Smoke alarms are required in every bedroom, outside each sleeping area, and on every level of the home including the basement.
One CO alarm or combination CO/smoke alarm within 15 feet of each bedroom entry door
One CO alarm or combination CO/smoke alarm on each level of a multi-level dwelling unit including the basement.
One CO alarm or combination CO/smoke alarm within each bedroom containing a fuel-burning appliance
For more information: https://www.denvergov.org/content/dam/denvergov/Portals/678/documents/safety-information/Residential_Fire_Safety_Handout.pdf