I’m sure that title raised a few eyebrows but before you send me an email telling me how I got this wrong, hang in there for the rest of the thought. I receive questions about this phrase on a pretty regular basis.
It’s no secret that 1.2 cal/cm2 is the generally accepted value of incident energy exposure where the onset of a second-degree burn may occur. This is also the value that triggers the need for arc rated clothing and protective equipment.
However, having a prospective incident energy below 1.2 cal/cm2 can cause confusion as some will place the phrase “NO ARC FLASH HAZARD EXISTS” on the arc flash label as a result. When I ask why this phrase is on the label, I receive the response that it’s because the incident energy is less than 1.2 cal/cm2. – BEEP – Wrong Answer!
If the prospective incident energy is less than 1.2 cal/cm2, remember that is at the working distance and it only means that it is below the threshold where the onset of a second-degree burn may occur. It does NOT mean there is no injury possible. What about first-degree burns? What about the hands or other parts of the body being closer than the working distance? What about… You get the idea. There IS still a hazard it is just not commonly considered a major hazard that requires arc rated PPE at the working distance.
I am asked about using this phrase so often that a while ago I decided to ask a more general survey question about arc flash hazards at 208 Volts at the website www.ArcFlashForum.com. I was surprised to see almost 20% of the respondents to the survey indicate they did not believe an arc flash hazard exists at 208 Volts.
The survey and discussion are found here: https://brainfiller.com/arcflashforum/viewtopic.php?f=33&t=5416
The working distance is very important because it is the distance from the arc flash source that is used to calculate the incident energy where a worker’s head and torso would likely be located. This makes understanding the working distance a very important part of an electrical safety training program. Just because the incident energy is listed as less than 1.2 cal/cm2 at 18 inches for example, doesn’t mean it will be that low for hands and other parts of the body that are closer. It increases as the working distance decreases.
I can hear this scene being played out in a legal setting.
Attorney: “I am sorry to hear that you received a burn injury on your hand but why where you not wearing arc flash protection?”
Response: “Because the label stated – No Arc Flash Hazard Exists”
Really? Fade to black, game over.