The 2015 Edition of NFPA 70E 130.7(A) Informational Note 3 stated:

Informational Note No. 3: When incident energy exceeds 40 cal/cm2 at the working distance, greater emphasis may be necessary with respect to de-energizing when exposed to electrical hazards.

This note was deleted with the 2018 edition. Most people were using the signal word DANGER with a RED background for incident energy above 40 cal/cm2 based on this informational note. (Red/Danger is based on ANSI Z535 – this might be different in other countries)

This question is to check the pulse of the industry 5 years after this note was deleted.

For arc flash studies today, do you still use RED/DANGER on labels above 40 cal/cm2?
Yes
No
It depends
Your comments are always welcome!

There is no direct correlation between incident energy and arc blast pressure. This was identified by Dr. Ralph Lee in his original research from the late 1980s, but unfortunately a public comment was added to NFPA 70E that implied there was and at the 40 cal/cm2 incident energy level. Which happens to correlate with the old HRC 4 or now Arc Flash PPE Category 4.

Dr. Ralph Lee's research was published in the IEEE Yellow Book which is now IEEE 3007 series. You can view the graph that is included.

Danger signal pane should be at 140.1 cal/cm2 based on an employer's compliant Electrical Safety Program including a documented work task based risk assessment procedure.

Unfortunately over the last decade consulting engineers completing arc flash hazard incident energy analysis studies included an error in their reports and was propagated by the power system software vendors that wrongly automatically included a column in the "Results Table" for incident energy analysis that ≥40.0 cal/cm2 as "Dangerous" and "No PPE Exist." Both of these statements were and are false!!!!

Then the software automatically generated Danger single pane equipment labels. Software should not be used to make risk based decisions. Risk assessment is completed by the employer.

Employer's that commissioned studies were misinformed with respect to what I call the "40 cal myth!!!"

There is a lot of misinformation and disinformation related to abnormal arcing fault sustainability and arc flash published in social media, in reports issued and by "arc flash trainers." This is unfortunate.

That said employers can control the narrative related to electrical hazard identification/classification, detailed defendable risk assessment procedure and ensuring residual risk is as low as reasonably practicable by development, implementing and auditing a compliant Electrical Safety Program.

More than willing to discuss/debate this with any "arc flash trainer," consulting engineer etc. My email is terry.becker@twbesc.ca. or call me 587 433-3777.

Electric shock leading to electrocutions (which incident statistics prove) needs attention. Also be aware of electric shock sequelae!

What Jim said is correct. But most of the time, we use 40 calories as a break point between Warning and Danger labels. Here is how we go at this. We explain to the client that this is subjective decision and that the 40 calorie limit was a legacy requirement. That this 40 calorie limit is no longer enforced. That it was likely something that was decided based on the available PPE at that time. Generally, after clients hear this, they will still go with 40 calorie break point between warning and danger. What I usually hear is that above 40 calories, they will bring in a contractor to do the work. Sometimes it's another level, but it's their choice.

If the signs/labels are following the ANSI Z535 standard (not required by NFPA 70E), they would be using the following definitions.
From ANSI Z535.2-2011:
4.11.1 DANGER: Indicates a hazardous situation that, if not avoided, will result in death or serious injury. This signal word is to be limited to the most extreme situations.
4.11.2 WARNING: Indicates a hazardous situation that, if not avoided, could result in death or serious injury.
4.11.3 CAUTION: Indicates a hazardous situation that, if not avoided, could result in minor or moderate injury.

A long time ago the idea that 40 cal/cm^2 was a magical delineating line between Warning and Danger got started. Although that idea is debunked and many of the basis concepts outdated, Danger vs Warning label headers is not settled. It is still quite common for clients to specify that they want Danger at 40 and greater and Warning for less than 40.

Some of it is based on risk tolerance. For some they want to remain consistent with past practices. Some of it is based on very few people actually reading the ANSI Z535 standards and knowing what the differences are between the Danger and Warning definitions. Some of it is based on a desire to make certain IE level signs stand out. And some not knowing that there is no magical line at 40 cal.

Danger - will result in death or serious injury. What incident energy level will result in death? That isn't fixed. What is meant by "serious" injury?

Warning - could result in death or serious injury. What incident energy level could result in death? Again, there isn't a fixed level. Also, we have "serious" in there again. Is the warning level of "serious" different than the danger level of "serious"?

Hazard notifications signs/labels for arc flash are often also used for voltage hazard notification. In that case the risk of death/serious injury from the voltage hazard would also need to be considered.

So really, as long as the labels/signs are consistent throughout the facility/company and consistent with their electrical safety policies and procedures, does it really matter as long as they are at least using a Warning signal word?

If PPE is required, as determined by 130.5 and an employee didn't wear it, would any of the following occur?

"permanent loss of function or significant disfigurement"
"substantial and prolonged medical treatment required;"
"long periods of disability;"
"considerable pain and suffering over long periods of time."
If it would, then it is considered serious injury by the 535 standard, and therefore should use the word DANGER.

All of my arc flash labels that indicate any arc rated PPE is required use 'DANGER' -- I'll explain why.

We've already determined that injury is likely, by the requirement of PPE.

To deal with injury VS. serious injury, I would ask everyone with an opinion here if, they have suffered a burn injury from a scenario that required arc flash PPE but they weren't wearing any. I'm sure some of you have(that's probably why you're here.) I posit, if we ask the people who have been injured that way, we would find that the above list would be more often applicable then not, if not always. The unrelenting pain of a burn is not to be considered lightly. Permanent damage from burns happens quickly. Ask their family if it was just an injury or a serious injury.

When we're considering the safety of our employees, why would we debate injury VS. serious injury when it's determined that either is already likely?

I feel like this question is about whether one would be blown to smithereens if there is a 40 cal event, then just "Will serious injury occur to our employee if they don't wear the required PPE?".

Again, if it's likely that an injury will occur and possible that that injury would be serious, what are we actually talking about here?

According to the ANSI definitions, the only difference between Danger and Warning is WILL and COULD (the "serious" injury is a given, and I would consider 2nd degree burns to fit the definition of serious injury). So would the serious injury occur if someone forgot to wear any PPE? Probably not. But COULD the serious injury happen? Absolutely.

Saying "Danger" indicates the injury "will" happen, suggesting there is an arc flash event every single time you operate the equipment. I believe "warning" would be the proper header in the case of an arc flash label regardless of incident energy.

I cannot provide real-time information on current industry practices. However, the decision to use RED/DANGER on labels above 40 cal/cm2 for arc flash studies often depends on various factors, including company policies, industry standards, and regional regulations. It is recommended to stay updated with the latest editions of relevant standards and guidelines, consult with safety professionals, and follow any specific requirements in your jurisdiction. Safety practices may evolve, so it's crucial to be aware of the most recent guidelines and adopt best practices accordingly.

I'd say it depends. Evaluating the arc flash hazard based on incident energy alone without factoring in how fast the energy has been delivered is similar to measuring velocity in miles without indicating time interval (seconds / hours / years). Namely, any fixed amount of energy produces drastically different results when delivered during short or long time interval. For that matter, the 40 cal/cm2 measure alone without time interval is meaningless. It is about the energy one is exposed to within half an hour in sunny day on the beach. On the other hand, 40 cal/cm2 is an exposure to an explosion of roughly 1 kg of TNT at 18 inches distance from the source.

Thank you, I can now see an element of confusion more clearly.

Warning and danger labels typically indicate hazards in a straightforward manner, such as "Touch this and x will or can happen" or "Step there and y will or can happen", indicating a lack of controls for a hazard or their bypass will lead to potential injury. However, when it comes to arc flash labels, the approach often deviates from this standard.
The primary issues are:
1. Inconsistent application of the full ANSI definition of DANGER vs. WARNING.
2. The inclusion of controls such as PPE as a factor in deciding when to use DANGER vs. WARNING labels.

The shift from using DANGER in accordance with the standard is attributed to the belief that overuse leads to "banner blindness" or "systematic desensitization", diminishing the label's impact. This is a significant concern, especially if DANGER is truly warranted. It seemed relevant because even when rated PPE was applied (controls), possible injury from a hazard was still present. We have more data now that shows, at known rates, properly applied PPE will perform as expected. That changes things in that regard.

The key question is whether we are treating these labels like virtually all others are treated (addresses the hazard present when controls are bypassed or not in place), or if we are creating our own standards because these labels are meant for qualified workers within a safety program, and not employees at large.

If we adhere to the usual application of the ANSI standard, most arc flash labels should indicate DANGER when the energy is over 1.2cal.

If it is decided to tailor a new standard for these labels and their use under an Electrical Safety Program (ESP), this opens up a discussion I'd like to see about energy rates versus the risk of Overcurrent Protective Device failure and its implications for reducing the efficacy of Personal Protective Equipment (PPE) in such events. Currently, our program creates "headroom" (the distance between the PPE rating and the IE) in our risk assessments to mitigate this.

For now, I will continue using DANGER labels as per standard practice and will only revise this approach when a clear standard is established.

Assuming the labels are for use by qualified personnel under an ESP, the choice of warning or danger does not impact the risk assessment as currently prescribed. It's therefore moot.

IMO-The matter remains unresolved until a definitive standard is established.