Yeah ever since I read that, I crack the visor or open it when i'm sitting still. And for opening the visor in accidents, I'm no expert but I believe it would

Yeah ever since I read that, I crack the visor or open it when i'm sitting still. And for opening the visor in accidents, I'm no expert but I believe it would be safe to do if you can do it without moving their head. IIRC the reason you don't want to take off the helmet is because you could strain their neck doing so. If you could move the visor without moving their head, it probably won't hurt, but at the same time I'm not sure if I'd worry about that in this kind of situation (having seen a motorcycle accident, the amount of co2 that person is breathing is, to me anyway, far down the list behind "call 911" and "make sure they don't get run over again"). I think the findings were more to try and get the helmet manufacturers to design systems which let more air in during an accident or when stopped. [1] has the study I remember reading about, and it turns out that according to their abstract, opening the visor at a stop has little effect on average! So maybe my behaviour of cracking the visor isn't doing much... [1] https://www.ncbi.nlm.nih.gov/pubmed/15893291 https://www.ncbi.nlm.nih.gov/pubmed/15893291