Arc flash PPE categories and arc-rated clothing field guide

What arc flash PPE is, and where it sits

Arc flash PPE is the arc-rated clothing and equipment a worker wears to survive the heat and energy of an arc flash when the work has to be done energized. Arc-rated shirt and pants or a coverall, a face shield or a hood, arc-rated gloves over the right insulating gloves, and the head, eye, and hearing protection that goes with them. It is rated gear, tested to a number, not just heavy cotton that looks the part.

Where it sits in the plan is the part people get backwards. PPE is the last thing that protects you, after every effort to remove the hazard has failed or been ruled out. The work that should happen first is de-energizing the equipment and putting it in an electrically safe work condition through lockout/tagout, which is covered in its own guide. The arc-flash study and the label that comes out of it, covered in the arc flash study guide, are what tell you how much energy you are dressing for. PPE is what you reach for only when the gear cannot be turned off and proven dead.

So read this guide as the answer to one narrow question: the work is genuinely energized, it has been justified, and now the worker has to be protected. Everything here is about matching the clothing to the hazard and keeping it rated. None of it is a reason to work a circuit hot that could have been killed.

Why is PPE the last control, not the first?

PPE is last because it does nothing to prevent the arc. It only limits the injury if the arc goes off with a worker standing in front of it. NFPA 70E builds the whole approach around the hierarchy of controls, and the order runs from most effective to least: eliminate the hazard, substitute a safer method, engineering controls, awareness and administrative controls, then PPE at the bottom. The clothing is the bottom of that list on purpose.

Eliminate means de-energize. A dead, locked, tagged, and verified circuit cannot arc, so the worker needs no arc-rated clothing to be safe from it. That is the win, and it is why NFPA 70E requires equipment over a threshold voltage, commonly 50 V, to be put in an electrically safe work condition before work begins unless energized work is justified. Engineering controls reduce the energy or move the worker back: remote racking, arc-energy-reduction settings, remote operators on a breaker so nobody stands at the door.

The reason the order matters on the job is that crews skip to the bottom. They suit up in a 40 cal hood and treat the suit as permission to open a panel that could have been shut down over a lunch break. The suit is the worst protection in the stack, not the best, because it accepts that the arc happens and only tries to keep you alive through it. Reach for it last, and only when the steps above it genuinely cannot be done.

What does an arc flash do to a worker?

An arc flash is a short circuit through the air, and what it does to a worker is burn, blast, and deafen, all in a fraction of a second. The arc itself runs at temperatures several times hotter than the surface of the sun, hot enough to vaporize copper and melt steel. The heat is what the arc-rated clothing is fighting. A bare cotton or synthetic shirt does not stand a chance against it, and bare skin takes a deep burn from energy levels that sound trivial on paper.

The heat is only part of it. The arc flashes copper to vapor and the vapor expands hundreds of times in volume, which is the arc blast: a pressure wave that throws a worker off a ladder, ruptures eardrums, and turns loose hardware and panel parts into shrapnel. The sound peaks loud enough to cause permanent hearing loss on its own. Molten metal sprays out and ignites ordinary clothing, which then keeps burning against the skin after the arc is gone.

That last point is why arc-rated clothing matters as much as the cal number. A regular work shirt does not just fail to protect, it catches fire and adds a second burn source. The job of the PPE is to take the thermal hit without igniting, without breaking open, and without melting onto the worker. Everything else in the system is built around that one survival requirement.

Incident energy, and matching the arc rating to it

Incident energy is the amount of thermal energy a worker would receive at a normal working distance if the arc went off, expressed in calories per square centimeter (cal/cm2). It is the hazard number. The arc rating of the clothing is the protection number, in the same units. The rule is simple and it is the whole point of this guide: the arc rating of the PPE has to be at or above the incident energy the worker could be exposed to.

Where the incident energy comes from is the arc-flash study, and it lands on the label bolted to the gear. The study calculates the energy at each piece of equipment and the label prints it, so the worker is not guessing. If the label says 8.2 cal/cm2 at the working distance, the clothing system has to be rated for at least 8.2, and in practice you pick gear with a rating comfortably above it, not exactly on it. The arc flash study and labels guide covers how that number is produced.

At or above is not a suggestion. PPE rated below the incident energy is the single most dangerous mistake in this whole subject, because it looks like protection and is not. A 12 cal suit on a 25 cal bus is a worker who is dressed and exposed at the same time. Read the number, then beat it.

What are the two ways to select arc flash PPE?

NFPA 70E gives two methods to select arc-flash PPE, and the central rule is that you use one or the other on a given piece of equipment, never both blended together. The first is the incident energy analysis method: an engineering study calculates the cal/cm2 at each bus, and you pick PPE with an arc rating at or above that calculated value. The second is the arc flash PPE category method: a set of tables in the standard that assign a PPE category based on the equipment type, voltage, available fault current, and clearing time, used where no incident energy study exists.

The two live in different parts of the standard. The incident energy analysis path and the category-table path are each spelled out in NFPA 70E article 130, with the category tables long carried under 130.7, and the selection rules under 130.5. Section numbers move between editions, so confirm them against the edition the site has adopted before citing a clause. The principle does not move: pick a method, then stay in it.

The mistake that gets written into programs is mixing them. You cannot take a calculated incident energy number and use it to look up a PPE category from the table, and you cannot take a category and pretend it is a measured cal value for a different task. If you have a study, you select to the cal number. If you do not, you use the category tables within their stated limits. Crossing the streams produces a selection that is defensible under neither method.

What are the arc flash PPE categories?

The arc flash PPE categories are four levels, 1 through 4, each tied to a minimum arc rating for the clothing system. They belong to the category-table method, the one you use when there is no incident energy study. The number is not a cal value off a label. It is a tier that bundles the required clothing and equipment together so a crew working from the tables knows what to wear without an engineer running the math.

The minimum arc ratings hold steady across recent editions: Category 1 is a minimum of 4 cal/cm2, Category 2 is 8, Category 3 is 25, and Category 4 is 40. Each step up adds protection and adds layers. Category 1 and 2 are an arc-rated shirt and pants or a coverall with a face shield or hood. Category 3 and 4 step up to a full arc flash suit with a hood. Confirm the exact required items against the adopted edition's table, because the clothing list per category is part of the standard, not folklore.

One hard limit sits above Category 4. Where the hazard runs past 40 cal/cm2, NFPA 70E does not treat that as a higher category to dress for. It is a stop. Energy at that level is treated as too dangerous to work energized, so the answer is to de-energize, not to find a bigger suit. A category is a clothing tier, never a license to stand in front of energy nobody should be standing in front of.

The arc rating: ATPV and EBT

The arc rating is the cal/cm2 a garment or fabric protects to, and it is reported one of two ways: ATPV or EBT. ATPV, the arc thermal performance value, is the incident energy at which enough heat passes through the fabric to give the wearer a second-degree burn, judged against the Stoll curve. EBT, the energy breakopen threshold, is the energy at which the fabric breaks open and lets the arc through. A material gets whichever value it reaches first, and that single number is its arc rating.

Both are real ratings and both are determined by the same test method, ASTM F1959. You do not pick between them as a buyer. The fabric earns one or the other depending on whether it fails by letting heat through or by breaking open. A garment labeled 12 cal ATPV and a garment labeled 12 cal EBT both protect to 12 cal/cm2 for selection purposes. What you compare against the hazard is the arc rating, by whichever method it was earned.

The number on the tag is the number you select to. A garment with an 8 cal arc rating is a Category 2 garment by the rating, and it covers an 8 cal hazard, not a 10 cal one. When you build a layered system, the system has its own tested arc rating, which is what counts, not the sum you might guess from the individual pieces.

What is the difference between arc rated and FR clothing?

Arc-rated and flame-resistant are related but not the same, and the difference can decide whether a worker is protected. FR, flame-resistant, means the fabric resists igniting and self-extinguishes when the flame source is removed. AR, arc-rated, means the fabric is FR and has also been tested and assigned an arc rating in cal/cm2 for an electric arc. Every arc-rated garment is flame-resistant. Not every flame-resistant garment is arc-rated.

That asymmetry is where the field mistake lives. A shirt can be genuinely FR, sold for flash fire or welding work, and carry no arc rating at all. Put it on an arc-flash job and you have a garment that will not ignite but has no tested number to compare against the hazard on the label. For electrical arc work you need the arc rating, which means the garment has to meet ASTM F1506, the specification for arc-rated apparel for electrical workers, and carry a cal/cm2 value.

So the check is short. For arc-flash protection, the tag has to show an arc rating in cal/cm2 and reference the AR clothing standard. FR alone, with no cal number, is not arc-flash PPE no matter how flame-resistant it is. If the tag has no arc rating, the garment does not get used to satisfy an arc-flash hazard.

The arc-rated clothing system

Arc-rated clothing is a system, not a single garment, and the rating that matters is the rating of the system as worn. For lower hazards in the Category 1 to 2 range, the system is an arc-rated long-sleeve shirt and arc-rated pants, or a single arc-rated coverall, with the sleeves down and the front closed. Open the cuffs or leave the front gaping and you have undone the rating at exactly the gaps where an arc finds skin.

For higher hazards in the Category 3 to 4 range, the system is a full arc flash suit: an arc-rated coat and bib or coverall plus an arc flash hood, worn over arc-rated base layers. The suit is bulky and hot, which is part of why de-energizing is always the better answer when it is possible. Coverage has to be complete. An arc flash suit with a wrist gap, an open collar, or a missing hood is rated on the tag and unrated on the body.

Match every piece to the same hazard. A 40 cal coat with a 12 cal hood is a 12 cal system at the head, which is where you least want the weak point. The worker is protected to the lowest-rated piece in the line of fire, so the head, face, hands, and torso all have to clear the number, not just the jacket.

Layering and the layer that melts

Layering raises the protection, but only if it is done right, and one rule under it is not negotiable: nothing meltable goes next to the skin. Arc-rated layers can be combined, and a tested multi-layer system carries an arc rating higher than its individual pieces because the air gaps and added fabric slow the heat. That is the legitimate way to reach Category 3 and 4 ratings, with an arc-rated base layer under an arc-rated suit.

The killer is the underlayer. Polyester, nylon, acetate, and the usual synthetic t-shirt or base layer melt under arc heat, and molten synthetic against skin causes a burn far worse than the arc alone, because it sticks and keeps burning. NFPA 70E prohibits meltable synthetics as the layer next to the skin under arc-rated clothing for exactly this reason. The base layer must be arc-rated or an untreated natural fiber such as cotton, wool, or silk that chars instead of melting.

Check it before the suit goes on, every time. The arc-rated suit does its job and the worker still takes a melt burn from the moisture-wicking shirt nobody checked underneath. That synthetic gym shirt is the one rookies wear under the suit because it is comfortable, and it is the one that does the damage. Cotton or arc-rated, against the skin, no exceptions.

Head, face, and the hood

The head and face take their own arc-rated protection, and the level steps with the category. A hard hat protects against impact and falling parts, but it is not arc-rated by itself, so the arc protection comes from what goes with it. In the Category 2 range that is an arc-rated face shield plus an arc-rated balaclava, the sock-style hood that covers the parts of the head and neck the face shield leaves open.

At Category 3 and 4 the face shield and balaclava are not enough, and the system uses a full arc flash hood. The hood wraps the entire head with an arc-rated window, sealing the gaps that a flat face shield cannot cover. The window and the hood carry their own arc rating, which has to clear the same hazard as the rest of the suit. A hood rated below the body of the suit is the weak point sitting over the most exposed part of the worker.

Eyes get protected under all of it. Safety glasses or goggles stay on under the face shield or hood, because the shield can be lifted and the arc does not wait for it to be down. Hearing protection belongs here too, since the arc blast is loud enough to cause permanent loss, and the hood does not stop the sound.

What is the difference between shock and arc flash PPE?

Shock PPE and arc-flash PPE protect against two different hazards, and a worker on energized gear usually needs both at once. Shock is contact: current passing through the body. Arc flash is thermal: the heat and blast of a fault arcing through the air nearby. The protection for each is a separate set of equipment, selected separately, and one does not cover for the other.

Shock protection is rubber insulating gloves rated for the voltage, insulated tools, and the approach boundaries that keep a worker far enough from energized parts. Arc-flash protection is the arc-rated clothing, the hood or face shield, and the arc-flash boundary. A worker racking a breaker hot needs the arc-rated suit for the flash and the rubber gloves for the shock, because both hazards are live at the same time and the suit does nothing to stop current through the hands.

This is where gear gets confused on the job. Rubber insulating gloves are shock protection, not arc protection, and arc-rated gloves are arc protection, not a substitute for the rubber. They are often worn together: rubber insulating gloves for the voltage, leather protectors over them for mechanical damage, and the combination handles both the shock and a degree of arc. Sort the hazard first, then the PPE for it. Mixing the two is how a worker ends up protected against the wrong thing.

Rubber insulating gloves for shock

Rubber insulating gloves are the primary protection against shock when hands work near or on energized conductors, and they are rated by voltage class, not by cal/cm2. The classes run 00, 0, 1, 2, 3, and 4, from the lowest voltage up to the highest, and each class has a maximum AC use voltage you do not exceed. Pick the class for the voltage you are working, and confirm it against the specification rather than the color or the box.

Rubber gloves do not get worn bare. A leather protector goes over the rubber to take the abrasion, the puncture, and the snag that would otherwise breach the insulating rubber, since a pinhole in the rubber is a path for current the worker cannot see. The rubber insulates, the leather guards the rubber. Many arc-rated work systems wear this pairing as the hand protection, and on higher arc hazards arc-rated overgloves or heavier protectors are added so the hand clears the thermal number too.

Treat the rubber as the life-safety item it is. A class 0 glove covers up to its rated voltage and no more, and using a class below the working voltage is the same category of error as a suit below the incident energy. The voltage decides the class. Never the other way around.

Glove classes, testing, and the field air test

Rubber insulating gloves are only protective if they are tested and in date, and the rubber degrades whether you use it or not. Under the in-service care specification, ASTM F496 (paired with OSHA 1910.137), gloves are electrically tested on a fixed interval, and the in-service rule commonly cited gives six months from the issue date before the glove has to be retested. A glove past its test date is treated as failed until it is retested, no matter how good it looks.

The retest is a lab dielectric test, not something done in the truck. Gloves go out for the periodic electrical test, come back stamped with a date, and that date is what you check before you put them on. Track the issue date and the test date, because the calendar is what disqualifies a glove long before any visible damage does.

Before each use, the worker does an air test on the spot. Roll or twist the glove to trap air inside, then press and watch for the cuff to swell and hold, and listen and feel for a leak. A glove that loses air has a hole, and a hole is a shock path. The air test catches the puncture the leather protector was supposed to prevent and did not. It takes seconds and it is done every time, not once a day.

Feet, hearing, and the rest of the kit

The clothing and gloves carry most of the load, but the kit does not stop there. Footwear matters: leather work boots resist the heat better than synthetic, and electrical-hazard rated footwear adds a layer of shock protection by resisting current through the foot to ground. The footwear is a backup to the primary methods, not a substitute for de-energizing or for the rubber gloves, but it belongs in the system.

Hearing protection earns its place because of the blast. An arc is loud enough to cause permanent hearing loss in the instant it goes off, and the arc flash hood does not seal the sound out. Earplugs or muffs under the hood are part of arc-flash PPE for higher-energy work, not an optional add. Hands also get attention beyond the rubber and leather, with arc-rated gloves where the thermal hazard at the hand calls for it.

The rest is what completes coverage. No exposed skin in the line of fire, sleeves down, collar closed, nothing meltable showing. The system protects to its gaps, so the kit is built to close them.

The arc flash and shock boundaries

Boundaries are the distances that tell a worker when PPE is required and how close anyone can get, and there are two kinds because there are two hazards. The arc-flash boundary is the distance from the gear at which the incident energy falls to 1.2 cal/cm2, the level generally tied to the onset of a second-degree burn on bare skin. Inside that boundary, arc-rated PPE is required. The study calculates it and the label prints it.

The shock approach boundaries are separate and are about contact, not heat. They set how close an unqualified person may come and how close a qualified person may come to exposed energized parts, scaling with voltage. They are not the same line as the arc-flash boundary and can fall inside or outside it depending on the gear. The arc flash study and labels guide covers how both are derived and what the label has to show.

Carry the boundaries as the trigger for the PPE, not as trivia. Crossing the arc-flash boundary on energized gear is the moment the arc-rated clothing has to be on and rated. Crossing a shock boundary is the moment the rubber gloves and the rest of the shock protection have to be in place.

Insulated tools for energized work

Insulated tools are part of the shock protection on energized work, and they are not the same as ordinary tools with a coated handle. A true insulated tool is rated and tested to a voltage, commonly marked for 1000 V on the kind of low-voltage work where energized tasks happen, and the insulation is built into the tool, not a comfort grip. The marking and the rating are what make it protective.

The point of the insulated tool is to remove one more shock path. A screwdriver that slips across two terminals is both a shock hazard and an arc source, and an insulated tool reduces the chance that a slip turns into a fault. Inspect them like the gloves: a nick or a crack in the insulation is a failed tool, because the bare metal under the breach is a path for current.

Insulated tools support the gloves and boundaries. They do not replace them, and they are no reason to work a circuit hot that could have been killed first.

What cal rating PPE do I need?

The cal rating you need comes off the arc-flash label, and the rule is to pick PPE with an arc rating at or above the incident energy printed there. Read the label on the specific piece of gear you are about to work. It carries the incident energy in cal/cm2 at the working distance, the arc-flash boundary, the shock approach boundaries, and often the required PPE. The number on that label is the hazard you are dressing for, for that task, at that gear.

Then select up. If the label reads 9.5 cal/cm2, you do not put on a 9.5 cal garment and call it matched. You select a system rated comfortably above it, because the rating is a threshold for the onset of a burn, not a guarantee of no injury, and field conditions are never the lab. A worker dressed exactly at the number has no margin for a slightly worse arc than the model assumed.

If there is no label and no study, you are in the category-table method, and you select the category from the tables using the equipment and system limits they specify, staying inside their stated conditions. What you never do is read a cal number off a label and then go pick a category from the table as if they were interchangeable. Label and study means select to the cal value. No study means the category tables, within their limits. The arc flash study and labels guide is where the label itself comes from.

The energized work permit and the qualified person

Energized work is the exception, and NFPA 70E gates it behind a written permit and a qualified worker. The energized electrical work permit documents why the equipment cannot be de-energized, what the hazard is, and what protection is in place, and it is required when work happens on or near exposed energized parts that are not in an electrically safe work condition. The narrow justifications are that de-energizing would create a greater hazard or is genuinely infeasible, not that it is inconvenient or slow.

The permit is not paperwork for its own sake. It forces the crew to name the incident energy, the boundaries, the PPE, and the reason the work is hot before anyone opens the gear, which is exactly the moment those decisions should be made. The lockout/tagout guide covers the electrically safe work condition the permit exists to avoid, and the permit is the admission that the safe condition is not being reached this time.

Only a qualified person does this work. Qualified means trained on the construction and operation of the equipment, trained to recognize and avoid the hazards, and trained in the PPE and procedures, with that training current. PPE on an untrained worker is a costume. The training is what makes the gear protective, because it is what keeps the worker out of the situations the gear cannot save them from.

Energized PPE on critical-power and data center work

Critical-power sites raise the stakes on this whole subject, because the pressure to work energized is highest where the load cannot go down. A data center, a hospital, a trading floor, all run gear that owners are reluctant to de-energize, and that reluctance is exactly where energized work and its PPE get over-relied on. The right answer is still to design and operate so the gear can be safely de-energized, through redundancy and concurrent maintainability, not to treat the arc suit as the standing plan.

Where energized work genuinely cannot be avoided on these sites, the same rules apply with no discount. The label drives the PPE, the permit justifies the work, and arc-energy-reduction methods on the gear are worth the engineering because they lower the incident energy a worker faces. Lower energy means lower-category PPE, more tasks done at all, and a smaller blast if it ever goes off. On critical-power gear, reducing the hazard at the source pays back every time.

The trap is normalizing hot work because the site never goes dark. A facility that works everything energized because shutting down is hard has not solved the hazard. It has decided to wear it.

Caring for arc-rated clothing so it stays rated

Arc-rated clothing keeps its rating only if it is cared for the way the maker specifies, and a few laundry habits will quietly kill the rating without changing how the garment looks. Do not use chlorine bleach, and do not use fabric softener. Bleach can degrade the arc-rated fibers, and fabric softener leaves a flammable residue that can ignite, which is the opposite of what the garment is for. Wash to the manufacturer's instructions, and keep industrial laundering to a provider that handles arc-rated apparel.

Contamination is the other rating-killer. Arc-rated fabric that is soaked in grease, oil, solvents, or other flammable material can ignite and burn even though the base fabric is flame-resistant, because the contaminant burns. A garment that cannot be cleaned of a flammable contaminant is done, regardless of its age. The same goes for any field modification: cutting, adding non-rated patches, or sewing on non-rated trim breaks the tested system and voids the rating.

Treat the garment as a piece of safety equipment, not a uniform. The rating lives in the fabric and its condition, and a 25 cal suit caked in hydraulic oil is not a 25 cal suit anymore. Keep it clean, keep it unmodified, and follow the tag.

Inspection and replacement

Arc-rated clothing and the rest of the PPE get inspected before use, and the items that fail get pulled, not patched. Look the clothing over for holes, worn or thin spots, tears, frayed seams, broken closures, and contamination, because any of those breaks the protection at the spot it appears. A hole in an arc-rated sleeve is a hole the arc goes through, and a closure that will not seal is a gap that stays open.

Damaged or contaminated arc-rated clothing comes out of service. There is no field repair that restores a tested rating, so a garment with a hole, a burn, or a flammable contamination that will not wash out is replaced. The face shield and hood window get the same look for cracks, crazing, and scratches that obscure vision or weaken the window. A hood you cannot see clearly through is a hazard of its own at the moment the worker most needs to see.

Rubber gloves carry their own retest cycle on top of the visual check, with the periodic dielectric test and the before-use air test described earlier. The pattern across all of it is the same: inspect every time, trust the date and the damage over how the gear looks, and replace rather than gamble. The whole point of the PPE is the day the arc goes off, and that is not the day to find the hole.

Field checklist

Common mistakes

• Wearing PPE with an arc rating below the incident energy on the label, which looks like protection and is not.
• Putting a meltable synthetic shirt next to the skin under arc-rated clothing, which melts into a worse burn.
• Reading a cal value off a label and using it to pick a PPE category from the table, mixing the two methods.
• Treating rubber insulating gloves as arc protection, or arc-rated gloves as shock protection, instead of using each for its hazard.
• Working with rubber gloves that are past their test date or have failed the air test.
• Reaching for the arc suit first instead of de-energizing gear that could have been shut down and locked out.
• Wearing a high-rated suit with a lower-rated hood or face shield, leaving the head as the weak point.
• Keeping a contaminated or holed arc-rated garment in service, or laundering it with bleach or fabric softener.

Standards and references

NFPA 70E, the standard for electrical safety in the workplace, is where the PPE rules live. It sets the hierarchy of controls that puts PPE last, the two selection methods, the arc flash PPE categories and their minimum arc ratings, the boundaries, and the energized electrical work permit. The incident energy and category-table selection paths sit in article 130, with the category tables long carried under 130.7 and the selection requirements under 130.5. Section numbers and table designations shift between editions, so confirm them against the edition the jurisdiction or the site has adopted before citing a clause.

The clothing and the test methods come from ASTM. ASTM F1506 is the performance specification for arc-rated apparel for electrical workers, the standard a garment meets to be sold as arc-rated. ASTM F1959 is the test method that determines the arc rating, the ATPV or EBT value, of a fabric or system. For shock PPE, ASTM D120 is the specification for rubber insulating gloves and their voltage classes, ASTM F496 covers in-service care and the periodic electrical test, and ASTM F696 covers the leather protectors.

OSHA makes the duty enforceable. The general-industry electrical-safety rules in 29 CFR 1910 Subpart S and the electrical protective equipment requirements in 1910.137 are the law behind the practice, and OSHA recognizes NFPA 70E as a way to meet that duty. Above all of it, the incident energy on the label and the manufacturer's instructions on the garment control the specific selection. Match the arc rating to the hazard, never put a meltable layer next to the skin, and de-energize first whenever the work allows it.

Units, terms, and conversions

Arc-flash and shock PPE carry a small vocabulary that shows up across labels, tags, and specs, and the same idea sometimes wears two names.

Incident energy and arc rating are both in calories per square centimeter (cal/cm2). The arc rating is also written as ATPV or EBT depending on how the fabric was tested, and both are the cal/cm2 the garment protects to. Arc-rated is abbreviated AR and flame-resistant is FR, and AR is the subset of FR that carries an arc rating. Rubber insulating gloves are graded by voltage class, 00 through 4, by maximum use voltage, not by cal/cm2. The arc-flash boundary is a distance, the line where incident energy reaches 1.2 cal/cm2.

Incident energy

Thermal energy a worker would receive at the working distance from an arc, in cal/cm2

Arc rating (ATPV / EBT)

The cal/cm2 a garment or system protects to, by arc thermal performance value or energy breakopen threshold

AR vs FR

Arc-rated is flame-resistant fabric that also carries a tested arc rating; all AR is FR, not all FR is AR

PPE category

A table-method tier, 1 to 4, each with a minimum arc rating of 4, 8, 25, and 40 cal/cm2

Voltage class (gloves)

Rubber insulating glove rating, class 00 to 4, by maximum use voltage, for shock not arc

Arc-flash boundary

Distance from the gear where incident energy falls to 1.2 cal/cm2, the burn-onset threshold

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