How many people die a year from not having a carbon monoxide alarm installed?

Someone left the gas running on a gas stove today and it took us several hours to figure out what was happening. I realized how hard it can be to detect and how important it is to have an alarm installed. Not sure how long it would have taken to get serious but I might have blown myself up if i had lit the stove. It makes me wonder how long it would have taken to become more serious assuming no spark or flame was lit but just from the exposure to the gas itself.