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September 13, 2016

Hey Ninja,

My new job requires that I get some gear with a CAL rating high enough to fulfill the needs of HRC Category 2. What are HRC Categories and CAL ratings, and what do I need to get to meet the requirements?

- Calvin CALiente

Hey Calvin! First things first, let’s clear up what the HRC, or Hazard Risk Category, really is. The National Fire Protection Association (NFPA) has identified 4 hazardous risk category levels, which are numbered by severity from 1 to 4, 1 being the lowest and 4 the highest. HRC is the level of arc flash/fire protection clothing you must wear to protect against a minimum level of energy in an accident, measured in calories per centimeter squared. Each level of the HRC chart or table is assigned a minimum CAL rating for personal protective equipment. The levels are as follows:

  • HRC 1 - 4 cal/cm²
  • HRC 2 - 8 cal/cm²
  • HRC 3 - 25 cal/cm²
  • HRC 4 - 40 cal/cm²

There is also an HRC 0 rating which just means that FR clothing is not required, but clothes must be non-melting or untreated natural fibers.

Now that we’ve cleared up the HRC and the requirements for each level, we can look into CAL ratings and how they relate to each level. Clothes, especially Flame Resistant (FR) articles of clothing, have a CAL rating provided by the manufacturer. This is based on the materials used in the production, or any possible additives used to provide additional protection. Manufacturers who make articles of clothing with FR qualities will provide each item’s CAL rating. To achieve the required CAL rating for each HRC, you’ll have to layer the appropriate items and meet the minimum required CAL score. There are standardized suggestions for each HRC level, but certain clothes may have a higher rating which will surpass the minimum requirements. Companies like Drifire manufacture products that have higher CAL ratings than normal everyday articles of clothing. You’d get more CAL credit from a Drifire FR Ultra-Lightweight Short Sleeve Tee than you would from a standard tee.

If we take the HRC table from above and add in the suggested FR clothing for each level, it would look like this:

Hazard Risk Category
Common FR clothing combinations
Minimum CAL rating (Cal/cm²)

  1: FR shirt and FR pants   

  2: FR coveralls   

  3: Single base layer of FR protection   


  1: FR under garments (undershirt, underwear), FR shirt, FR pants   

  2: FR under garments, FR coveralls   

  3: 2 or more layers of FR protection   


  1: FR under garments, FR shirt, FR jacket, FR pants, FR coveralls   

  2: 2-3 or more layers of FR protection   


  1: FR under garments, FR shirt, FR jacket/coat, FR pants, FR coveralls   

  2: FR under garments, FR shirt, FR pants, multi-layer flash suit   

  3: 3-4 or more layers of FR protection   



So Calvin, this table can help you see that for your HRC 2 requirement, you’d need FR undergarments and 2 or more layers of FR protection like a FR shirt and FR pants. Your job may prescribe a specific combination that you are required to use, but this should give you a good outline of the basics.

Until next week, you can always reach the Ninja at

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