Smoking isn't dangerous while chainsawing. Also although it looks absurd, it's almost completely safe to start a chainsaw like that (although the picture is presumably posed). If the chain brake is on the chain won't turn. If the chain brake is off the chain still won't turn while the engine idles, you have to depress the palm button and pull the trigger. Maybe the saw could be faulty though or you somehow accidentally depress the palm button and pull the trigger while holding it between your legs so there is a very small but unnecessary risk involved.