Arc rated flame resistant (AR/FR) garments are required to have labels that clearly announce the level of protection they provide. One rating that appears on these garments is the CAT rating, short for PPE CATegory. The CAT rating tells wearers at a glance the category of protection the garment provides against injury in the event of an arc flash.
Garments also carry a more precise measure of protection, labeled in calories (CAL). Calories are the units of measure used to describe the force of an arc flash. So a CAL rating of 8.7, for instance, means that the garment in question will prevent injury when subjected to an arc flash of 8.7 calories or less.
The goal of the rating is to help you choose the right clothing to keep you safe on the job.
Fabric type and garment design both factor into the number of calories a garment can withstand. The CAT rating is designed to simplify the process of choosing AR/FR clothing that provides protection adequate to the hazard being faced. CAT ratings group clothing into four easy to interpret categories:
|Minimum Arc Rating
For instance, any garment with a CAT rating of 2 will protect the wearer against an arc flash of 8.0 calories or less. If you’re working in an environment where your hazard analysis reveals the potential for an 11 calorie arc flash, you would want to choose a CAT 3 garment.
For further explanation, watch the video below:
Often, employers know the maximum arc flash strength their workers are likely to face on the job. This allows them to specify that all AR/FR clothing they provide to their workers must carry the appropriate CAT rating.
For workers who have been in the industry for several years, there could be some confusions as to how CAT ratings compare to HRC ratings. The easy answer is, they are essentially the same thing, with different names. Revisions to NFPA 70E in 2015 included a change in terminology. The term Hazard Risk Category (HRC) was changed to PPE Category (CAT). The principles behind the ratings did not change, but all AR/FR clothing manufactured after the change was expected to show the CAT rating. For a more complete explanation of the change from HRC to CAT, see our blog post on the subject.