What's The Difference Between Arc-rated and Flame-resistant?

What's The Difference Between Arc-rated and Flame-resistant?
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What's The Difference Between Arc-rated and Flame-resistant?

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Arc-rated and flame-resistant seem like they might be the same thing. These two different standards are often confused. To sum it up, all Arc-Rated PPE is flame-resistant, but flame-resistant PPE is not Arc-Rated. If you don't get it yet, you will soon enough.

FLAME RESISTANT

Flame-Resistant PPE should be worn while doing any electrical work that requires no Arc-Rated PPE. What that means is, if the threat of electrical hazard is low, the worker can wear Flame-Resistant PPE.
How is "low" measured? The chance of electrical hazard is measured by an analysis that yields an "incident energy level," which uses the unit cal/cm2 (calories per square centimeter). That’s a unit you’re going to be seeing a lot of, sometimes just called “cal" or "calories."
If the incident energy level of a job is under 1.2cal/cm2, it is safe to wear Flame-Resistant PPE. The number 1.2cal/cm2 is the threshold for a second-degree burn. That means if an electrical hazard could result in anything more severe than a first-degree burn, Flame-resistant PPE is not enough. You’ll see incident reading under 1.2cal/cm2 while conducting routine tasks, such as operating a circuit breaker, inspecting stable equipment, or using thermal imaging outside the flash boundary of equipment.
Another way to look at it is, if you are working on anything that is 50V or higher, you need to wearing Arc-Rated gear, not just Flame-Resistant.
Flame-Resistant PPE provides a couple of types of protection to the wearer. In an electrical hazard, the Flame-Resistant material prevents ignition compared to Non-Flame-Resistant material. In the event of an electrical hazard with exposed skin, the worker WILL be burned at the contact point. The Flame-Resistant clothing WILL NOT ignite, preventing the wearer from also being scorched by their clothing.
Depending on the circumstances of an incident, the Flame-Resistant material may also insulate the wearer from a higher degree burn. A hazard that would typically result in a second-degree burn on bare skin would be less severe with Flame-Resistant PPE.
Most Flame-Resistant PPE has a maximum number of wash cycles before being not considered Flame-Resistant anymore. It is essential to follow the care instructions when washing with Flame-Resistant PPE. In most cases, you should not use bleach, hydrogen peroxide, or fabric softeners when washing.

ARC-RATED

All Arc-Rated PPE is also Flame-Resistant. PPE cannot be considered Arc-Rated without meeting Flame-Resistant standards. You can expect the same insulation and prevention of ignition mentioned above and the added protections covered in the following breakdown.

HOW TO DETERMINE THE ARC-RATING NEEDED

Employers and equipment manufacturers are required to conduct an Arc Flash Risk Assessment. This assessment will determine what PPE is required. NFPA 70E - 2021 Edition gives the option of two assessment methods. It is important not to mix and match the results of one method with the standards of the other.
  • The Arc Flash PPE Category Method
  • The Incident Energy Analysis Method

METHOD 1: THE ARC FLASH PPE CATEGORY METHOD (TABLE METHOD)

The Arc Flash PPE Category Method relies on the tables provided by NFPA 70E. If the working conditions fall within the parameters of one of the table options, you can utilize this method. This method requires you to collect information on the equipment, such as voltage, fault current, fault clearing time, and working distance. You match the info you've collected with the table, and the table will tell you which PPE category is required.
This method's PPE categories are defined in Table 130.7(C)(15)(c) in 2021 NFPA 70E, which breaks this rating system down into four categories. Each category has a minimum cal/cm2 rating.

Category 1 Arc Flash PPE Method – Min rating 4 cal/cm2

REQUIRED:
  • Min. 4 cal/cm2 rated long sleeve shirt and pants or coveralls
  • Min. 4 cal/cm2 rated wrap around face shield or flash suit hood
  • Min. 4 cal/cm2 rated gloves or rubber gloves with leather protectors
  • Hard Hat, safety glasses, hearing protection
  • Leather Footwear
AS NEEDED:
  • Arc-Rated High Visibility Safety Apparel
  • Arc-Rated outerwear (jackets and parkas)
  • Arc-Rated rainwear
  • Arc-Rated Liners for hard hats

Category 2 Arc Flash PPE Method – Min rating 8 cal/cm2

REQUIRED:
  • Min. 8 cal/cm2 rated long sleeve shirt and pants or coveralls
  • Min. 8 cal/cm2 rated wrap around face shield with min. 8 cal/cm2 rated balaclava or flash suit hood
  • Min. 8 cal/cm2 rated gloves or rubber gloves with leather protectors
  • Hard Hat, safety glasses, hearing protection
  • Leather Footwear
AS NEEDED:
  • Arc-Rated High Visibility Safety Apparel
  • Arc-Rated outerwear (jackets and parkas)
  • Arc-Rated rainwear
  • Arc-Rated Liners for hard hats

Category 3 Arc Flash PPE Method – Min rating 25 cal/cm2

REQUIRED:
  • Min. 25 cal/cm2 rated flash suit (jacket, pants, hood)
  • Min. 25 cal/cm2 rated gloves or rubber gloves with leather protectors
  • Hard Hat, safety glasses, hearing protection
  • Leather Footwear
AS NEEDED:
  • Arc-Rated High Visibility Safety Apparel
  • Arc-Rated outerwear (jackets and parkas)
  • Arc-Rated rainwear
  • Arc-Rated Liners for hard hats

Category 4 Arc Flash PPE Method – Min rating 40 cal/cm2

REQUIRED:
  • Arc-Rated High Visibility Safety Apparel
  • Arc-Rated outerwear (jackets and parkas)
  • Arc-Rated rainwear
  • Arc-Rated Liners for hard hats
A misconception is that these ratings are for hot or live equipment. It does not matter if you’ve cut power to the box you are working on. If you are taking the front plate off, hot or not, you have to be geared up with the appropriate PPE.
It is also not recommended to protect yourself right at the threshold. That means if you are working on a box rated at 25cal, you should be wearing more than 25cal PPE. In fact, with all the recent advancements in materials and PPE designs, it's easy just to opt for a 40cal kit. These new suits have lighter fabrics that are easier to move in, the masks are more durable, fog resistant, and easier to see out of, and the kits are easier to pack. Overall, they are much more comfortable to wear and have a lot more features that make them less of an issue compared to how the old suits used to be.

METHOD 2: INCIDENT ENERGY ANALYSIS METHOD

The Incident Energy Analysis Method requires an electrical engineer to assess the arc flash risk in your facility. The engineer will inspect the equipment and the electrical systems in the facility. Using the collected data, they will calculate the Arc Flash Risk Assessment.
This method’s PPE categories are defined in Table 130.5(G) in 2021 NFPA 70E, which breaks this rating system down into two categories. Each category has a minimum cal/cm2 rating.

Category 1 Incident Energy Analysis Method – Min rating 1.2 cal/cm2, Max rating 12 cal/cm2

REQUIRED:
  • Arc-Rated (min equal to max estimated incident energy) long sleeve shirt and pants or coveralls or arc flash suit
  • Arc-Rated (min equal to max estimated incident energy) wrap-around face shield with Arc-Rated balaclava or flash suit hood
  • Arc-Rated (min equal to max estimated incident energy) rated gloves or rubber gloves with leather protectors
  • Hard Hat, safety glasses, hearing protection
  • Leather Footwear
AS NEEDED:
  • Arc-Rated High Visibility Safety Apparel
  • Arc-Rated outerwear (jackets and parkas)
  • Arc-Rated rainwear
  • Arc-Rated Liners for hard hats

Category 2 Incident Energy Analysis Method – Min rating 12 cal/cm2

REQUIRED:
  • Arc-Rated (min equal to max estimated incident energy) long sleeve shirt and pants or coveralls or arc flash suit
  • Arc-Rated (min equal to max estimated incident energy) wrap-around face shield with Arc-Rated balaclava or flash suit hood
  • Arc-Rated (min equal to max estimated incident energy) rated gloves or rubber gloves with leather protectors
  • Hard Hat, safety glasses, hearing protection
  • Leather Footwear
AS NEEDED:
  • Arc-Rated High Visibility Safety Apparel
  • Arc-Rated outerwear (jackets and parkas)
  • Arc-Rated rainwear
  • Arc-Rated Liners for hard hats

THE LABEL

Given the information covered in this article, the label on Arc-Rated PPE is straightforward.
Arc-Rated PPE lists all the standard label information you usually see on any garment. This includes the brand, part number, or SKU, where the PPE was made, size, care instruction, and materials.
Additionally, the label will list all of the conforming Flame-Resistant standards and Arc ratings. The Flame-Resistant standards are set by the National Fire Protection Association (NFPA), and the American Society sets the Arc-Rating for Testing and Materials (ASTM).
If applicable, find the ANSI/ISEA 107 class rating on the tag. This class system defines the ratio of retroreflective to fluorescent background material on your PPE.

MAIN TAKEAWAYS

This article covers dense technical information, but it is essential for worker safety. Arc flashes happen incredibly fast and leave severe damage.
If you are an employee who is unsure of what PPE you need to remain safe. In that case, your employer will be able to provide you with the information and appropriate PPE required. If you are an employer or facility owner who is unsure what level of PPE is needed when in doubt, hire someone to conduct an Arc Flash Risk Assessment for you.
The Arc Risk Assessment provides you with guidance beyond what PPE to wear. It also gives guidelines on procedures that need to occur in and around your facility.
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