As of June 2015, all apartment units and multifamily dwellings in Pennsylvania are required by law to include carbon monoxide alarms within the vicinity of the units' bedrooms. On December 18, 2013, Governor Tom Corbett signed Act Number 121, which requires any such facilities that use fossil fuel-burning appliances or have an attached garage, to install a centrally located and approved carbon monoxide alarm near bedrooms and the fossil fuel-burning appliance. The Act became effective immediately and allows 18 months for owners and management to put the proper devices in place. The Act lists owner responsibilities including maintenance and repair requirements.

The Pennsylvania Apartment Association was instrumental in having occupant responsibilities included in the Act as well. These responsibilities put the onus of device upkeep and battery replacement on rental residents during their occupancies. Residents must also replace the actual device if it is lost, stolen, removed, or found to be broken, during their occupancies. Additionally, residents must notify the owner in writing if the device is found to be insufficient or defective. The Act states the term "approved carbon monoxide alarm" as:

1. A single or multiple station carbon monoxide alarm listed as complying with the Approved American National Standard for Single and Multiple Station Carbon Monoxide Alarms (ANSI/UL2034) or a carbon monoxide detector listed as complying with the Approved American National Standard for Gas and Vapor Detectors and Sensors (ANSI/UL2075).

2. A device that may be combined with a smoke alarm or smoke detector must comply with either of the following:

The Approved American National Standard for Single and Multiple Station Carbon Monoxide Alarms (ANSI/UL2034) for carbon monoxide alarms and the Approved American National Standard for Single and Multiple Station Smoke Alarms (ANSI/UL217) for smoke alarms.

The Approved American National Standard for Gas and Vapor Detectors and Sensors (ANSI/UL2075) for carbon monoxide detectors and the Approved American National Standard for Safety smoke detectors for fire alarm systems (ANSI/UL268) for smoke detectors. If combined, it must emit an alarm in a manner that clearly differentiates between detecting the presence of carbon monoxide and the presence of smoke. 3. A carbon monoxide detection system that includes carbon monoxide detectors and audible notification appliances that are installed and maintained in accordance with the National Fire Alarm and Signaling Code (NFPA 72) and the Standard for the Installation of Carbon Monoxide (CO) Detection and Warning Equipment (NFPA 720) and are in compliance with the Approved American National Standard for Gas and Vapor Detectors and Sensors (ANSI/UL2075).