wherein the break is in air at atmospheric pressure, e.g. in open air

Full Title

High-tension or heavy-current switches with arc-extinguishing or arc-preventing means > Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid > having stationary parts for directing the flow of arc-extinguishing fluid, e.g. arc-extinguishing chamber > wherein the break is in air at atmospheric pressure, e.g. in open air