Oregon Revised Statutes Property Rights and Transactions § 90.316

(1) Unless a dwelling unit contains one or more properly functioning carbon monoxide alarms installed in compliance with State Fire Marshal rules and with any applicable requirements of the state building code when a tenant takes possession of the dwelling unit, a landlord may not enter into a rental agreement creating a new tenancy in the dwelling unit if the dwelling unit:

(2) The landlord shall provide a new tenant with alarm testing instructions as described in ORS 90.317.

(3) If a carbon monoxide alarm is battery-operated or has a battery-operated backup system, the landlord shall supply working batteries for the alarm at the beginning of a new tenancy.