The Definition of Arc-Rated (AR) Clothing

Definition of Arc-Rated (AR) Clothing

Arc-rated (AR) clothing is flame-resistant apparel that has been tested under ASTM F1959 to determine its arc rating, the incident energy, in calories per square centimeter (cal/cm²), the fabric can block before the wearer would likely receive the onset of a second-degree burn or the fabric breaks open. The rating is reported as an arc thermal performance value (ATPV) or an energy breakopen threshold (EBT). AR clothing is the foundation of arc flash PPE under NFPA 70E and is required by OSHA 1910.269 for employees exposed to electric arcs in power generation, transmission and distribution work.

Key Facts About Arc-Rated Clothing

• All arc-rated clothing is flame resistant, but not all flame-resistant clothing has an arc rating.
• ASTM F1506 is the performance specification for arc-rated garments worn by electrical workers.
• NFPA 70E PPE category minimum arc ratings: Category 1 is 4 cal/cm², Category 2 is 8, Category 3 is 25 and Category 4 is 40.
• About 1.2 cal/cm² is the incident energy associated with the onset of a second-degree burn, which defines the arc flash boundary.
• Layered systems must be tested as a system, because individual layer ratings can't simply be added together.
• Meltable synthetic fabrics such as polyester and nylon should not be worn under AR clothing.

Example of Arc-Rated Clothing

An arc flash label on a 480-volt switchboard lists an incident energy of 6.2 cal/cm². Before opening the cover for troubleshooting, the electrician puts on an 8 cal/cm² arc-rated shirt and pants over cotton underlayers, an arc-rated face shield and balaclava, voltage-rated gloves with leather protectors, and hearing protection.

How to Select and Care for AR Clothing

1. Check the arc flash label or risk assessment for the incident energy or PPE category.
2. Choose garments with an arc rating equal to or greater than the required level, covering the full body.
3. Wear clothing fastened and sleeves down, with natural-fiber or arc-rated underlayers.
4. Launder according to the manufacturer's instructions and avoid bleach and fabric softeners that can affect flame resistance.
5. Inspect before each use and retire garments that are torn, contaminated with flammables or worn thin.

Related Terms

• Arc Flash
• NFPA 70E
• Electrical Hazard
• Personal Protective Equipment (PPE)

Frequently Asked Questions: Arc-Rated Clothing

What is the difference between FR and AR clothing?

Flame-resistant (FR) clothing resists ignition and self-extinguishes, which protects against flash fire. Arc-rated (AR) clothing is FR clothing that has also been tested for protection against the intense heat of an electric arc and carries a cal/cm² rating.

Does the arc rating wash out?

Garments made from inherently flame-resistant fibers keep their properties for the life of the garment. Treated fabrics are designed to stay flame resistant through industrial laundering when cared for as directed. Contamination with oil, grease or flammable residues can reduce protection.

Can I wear a regular jacket over AR clothing?

Outer layers worn in an arc flash exposure must also be arc rated, since a non-rated jacket or rain gear can ignite or melt and defeat the protection underneath.