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Arc Flash PPE and Clothing – Requirements and Guidelines

Arc flash rated clothing and suits are made to reduce severity of injury in cases of arc flash explosions. An arc flash is a brief and intense event, where a large amount of current forms an electric arc between conductive surfaces. During the event, the surfaces between which the arc forms can rapidly (perhaps we can call it instantaneously) heat up to tens of thousands of degrees (can get to over 35,000F) causing rapid vaporization and drastic expansion of the metal, creating an actual explosive blast. In addition to the shockwave of the blast, the extremely hot gas also rapidly expands and heats objects in the vicinity, igniting flammable substances and burning surfaces.

Thus, in addition to exposing the surroundings to extreme heat for the (normally brief) time of its occurrence, an arc flash can also easily ignite clothing that isn’t made of special fire resistant materials. The burns that a person experiences as a result of an arc flash can become considerably more severe if the clothing that he wears continues to burn after the flash disappears – if the individual gets knocked out by the blast, who knows how soon somebody comes to aid and puts out the flame?

Clothing made of special arc flash fabrics is specifically made to not sustain combustion in addition to insulating some of the heat of the initial blast. Arc flash clothes are made in such a way that they stop burning very quickly as soon as the arc flash itself has passed – the materials self-extinguish.

Click here to shop arc flash clothing, specialized arc flash suits, or lineman gloves at Legion.

Now on to actual information on selecting the arc flash clothes for different HRC (Hazard/Risk Categories)… Here are some basic guidelines on how to select your arc flash rated clothes and PPE gear:

There are a total of 5 hazard risk categories for different intensity levels of potential flashes:

  • HRC 0 requires protective clothing made of non-melting or untreated natural fiber (such as untreated cotton, wool, rayon, silk, or blends of these materials) with fabric weight of at least 4.5 oz/yd2

  • HRC 1 requires arc rated clothing with minimum rating of 4 calories/cm2

  • HRC 2 requires clothing rated for 8 calories/cm2 or more

  • HRC 3 requires clothing rated for 25 calories/cm2 or more

  • HRC 4 requires clothing rated for 40 calories/cm2 or more

Normally, the higher the level – the more risk of serious injury. It is recommended to take every effort to de-energize equipment if the work requires protection level of 40 cal or more and only proceed with work (wearing proper arc flash PPE) if it is absolutely necessary to work with live equipment.

The heat energy that is created by the arc is measured in Calories, so the more potent the arc flash – the more Calories per centimeter squared of heat it will expose the victim to. Even small amounts of heat (a few calories/cm2) are fully capable of burning unprotected skin, so be careful to protect yourself properly if you are in an area that has potential to expose you to significant cal/cm2 levels. You probably wouldn’t hover your hands 1 inch above red-hot coals on a grill for over a second or two, and that would likely only expose you to a few calories/cm2 (depending on how serious your grill is, of course).

Below are some basics on garment selections and requirements for different Hazard Risk Categories of arc flash protective clothing:

HRC 0 Clothing and PPE

Protective clothing – made of non-melting or untreated natural fiber (i.e. untreated cotton, wool, rayon, or silk, or blends of these materials) with fabric weight of at least 4.5 oz/yd2:

  • Long sleeve shirt

  • Long pants

Protective equipment:

  • Safety glasses or safety goggles (required)

  • Hearing protection (ear canal inserts)

  • Heavy duty leather gloves (as required – see note 1 below)

HRC 1 Clothing and PPE

Arc-rated clothing with minimum arc rating of 4 cal/cm2 (see note 3 below):

  • Arc rated long sleeve shirt and pants or arc rated coverall

  • Arc-rated face shield (see note 2 below) or arc flash suit hood

  • Arc rated jacket, parka, rainwear or hard hat liner (as needed)

Protective equipment:

  • Hard hat

  • Safety glasses or safety goggles (required)

  • Hearing protection (ear canal inserts)

  • Heavy duty leather gloves (see note 1 below)

  • Leather work shoes (as needed)

HRC 2 Clothing and PPE

Arc-rated clothing with minimum arc rating of 8 cal/cm2 (see note 3 below):

  • Arc-rated long sleeve shirt and pants or arc-rated coverall

  • Arc-rated arc flash suit hood or arc-rated face shield (see note 2 below) and arc-rated balaclava

  • Arc rated jacket, parka, rainwear or hard hat liner (as needed)

Protective equipment:

  • Hard hat

  • Safety glasses or safety goggles (required)

  • Hearing protection (ear canal inserts)

  • Heavy duty leather gloves (see note 1 below)

  • Leather work shoes

HRC 3 Clothing and PPE

Arc-rated clothing selected so that the system arc rating meets the required minimum arc rating of 25 cal/cm2 (see note 3 below):

  • Arc-rated long sleeve shirt (as required)

  • Arc rated pants (as required)

  • Arc rated coverall (as required)

  • Arc rated arc flash suit jacket (as required)

  • Arc rated arc flash suit pants (as required)

  • Arc rated arc flash suit hood

  • Arc rated gloves (see note 1 below)

  • Arc rated jacket, parka, rainwear or hard hat liner (as needed)

Protective equipment:

  • Hard hat

  • Safety glasses or safety goggles (required)

  • Hearing protection (ear canal inserts)

  • Leather work shoes

HRC 4 Clothing and PPE

Arc-rated clothing selected so that the system arc rating meets the required minimum arc rating of 40 cal/cm2 (see note 3 below):

  • Arc-rated long sleeve shirt (as required)

  • Arc rated pants (as required)

  • Arc rated coverall (as required)

  • Arc rated arc flash suit jacket (as required)

  • Arc rated arc flash suit pants (as required)

  • Arc rated arc flash suit hood

  • Arc rated gloves (see note 1 below)

  • Arc rated jacket, parka, rainwear or hard hat liner (as needed)

Protective equipment:

  • Hard hat

  • Safety glasses or safety goggles (required)

  • Hearing protection (ear canal inserts)

  • Leather work shoes

Notes: (1) – if rubber insulating gloves with leather protectors are required by Table 130.7(C)(9), additional leather or arc-rated gloves are not required. The combination of rubber insulating gloves with leather protectors satisfies the arc flash protection requirements. (2) – Face shields are to have wrap- around guarding to protect not only the face but also the forehead, ears, and neck, or, alternatively, an arc-rated arc flash suit hood is required to be worn. (3) – Arc rating is defined in Article 100 and can be either the arc thermal performance value (ATPV) or energy to break open threshold (EBT). ATPV is defined in ASTM F 1959, Standard Test Method for Determining the Arc Thermal Performance Value of Materials for Clothing, as the incident energy on a material, or a multilayer system of materials, that results in a 50% probability that sufficient heat transfer through the tested specimen is predicted to cause the onset of a second-degree skin burn injury based on the Stroll curve, in cal/cm2. EBT is defined in ASTM F 1959 as the incident energy on a material or material system that results in a 50% probability of breakopen. Arc rating is reported as either ATPV or EBT, whichever is the lower value.

When dealing with arc flash hazards also keep in mind the potential for electric shock – when working with your hands around live wires, the possibility of electric shock is quite high, that is why most of the time arc flash suits and kits are supplied with rubber insulating gloves for shock protection instead of arc rated gloves for heat protection. Rubber insulating gloves should always be worn with proper leather protectors over them (leather protectors are to be shorter than the rubber gloves by 1″ of length for every 10,000 Volts that the wearer is exposed to).

The last thing that we will touch on is the Flash Protection Boundaries. Workplaces should have set boundaries for different hazard areas, and these boundaries depend on the farthest distance from an arc flash at which a person would receive a minor second degree burn – how close can an individual be to become at risk of injury in case of a sudden arc flash? Workers often walk by hazard sources without knowing about the danger if they aren’t properly marked. Trained safety professionals should investigate the hazards and determine the distances at which personnel may approach. In some applications, the hazards may be so abundant that it may be necessary to outfit all personnel with arc rated uniforms at the HRC 1 or 2 level to reduce risk, even if most workers do not actually deal with the electrical equipment, but simply have to be near it at times.

This article last updated on October 16, 2013.