<s>[INST] I m very worried because I held my breath while walking for about 40 seconds (I was trying to avoid breathing in noxious fumes from a new stretch of tarmac on my way home) and experienced some dizziness. Did I deprive my brain of oxygen enough to damage any brain cells? This seems like a rather inane question, I know, but I have pretty severe OCD and I can t stop worrying about it. [/INST] no before damage occurs you will pass out.  the brain preserves function by shunting blood to places where it's needed </s>