This week’s question is very subjective and is based on all kinds of variables such as lighting, eye sight etc. For an average person under normal conditions:

What is the MAXIMUM distance where the typical arc flash label details are still readable?

Less than 4 ft. (1.2 M)
Between 4 and 8 ft. (1.2 to 2.4 M)
Between 8 and 12 ft. (2.4 to 3.7 M)
Something greater than 12 ft. (3.7 M)
It depends

It really doesn't matter because they should be posted where they are accessible BEFORE you need to know that. The typical example is the OUTSIDE of an enclosure but another example would be at the base of the pole/mast below an overhead cutout/disconnect. Risk of an exposure to an arc flash event prior to this is almost none.

It depends on what the arc flash boundary is. You certainly would not want to be able to read that the AFB is 10 feet only once you are 3 feet away. It should be recognizable what the boundary is when you are standing at the boundary.

Before my cataract surgery last year, about 1 ft.
Now probably >4 ft.
Sorry, couldn't resist

Hi Jim,

I agree with the "all kinds of variables" factor. Perhaps could one consideration be the average age of the workforce in a particular facility? If the average age is above 45 then one may consider a larger label with larger fonts. I have seen on a few occassions on an MCC where one larger label was installed in a conspicious location on the MCC in oppose to smaller labels on each cell. Myself being over 55 I would prefer a larger label with larger fonts that could be read further away

Our standard label has the energy level in a much larger font than any other numbers or text on it for just that reason.

It depends of the label size, font and information on it. Usually the labels shows a lot of information not required by NFPA.

I think that if the worker prepare the task, allways could read it before energized parts are exposed.

It's not uncommon on switchgear in our facility for the number to be 80 feet plus. We would be required to post all of the labels on all the room doors in order to accomplish the goal of having the labels readable outside the boundary.

Great comments everyone - thanks. I was originally asked by someone to post a question about what font size people use but thought asking about the distance and readability was really the issue. Yep, I'm falling into the aging category too as much as I try to resist it.

https://deepblue.lib.umich.edu/bitstrea ... sequence=2
http://www.usscfoundation.org/USSCSignL ... sThumb.pdf

Aside from being very subjective, there are a lot of details that make something as "simple" as legibility anything but simple. When I last looked into this the one thing that was absolutely clear is that there is no agreement among standards.

Also although 70E and others all state that ANSI Z535 is the proper standard for safety signs, almost nobody actually follows it! But somewhat more troubling is that compliance with ANSI Z535 doesn't seem to enhance compliance with safety signs. See for instance:
http://pro.sagepub.com/content/49/19/1785.abstract

Under 4' visibility is sufficient at the facilities I have worked at.

Larger labels would be a liabilty to find space to install in a fashion that didn't leave them prone to weather damage.

Putting them outside the Arc Flash Approach radius would also be confusing and require a road map of which labels are for which equipment.

Some of this comes down to familiarity, the workers will be looking for a label on the equipment, and then suit up in PPE prior to doing the work.

Arc flash boundary does not come into play until work is being done on the equipment. The label will be read right at the equipment, and the workers will take the proper precautions. This involves wearing the right PPE for the incident energy as well as securing the arc flash boundary (and other boundaries) so no one crosses over while work is being performed.

I'd agree pretty much universally in areas where 70E applies (industrial equipment) which is for the most part enclosed these days. The exception is open air equipment, particularly overhead distribution equipment, where approaching it is somewhat problematic in the first place.

That's not to say that there aren't things that can't be done. One particular case that I can think of was a large overhead pole line system with over 100 pieces of equipment attached to it ranging from small lighting transformers up to large substations for pumping stations. Going through the calculations found that except within the first quarter mile of the main substation, incident energy was well below 1.2 cal/cm2 at a distance of 8-10 feet away, what they used for hot sticks for moving jumpers, pulling cutouts, etc. So unless you were doing rubber glove work, "arc flash" was kind of automatic.