Q: We understand that OSHA 1910.269 recommends and NFPA 70E requires Arc-Rated shirts to be tucked in.
We are an electric utility cooperative. If an AR (Flame Resistant, Arc-Rated) t-shirt is worn that matches the hazard and the AR t-shirt is tucked in and an outer AR shirt is also worn, primarily for warmth, does the outer AR shirt have to be tucked in? Can this cause a “chimney effect” and cause arc facial burns to be worse from the arc coming up through the shirt to the face? A consultant trained our workers about this dangerous “chimney effect”, but it doesn’t make sense to us or to our management.
A: We typically recommend tucking in an AR shirt…
…for added protection and to lower the risk of direct skin burns (if no AR t-shirt is worn), and to lower the risk of undershirt ignition (if the undershirt is made of ignitable material, like cotton).
In the case that a non-AR cotton undergarment is worn and ignites, there can be a substantial “chimney effect”. This is when the outer AR shirt, left open and untucked, acts as a “chimney” allowing air to feed the fire from the bottom of the untucked shirt and cause the non-AR undershirt to burn more quickly by feeding the fire with oxygen from below.
There is NO “chimney effect” if the undershirt is an AR shirt and doesn’t ignite. You indicated a “consultant” had informed you this was some function of the arc under untucked shirts. I can assure you that is not the case.
Tucking in the outer AR shirt when wearing an AR undershirt could increase protection levels in some instances. If one layer is matched to the rating, leaving an additional AR shirt on top untucked, this will not increase risk of injury from an arc exposure. But the total protection of some areas under the untucked shirt could have only the one layer of AR for protection. If this layer is matched to the hazard, the company should be in compliance with the OSHA standard 1910.269.
While this is an unusual question, it is important to accurately portray the facts. Scaring workers into compliance with something that doesn’t make sense undermines our other facts in the future. I prefer workers to “tuck, button and roll” the shirt properly. Your scenario adds no risk, but it just doesn’t take full advantage of an added layer of protection.
Language in NFPA 70E and OSHA
NFPA 70E states PPE coverage clearly in 130. 7(C)(9)(d):
“Covrage. Clothing shall cover potentially exposed areas as completely as possible. Shirt and coverall sleeves shall be fastened at the wrists, shirts shall be tucked into pants, and shirts, coveralls, and jackets shall be closed at the neck.”
OSHA does it in a roundabout way. My statement in the video (see below) is based on a conversation with the primary author of 1910.269. He indicated that not wearing clothing as intended (most manufacturers will recommend tucking in AR and FFR clothing) would be a violation of the general duty clause at least and a direct violation of 1910.269(l)(8)(iv)(B) if the undergarment ignited or melted.
“The employer shall ensure that the outer layer of clothing worn by an employee … is flame resistant under any of the following conditions: An electric arc could ignite flammable material in the work area that, in turn, could ignite the employee’s clothing …”
My data, done for APS and other utilities show that a cotton t-shirt ignites below the arc rating of the shirt when the outer AR shirt is untucked.
“The employer shall ensure that each employee who is exposed to hazards from flames or electric arcs does not wear clothing that could melt onto his or her skin or that could ignite and continue to burn when exposed to flames or the heat energy estimated under paragraph (l)(8)(ii) of this section.”
Based on this passage, Danny Raines wrote the following in Incident Prevention magazine, “Based on this statement, employees should be sure to prohibit employees from wearing synthetics whenever they could be exposed to arcs or flames. Additionally, both employers and employees should be aware that any arc-rated FR shirts should be tucked into pants and buttoned at the sleeves and neck. If skin is exposed, the clothing will not provide maximum protection.”
Employers can certainly argue this point. But it is definitely BEST PRACTICE.
I have seen more than one individual burned from arc energy coming under an untucked shirt and a few with clothing ignitions that I believe were directly related to not tucking.
Our lineman’s training covers this and many other topics in our video. Live instruction is available as well. We also offer a Train the Trainer class to allow the training materials to be licensed to the utility.
- Find out more about renting, purchasing, or licensing the video Arc Flash Awareness for Utilities.
- More info about our Arc Flash Safety for Utilities (1910.269) Train the Trainer class.