The State of Illinois Public Act 094-0741 requires that a carbon monoxide detector be installed within 15 feet of all sleeping rooms of all dwelling units. This may require multiple detectors for homes or apartments.
The law applies to single-family homes, duplexes, townhouses, apartments, hotels, and motels.
Various types of detectors may be used:
Plug in with battery backup
Direct-wired to the building electrical system with battery backup
There are some combination smoke and carbon monoxide detectors that may be used. A different tone is required for smoke detection and carbon monoxide detection. If using a combination type detector, check the product literature for compatibility with existing detectors.
The homeowner or landlord is responsible for the installation of the detector. In rental units, tenants are responsible for keeping fresh batteries in the detectors. If the owner is going to have hardwired detectors installed, an electrical permit will be required.
There are penalties in the act for noncompliance. A copy of the act is available here.