The world "common" means it occurs frequently. Frequently generally means more than once or twice a year in a population of 300m people. It also means that this type of death is universally known. For instance, motel pool drownings are common, and occur on a monthly basis. A simple Google search unearthed a large number of distinct listings for motel pool drownings, whereas a similar search for motel pool heater deaths unearthed the same incidents over and over.
Clearly you are not an epidemiologist. Using google search to determine incident rate is definitely not a way to determine relative rate.
FYI On average about 170 people die every year from carbon monoxide.