The blast pressure from an arc flash is often cited as a concern for larger incident energy values. This weeks question:

Have you ever known/heard of anyone being injured directly from arc flash blast pressure?
Yes
No

If yes, we would love to hear the details!

Oops, I voted no and then I remembered a coworker.
He tells the story of a time he was making voltage measurements using a hand-held meter. There was a fault and the blast pressure 'threw' him away from the gear and against the safety railing around the mezzanine which prevent additional fall injuries. His injuries were moderate to severe due to his impact.

Out of 160 incidents investigated I don't know of any severe injuries. Contusions and bruises and one cracked rib from a fall getting away from the arc. Many have been "blown back" but I none suffered collapsed lungs or anything one would usually associate with a overpressure/dynamic pressure event in the magnitude of a bomb or a grenade. Our new paper for IEEE-ESW 2016 has some interesting measurements of a door ejection and pressure inside a box and after the door starts to move. Need more work on this but most of the training I hear has overblown this factor for little evidence. I know of no one who died from direct blast. Heard of ONE who died from a fall over a safety rail. Seen video of people blown back but one was another person who hit them trying to get away from a low fault current arc. Pressure is a function of fault current and arc voltage but pressure is very limited by the volume so once the door moves the pressure is MUCH less. In one experiment we mannequin is moved about 5 feet by the door with without the door the 70 lb. mannequin doesn't even move.

We need more research.

Hugh Hoagland
ArcWear/e-Hazard
hugh@e-hazard.com

We had a technician who was kneeling down in front of a switchgear racking in a circuit breaker. The breaker indicator was in the open position and the technician did not use a meter to verify, there was never a need to verify this. The breaker was actually closed and a fault occurred when the breaker made contact. The blast threw our technician 10' back and into the outside wall of our switchgear room. The result was a broken collarbone, dislocated shoulder, and a cracked rib. However, the injuries were believed to be from contact with the wall and not the direct pressure of the blast. This was a 4160v gear with 22cal/cm^2 calculated incident energy.
Thanks