Chicago Residential Landlord & Tenant Ordinance
Section 5-12-050 Landlord's Right of Access
A tenant shall not unreasonably withhold consent to the landlord to enter the dwelling unit:
(a) To make necessary or agreed repairs, decorations, alterations or improvements;
(b) To supply necessary or agreed services;
(c) To conduct inspections authorized or required by any government agency;
(d) To exhibit the dwelling unit to prospective or actual purchasers, mortgagees, workmen or contractors;
(e) To exhibit the dwelling unit to prospective tenants 60 days or less prior to the expiration of the existing rental agreement;
(f) For practical necessity where repairs or maintenance elsewhere in the building unexpectedly require such access;
(g) To determine a tenant's compliance with provisions in the rental agreement; and
(h) In case of emergency.
The landlord shall not abuse the right of access or use it to harass the tenant. Except in cases where access is authorized by subsection (f) or (h) of this section, the landlord shall give the tenant notice of the landlord's intent to enter of no less than two days. Such notice shall be provided directly to each dwelling unit by mail, telephone, written notice to the dwelling unit, or by other reasonable means designed in good faith to provide notice to the tenant.
If access is required because of repair work for common facilities or other apartments, a general notice may be given by the landlord to all potentially affected tenants that entry may be required. In cases where access is authorized by subsection (f) or (h) of this section, the landlord may enter the dwelling unit without notice or consent of the tenant. The landlord shall give the tenant notice of such entry within two days after such entry.
The landlord may enter only at reasonable times except in case of an emergency. An entry between 8:00 a.m. and 8:00 p.m. or at any other time expressly requested by the tenant shall be presumed reasonable.
Under this section of the RLTO Tenants are entitled to advance notice from their landlord of at least "2-days." The notice does not have to be in writing, and could be a phone call or note under the door.
The only exceptions are under subsections (h), in case of an emergency, and (f), if repairs elsewhere in building unexpectedly require access.
Also, advance notice aside, the landlord is not supposed to enter outside the hours of 8am through 8pm, unless the landlord and tenant have agreed to something outside that range.
Look at RLTO 060 to see what happens if the landlord makes an entry to show the apartment without giving at least 48-hours' notice... damages for the tenant equal to one-month's rent.