Chapter 123 of the Acts of 2005
New and existing single- and multi-family dwellings, boarding houses, hotels, motels, dormitories, apartments, and adult and child care facilities are required to be equipped with CO detection devices, in conformance with requirements of the Board of Fire Prevention Regulations. (Effective dates: March 31, 2006 for battery-powered; January 1, 2007 for hard-wired)

General Laws of Massachusetts Ch. 143 Section 26F1/2:
Every dwelling, building or structure, including those owned or operated by the commonwealth, occupied in whole or in part for residential purposes, that: (1) contains fossil-fuel burning equipment including, but not limited to, a furnace, boiler, water heater, fireplace or any other apparatus, appliance or device that burns fossil fuel; or (2) incorporates enclosed parking within its structure shall be equipped by the owner with working, approved carbon monoxide alarms in conformance with the requirements of the board of fire prevention regulations;