious rays, such as welding or laser light, specialized safety glasses must be worn. Welding lenses must be marked with a SHADE designation, normally in the range of 2 – 5. Choose level of protection appropriate for the equipment that you use. Laser lenses must be selected uniquely for each laser�s characteristics, such as wavelength and power. Laser lenses must be marked with both wavelength and Optical Density (the protection factor).


How do I get my workers to wear their safety glasses?

Compliance with requirements to wear safety glasses used to be a big problem in industry. However, safety glasses have become much more lightweight and stylish, to the point where workers actually want to wear their safety glasses. If you offer a selection of stylish safety glasses, that are appropriate for your work environment, you will find that compliance is no longer a big problem.

What is the relationship between diopter and magnification?

Magnification =  1 + (Diopter / 4)

1.0 Diopter = 1.25 magnification (approx.)

1.5 Diopter = 1.375 magnification (approx.)

2.0 Diopter = 1.50 magnification (approx)

2.5 Diopter = 1.625 magnification (approx)

3.0 Diopter = 1.75 magnification (approx)


Does OSHA approve safety glasses?

No, OSHA does not approve safety glasses, or any other personal protective equipment for that matter. OSHA simply requires that manufacturers test their products to the appropriate ANSI standard. Read OSHA’s Eye and Face Protection Regulation, 29 CFR – 1910.133

How are safety glasses tested, and to what standards?

Safety glasses are required to be tested to ANSI Z87.1-2010. This standard includes optical requirements as well as physical requirement. Here is a list of the most important (not complete) tests that are required:

Test Performed Description
High Mass Impact Frame shall be capable of resisting impact from a pointed projectile weighing 500g (17.6 oz.) dropped from a height of 127 cm (50 in.).
High Velocity Impact Spectacles shall be capable of resisting impact from a 6.35 mm (1/4 in) diameter steel ball traveling at a velocity of 45.7 mps (150 fps).Goggles shall be capable of resisting impact from a 6.35 mm (1/4 in) diameter steel ball traveling at a velocity of 76.2 mps (250 fps).For sample size of 6, no failure may occur (Z87.1-2003 required 20).
Drop-Ball Impact Basic impact requirement for all devices: 1 inch diameter steel ball dropped at 127 cm (50 inches)
Coverage Required lateral (side) coverage has been increased, and it is now the same as CSA Z94.03-02. No openings greater that 1.5 mm (0.06″).
Penetration Test (Plastic lenses only) Spectacles shall be capable of resisting penetration from a weighted projectile weighing 44.2 g (1.56 oz dropped from a height of 127 cm (50 in).
Prismatic Power The prismatic power shall not exceed 1/2 prism diopter in any direction. Vertical and horizontal prism imbalance shall not exceed 1/4 prism diopter….
Refractive Power and Astigmatism The refractive power in any meridian shall not exceed 0.06 diopter. The astigmatism shall not exceed 0.06 diopter.
Haze Lenses shall not exhibit more than 3% haze, when tested in accordance with….
Optical Quality No striae, bubbles, waves or other visible defects that would impair optical quality is allowed.
Transmittance Clear and filter plano lenses shall comply with table 9 or 10 of Z87.1. Special purpose lenses shall comply with Table 7 through 10.
Cleanability After cleaning the function of the spectacles shall not be impaired.
Optional Tests There are optional tests for Welding lenses, UV lenses, IR lenses and VLT filters. For goggles optional tests include Splash/Droplet, Dust and Fine dust.
Markings Impact protector (must meet High mass Impact, High Velocity Impact and Penetration tests) shall be marked Z87+Non Impact Protector (must meet all requirements, except impact requirements) shall be marked Z87.Lens: Manufacturers mark, and if applicable “S” for lenses with less than 85% visible light transmission.Frame components: All major components shall bear Manufacturers mark and shall be marked “Z87″Optional tests and markings: There are optional tests for Welding lenses, UV lenses, IR lenses and VLT filters. If these properties are claimed, the have to be marked on the lens.

Welding: W-followed by shade number
UV filter: U and scale number
Visible light filter: L and scale number
IR filter: R and scale number
 
Goggles only:
Splash/Droplet: D3
Dust: D4
Fine Dust: D5


How common are eye injuries?

Every day an estimated 1,000 eye injuries occur in American workplaces. The financial cost of these injuries is enormous–more than $300 million per year in lost production time, medical expenses, and workers compensation. No dollar figure can adequately reflect the personal toll these accidents take on the injured workers.

The Occupational Safety and Health Administration (OSHA) and the 25 states and territories operating their own job safety and health programs are determined to help reduce eye injuries. In concert with efforts by concerned voluntary groups, OSHA has begun a nationwide information campaign to improve workplace eye protection.

Take a moment to think about possible eye hazards at your workplace. A 1980 survey by the Labor Department’s Bureau of Labor Statistics (BLS) of about 1,000 minor eye injuries reveals how and why many on-the-job accidents occur.

Read the full OSHA article at:

http://ehs.okstate.edu/training/oshaeye.htm

 

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