Q: Can we expect some arc blast-rated PPE to arrive in the near future?
A: Neither e-Hazard nor ArcWear knows of anyone developing PPE for arc blast.
To look at arc blast and how it could relate to PPE, ArcWear and e-Hazard researched another paper this year measuring the force (N) on an impact plate from a door ejected by an arc blast. (This was presented at the 2019 IEEE Electrical Safety Workshop. It is available for purchase on the IEEE website.
From what we have seen in our last two papers, there will be few, if any, concussive injuries since the arc blast pressure is a function of containment AND current. A door ejected can be like a linebacker hitting you, and we would predict possible contusions. But the pressure when the door is open is VERY low – up to 18kA.
Small rooms could have issues as well. Equipment doors or parts blown off could deliver substantial blows. In accidents, we have seen workers knocked down and a few knocked out, but these are VERY rare.
When doors are open, arc blast is dispersed and would rarely contribute to injury. Of course, the work that has been done to date shows noise damage to ears is possible. Equipment doors hurting workers could occur (and have, in fact, already occurred).
PPE probably isn’t a solution for equipment with high blast pressures. Arc Resistant designs would be the best solution.
The NFPA 70E-2018 removed the 40 cal/cm2 cutoff for “arc blast” reasons. Arc blast isn’t a function of incident energy; it is a function of current and containment.
Maybe we will have a hazard assessment model some day, but we don’t for now. Open doors relieve the pressure but increase your incident energy. Working de-energized or wearing the proper PPE when that isn’t possible are your best options. BUT remember to “dress to test”.
We do talk about this issue in our Low Voltage NFPA 70E Classes.
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