Wearing flame resistant clothing can provide the necessary thermal protection to shield workers from an Arc Flash. Once the source of ignition is removed, the FR garments will self-extinguish, greatly limiting the severity of a burn. In many cases, they can mean the difference between a minor accident and a tragic fatality.
See our range of Arc and Flame resistant clothing here.
Measuring Arc Flash Heat
Arc Thermal Performance Value (ATPV) is the exposure on a material that results in a sufficient heat transfer through the material for a 50% probability of the onset of a 2nd-degree burn. An ATPV rating is assigned to FR clothing to indicate the level of protection that is required. In other words, the higher the rating (cal/cm2), the greater the protection.
Arc Rated Clothing Flame Resistance Levels
A popular testing method for flame resistance of Arc Flash clothing is to use the HRC – Hazard/Risk Category. This was recently changed to PPE level.
The HRC or PPE level is measured by the minimum amount of calories/cm2.
Four Categories of Arc Flash PPE
The 2018 edition of NFPA 70E changed the way measurement is completed and PPE is selected. This most recent edition removed the concept of Hazard/Risk Categories and the option wear Non-FR/AR natural fiber garments in HRC 0 was eliminated. The standard now uses PPE categories which are based on an incident energy analysis. NFPA 70E (2018) now gives four categories of PPE, with each category including the minimum Arc Rating value for the required PPE. The PPE manufacturer is required to obtain and identify these arc ratings in their products which, simply put, represents the amount of incident energy (in cal/cm2) on a material or a multilayered system of materials that results in a 50% probability to cause the onset of a second degree skin burn injury.
- HRC 1 : 4 cal/cm2
- HRC 2 : 8 cal/cm2
- HRC 3 : 25 cal/cm2
- HRC 4 : 40 cal/cm2
