I just went through level 1 contamination with MK4 OC 10%. Needless to say it sucked but it didn't prevent me from making it through the course. The hardest time i had during the course was seeing where i was going. Afterward I was more irritated that i couldn't keep my eyes open than i was with the burning. It was about three hours ago and i can still feel the irritation around my eyes mostly.
It was fun to be able to kick the crap out of someone in a skittle suit though, it's been a while since i had access to gear like that.