Hey, I was wondering when I should replace my helmet due to safety. I took a really bad fall 1 month ago skiing the glacier park. I lose balance on a flat down box and slammed my head right on the edge of the box, which caused me to have a little "blackout?" for like 5 secs. i did have a terrible head ache the rest of the day.Is my helmet unsafe now? I heard something about 1 big hit and it should be replaced