Illinois Statutes Chapter 430. Public Safety § 135/20. Exemptions

(1) A residential unit in a building that: (i) does not rely on combustion of fossil fuel for heat, ventilation, or hot water; (ii) is not connected in any way to a garage; and (iii) is not sufficiently close to any ventilated source of carbon monoxide, as determined by the local building commissioner, to receive carbon monoxide from that source.

(2) A residential unit that is not sufficiently close to any source of carbon monoxide so as to be at risk of receiving carbon monoxide from that source, as determined by the local building commissioner.