Flame Resistant (FR) and Arc rated (AR) Clothing

Flame Resistant (FR) and Arc rated (AR) Clothing, these 2 terminologies are very often being heard about in the PPE industry today. As per NFPA70E, what was earlier referred to as Flame resistant (FR) clothing is now called Arc Rated (AR) clothing.

A simple note defines the difference between these 2 terms – ALL clothing with an Arc rating (AR) is Flame Resistant (FR), but not all FR clothing has an Arc rating. AR clothing are designed to protect the wearer against Arc Flash. The level of the AR clothing is defined by how much heat energy the fabric is able to block.

Flame resistant clothing is known to provide two-fold protection:

• Against Flame:

FR clothing is worn to guard against flame during an accidental fire situation. Protective clothing is put through Flame Test, as per various standards like ISO 15025, ASTM D6413 etc. to determine the protection level of material under controlled conditions.

• Insulates the wearer against heat hazards:

Insulation against heat hazards is the second function of FR clothing. Flame resistant clothing provides the wearer protection from various heat related hazards like radiant heat, convective heat, contact heat etc. and can lessen the impact on the area directly affected by the accident.

To be an Arc rated (AR) fabric, it must first be a FR fabric. Depending upon the weave construction, blend and weight of the fabric, it may offer different levels of arc protection.

According to the various arc rating standards like ASTM F1959, IEC / EN 61482-1-1 clothing needs to be FR before it can even be tested to determine its Arc rating.

How an Arc Rated fabric (AR) is tested?

For the ASTM F1959, IEC / EN 61482-1-1 testing, 21 samples of textile material are subjected to an arc flash and heat transfer is measured through the fabric using sensors. Stoll curve model predicts whether or not a 2nd degree burn would result by use of the textile material and also calculates the energy likely to cause the onset of 2nd degree burns through the fabric, 50% of the times the material is tested. This energy level determines the Arc rating of the textile material. This energy is expressed in calories per centimeter square (cal/cm²). The arc rating can be reported as ATPV (Arc Thermal Performance Value) or EBT (Energy Breakopen Threshold). ATPV and EBT may both be evaluated in the same test, but the first point to be reached is reported as the arc rating.

Why one size of PPE does not fit all

Personal protective equipment (PPE), such as arc rated FR clothing, is a critically important part of every electrical safety program. It should be used as the last line of defense, meaning it helps protect when all other preventative measures have failed. In fact, the hierarchy of controls puts eliminating the hazard as the most effective way to protect workers. However, in many cases engineering can reduce but not eliminate the hazard. Energized work poses an arc flash risk, and there’s really no such thing as a “small” arc if you are the person standing in front of it. Virtually all arcs pose an ignition risk to flammable clothing.

Since FR clothing is not meant to be used as a primary protection method, it’s fallacy to believe that one size of PPE fits all types of employees. A successful safety program will address each situation independently and treat individuals in the safety program uniquely depending on their job function and exposure to a hazard. Being safe is just as much about the employees themselves and employees buying in to the program to make safety a priority and not something their company tells them they have to think about.

If it’s determined that PPE is needed, companies need to address what type of PPE is best and offers the most protection. For electricians, choosing rubber gloves and PPE based on the proper size and voltage ratings can prevent accidents by permitting the worker the proper dexterity needed to perform electrical tasks.

To make a program easy and more manageable, some companies may only want to buy XL PPE. However, this fails to recognize that workers come in many shapes and sizes. For example, if sleeves are too long, electricians may roll their sleeves up and expose his or her wrists and hands to injury. Sleeves need to be worn buttoned and tight-fitting on the arm.

Likewise, wearing garments that are either underrated or too bulky can put electricians in harm’s way. Many safety managers say they need PPE Category 2 protection but this level of protection is rather broad. Wearing minimum PPE Category 2 apparel when the incident energies can exceed 20 or 30 cal/cm2 could cause severe third degree burns that may lead to infection or death, if the electrician survives the initial incident. At the other extreme, using a PPE Category 4 suit and hood when a PPE Category 2 is recommended could make movement and visibility unnecessarily difficult for the electrician. This may end up creating a dangerous situation rather than protecting against one.

Clearly, the one-size-fits-all approach is not appropriate for workers needing PPE. Choosing garments that are the right sizes for each worker ensures that protective clothing is worn properly and will provide the optimum amount of safety.

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