First off it's a "carbon monoxide", CO, detector not dioxide, CO2.
It may be the stink when using the gas furnace the first time of the season or the furnace fan running pulled the battery voltage down too low. That detector is very sensitive to low voltage as well.
If neither of these it could be a bad detector. Remove it & check date on the back, they're only good for about 5 years. Yours is already at least 3 & depending how long it was on the shelf at the factory it could be nearly 5 by now.
Danny & Linda
Sold my '13 Redwood 36FB
Currently rv & truckless