The Complete Guide to Hazard Level Risk Ratings

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The Complete Guide to Hazard Level Risk Ratings

To protect and educate electrical workers, the NFPA categorizes the risk of worksites into four levels. The NFPA sets the standard for hazard level risk ratings at workplaces, and our complete guide will go through each category and explain what it means to workers.

We’ll also break down some essential terms to understand and how they relate to the hazard risk ratings of the NFPA.

What Is the NFPA?

The NFPA sets the standard of hazard level risk, but what is the NFPA? The National Fire Protection Association was established back in 1896 to reduce the risk of fire and hazards in homes and worksites to improve the quality of life.

To achieve this goal, the NFPA establishes codes and standards while conducting research and disseminating literature and best practices to businesses, governments, and regular people. The NFPA is considered the world’s leading advocate of fire prevention and protection, and its standards are adopted globally.

What Is the NFPA 70E?

One of the standards created by the NFPA is NFPA 70E. The NFPA 70E is the standard for electrical safety in the workplace, including all OSHA-compliant worksites.

The NFPA 70E was the first nationally recognized code for electrical safety in the US, and the NFPA released it in 1976. The standard is updated regularly, with the latest edition released in 2021. Technically speaking, the NFPA 70E applies to all workplaces, but it is generally enforced on construction sites, industrial plants, or anywhere else where workers could encounter electrical harm.

NFPA Hazard Terms To Know

Throughout NFPA 70E, there will be a few industry terms and abbreviations thrown around, so we’ve put together a short glossary of the words and acronyms you need to know to understand the code adequately.

ARC Rating

ARC rating essentially refers to how safe the protective clothing is and how much a worker needs according to the Hazard Risk Category (HRC). The NFPA determines the rating by the minimum number of calories per square centimeter (Cal/cm2) necessary to pass through a given fabric to cause a likely probability of second or third-degree burn.

The ARC rating is measured by Cal/cm2, so the terms are sometimes interchangeable. The higher the ARC rating, the more protection a worker needs to avoid severe harm or possible death. ARC ratings are printed on garments by the manufacturers, so workers know precisely how protective the clothes are.

Calorie (Cal/cm2)

The Cal/cm2 measurement refers to calories per square centimeter. The calorie in this context is not the nutritional kind we may initially think of, but the energy required to raise one gram of water one degree. (Cal/cm2)

The higher the Cal/cm2, the greater the hazard risk, the higher the HRC level, and the more protection required. For comparison, second-degree burns typically occur at 1.2 Cal/cm2.

Electric ARC

An electric ARC is another term typically used by the NFPA as a cause for hazard and risk on a worksite. Essentially, an electric ARC is the passage of a significant electric current through ionized air.

An electric ARC typically occurs when a circuit is overloaded or overheats. They’re highly dangerous, though, and can result in fatality for workers without adequate protection.

ARC Flash

An ARC flash is also another danger on high HRC level worksites. When an electric ARC releases an explosive amount of energy, it’s deemed an ARC flash.

The flashover of electric current leaves its intended path and travels through ionized air to another conductor. It’s a violent phenomenon, and severe injury or death can occur if a human is nearby.

The NFPA 70E Hazard Risk Category (HRC) Levels

Now, we come to the HRC levels of the NFPA 70E. The NFPA distinguishes the levels by the minimum Cal/cm2 present for the site. The risk levels range from zero to four, with level zero meaning little to no risk and level four implying extreme risk.

We’ll also share the recommended fire-resistant (FR) clothing that workers should wear at the level to ensure their safety. The typical FR garments include:

  • FR undergarments (underwear, undershirt)
  • FR shirt
  • FR pants
  • FR coveralls
  • FR jacket
  • FR bibs
  • Multi-layer flash suit

Hazard Risk Category 0 (Cal/cm2: 0)

It may seem strange, but the HRC levels begin at zero. This HRC level means there’s little to no risk of burn or injury for electrical workers, but it still recommends sensible, if not protective, clothing.

Electrical workers don’t need FR clothing for this level of risk, but the NFPA 70E still recommends they err on the side of caution. The code advises cotton undergarments, a long-sleeved shirt, pants, safety glasses, and leather gloves.

Hazard Risk Category 1 (Cal/cm2: 4)

The first HRC level implies some risk to electrical workers and requires FR clothing, but one layer should be enough for adequate protection. One layer of clothing means an FR shirt and FR pants or FR coveralls, whichever you prefer.

It’s still wise for electrical workers to utilize cotton undergarments, glasses, leather gloves (or insulating gloves), and leather shoes to ground them. NFPA 70E also recommends workers wear a hard hat with an ARC-rated face shield instead of a standard protective construction helmet.

Hazard Risk Category 2 (Cal/cm2: 8)

At the HRC level two, the Cal/cm2 doubles to 8, and with that added risk, workers should add another layer of protective garments. The NFPA 70E requires workers at an HRC level two worksite to have FR undergarments (underwear and undershirt) and a FR shirt and pants.

Or, as before, workers can opt for FR undergarments with FR coveralls or even an FR jacket and fire-retardant bibs. Essentially, electricians should have two or more layers of FR protection.

Workers should employ an ARC-rated flash hood, a FR balaclava, or an ARC-rated hard hat with a face shield for facial protection. At this level, electricians should also use ARC-rated leather gloves.

Hazard Risk Category 3 (Cal/cm2: 25)

There’s a substantial increase in risk from HRC level two to level three, so FR protection becomes even more essential to avoid serious harm. The code advises two to three layers of FR protection. The individual worker can choose their combination of FR undergarments, shirt, jacket, pants, and coveralls in whichever way they prefer.

Accessories like hats, shoes, and gloves are even more critical, so ARC-rated garments and materials are vital to working safely.

Hazard Risk Category 4 (Cal/cm2: 40)

HRC level four is the highest NFPA 70E risk rating and implies an extremely hazardous workplace. Workers should at least have three layers of FR protection, but experts highly recommend four.

Only at HRC level four are heavy-duty, multi-layer flash suits common, and even with those, the code advises workers to also have an FR shirt and pants underneath the suit. At hazardous sites like these, every precaution should be taken.

We hope our guide on the hazard level risk ratings helps you find the proper protective gear for you or your employees to work safely. Remember that it’s always better to be overly cautious in cases of electrical burns instead of being careless about safety.

The Complete Guide to Hazard Level Risk Ratings
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