## Understanding Decibels & Why OSHA Pays Attention to Your Noise Exposure

In the simplest of metric terms, a decibel is one-tenth of a bel.  But, historically, bel was a unit created to honor Alexander Graham Bell who invented the telephone.  In the early days with telephone wires, they noticed that the signal strength would decay over a long distance.  In order to determine power requirements to connect people for communications, they determined that they could use the ratio of power levels.  As a start, it had to be based on a minimum amount of power required for a person to hear on the telephone.  They found that the signal power level to generate an angular frequency of 5000 radians per second would be that minimum value as determined by an average number of people.  They used this mark as a reference point in the ratio of power levels.  Because of the large variations in values, they simplified the equation on a base-10 log scale and dividing the bel unit by 10.  Thus, creating the measurement of decibel.

Today, this same method is used to measure sound.  Like frequency waves that travel through the telephone wires, pressure waves travel through the air as sound.  This sound pressure is what our ears can detect as loudness, and it has a pressure unit of Pascals (Pa).  As an example, a small sound pressure would be like a whisper while a large sound pressure would be like a jet engine.  This is very important to know as high sound pressures, or loudness, can permanently damage our ears.

With sound pressures, we can determine the Sound Pressure Level (SPL) which is measured in decibels (dB).  Similar to the equation for the telephone power signals above, the SPL also uses a ratio of sound pressures in a base-10 logarithmic scale.  For a minimum reference point, an average human can just start to hear a sound pressure at 0.00002 Pa.  So, the equation for measuring sound levels will use this minimum reference point as shown in Equation 1.

Equation 1:

L = 20 * Log10 (p/pref)

where:

L – Sound Pressure Level, dB

p – Sound pressure, Pa

pref – reference sound pressure, 0.00002 Pa

Why is this important to know the decibels?  OSHA created a chart in 29CFR-1910.95(a) that shows the different noise levels with exposure times.  This chart was created to protect the operators from hearing loss in work environments.  If the noise level exceeds the limit, then the operators will have to wear Personal Protection Equipment (PPE), or suffer hearing damage.  EXAIR offers a Sound Level Meter, model 9104, to measure sound levels in decibels.  It comes calibrated to accurately measure the sound to determine if you have a safe work environment.

There is a term that is used when it comes to loud noises, NIHL.  This stands for Noise Induced Hearing Loss.  Once hearing is damaged, it will not come back.  To keep your operators safe and reduce NIHL, EXAIR offers many different types of blow-off products that are designed to decrease noise to a safe level.  So, here’s to Alexander Graham Bell for creating the telephone which can be used to contact EXAIR if you have any questions.

John Ball
Application Engineer
Email: johnball@exair.com

Photo of Telephone by Alexas_FotosCC0 Create Commons

## Not All Compressed Air Guns Are The Same

If you work in an industrial plant or manufacturing environment, chances are you use some type of compressed air gun for cleaning parts, work areas, etc. Many air guns purchased through large industrial suppliers are a common choice due to the cost of the gun but as the saying goes – “you get what you pay for”. These types of guns may be cheap to purchase but they are also made cheap and have parts that can break easily, like the trigger or nozzle. In many cases, the nozzles on these guns are also in violation of OSHA requirements, producing dangerous discharge pressures and loud noise levels, which can lead to costly fines or potentially deadly injuries.

EXAIR offers 5 different styles of Safety Air Guns that not only eliminate these concerns, but also provide a more efficient operation, which can reduce energy costs. All of our Safety Air Guns are fitted with our engineered Air Nozzles  which meet OSHA Standard 1910.242(b) for 30 PSI dead end pressure, as they provide a relief or safe path for the air to exit if the nozzle were to be blocked or pressed against an operator’s body so the exiting air pressure will never reach 30 PSIG. They are also engineered to entrain surrounding air across the profile of the nozzle, which produces a smoother airflow, ultimately reducing wind shear, resulting in much lower sound levels, meeting OSHA Standard 29 CFR 1910.95(a).

The Precision Safety Air Gun body is made of a durable high impact, glass reinforced nylon, providing for a lightweight, ergonomic operation. These guns feature a curved extension, ideal for delivering a powerful stream of air in hard to reach areas, like clearing debris from drilled holes. All of the nozzles used with these units are either 316ss construction for durable, corrosion resistance or PEEK plastic for non-marring applications. The air inlet is 1/4 FNPT and there is a convenient hanger available for safe storage.

Our NEW VariBlast Compact Safety Air Guns are ideal for light to medium duty processes, featuring a variable flow trigger to achieve different force levels ranging from 2.0 ounces up to 1 pound, depending on the nozzle. The body is cast aluminum and there are (2) 1/4 FNPT air inlets available, 1 on the bottom and 1 on the back of the gun, as well as a storage hanger, for easy installation. Nozzles are available in zinc aluminum alloy, 303ss, 316ss and PEEK plastic. These guns are available with aluminum extensions from 6″ up to 72″.

The Soft Grip Safety Air Guns are commonly used in long-term use applications as they feature a comfortable grip and long trigger which helps to reduce hand and finger fatigue. The cast aluminum construction is well suited for more rugged environments and again, features a hanger hook. These guns can be fitted with aluminum, stainless steel or PEEK plastic to meet the demands of a variety of applications and are available with 6″ – 72″ aluminum extensions for extra reach or Flexible Stay Set Hoses , allowing the user to aim the airflow to a specific target area. The air inlets for these guns are going to be 1/4 FNPT.

EXAIR’s Heavy Duty Safety Air Guns deliver higher force and flows than other air guns, as these units feature a 3/8 FNPT air inlet, which maximizes the compressed air flow to the engineered Super Air Nozzle. Like the Soft Grip, the durable cast aluminum body is designed for use in tough industrial processes, and the ergonomic and comfortable trigger are ideal for hours of use. Aluminum extension are available, again in lengths from 6″ up to 72″, but feature a larger diameter for optimal flow and superior durability.

The Precision, VariBlast, Soft Grip and Heavy Duty Safety Air Guns are ALL available with an optional, polycarbonate Chip Shield to protect personnel from flying chips and debris, further meeting OSHA Standard 1910.242(b) for the safe use of compressed air.

Lastly we offer our Super Blast Safety Air Guns. The Super Blast Safety Air Guns are ideal for wide area blowoff, cooling or drying a part, as well as long distances. They feature a comfortable foam grip and spring loaded valve that will shut off the airflow if the gun is dropped. These units use our larger Super Air Nozzles and Super Air Nozzle Clusters, providing forces levels from 3.2 lbs. up to 23 lbs. Depending on which nozzle is fitted on the assembly, air inlets will range from 3/8 FNPT up to 1-1/4 FNPT. Aluminum extensions are available in 36″ or 72″ lengths.