Yeah unfortunately the "rule" I've always been told and that I've always used (at least in mountain biking and BMX racing) is one hit on a helmet. One of the guys I raced with actually sent a helmet in to the manufacturer (I think it was Troy Lee Designs but not 100% on that) to get it analyzed ($450 helmet crashed the first lap on the track with it
) hoping they would tell him it's safe to use. It had a scratch similar to your picture. The analysis came back that the outer shell had microscopic spiderweb cracks throughout and the inner core had dented and collapsed enough that if there was another impact on that spot, the shock would transfer straight into the head instead of being displaced by the core foam.
Glad you're OK though. I got sprinkled on for the first time today and got my ass home ASAP!
Glad you're OK though. I got sprinkled on for the first time today and got my ass home ASAP!