Radon is an odorless, colorless, radioactive, and highly-carcinogenic gas that seeps out of the Earth. Illinois landlords are not required to conduct radon testing, although landlords with knowledge of a radon hazard are required to disclose the existence of that hazard to all prospective tenants seeking to rent on the first or second floors above ground level. Our radon disclosure form is for Chicago apartment rental landlords obligated to make a disclosure. Landlords who lack knowledge of a radon hazard need not complete the form, even though it offers Chicago apartment landlords the opportunity to disclose the absence of a known hazard. Landlords of Chicago rentals overly zealous about paperwork and compliance issues may feel compelled to complete the form as a matter of routine, but a failure to do so will entail no adverse consequences in the absence of known hazard.