inspection of any treated unit by a qualified inspector. If the qualified inspector determines that any such unit is not infested with bed bugs, the qualified inspector shall provide the landlord with a written certification of such determination. If the qualified inspector determines that any such unit is infested with bed bugs, the landlord shall, not later than five business days after the date of such inspection, retain the services of a pest control agent. Except as otherwise provided in this section, the landlord shall be responsible for all costs associated with inspection for and treatment of a bed bug infestation. Nothing in this section shall be construed to preclude a tenant from contacting any agency at any time concerning an infestation of bed bugs.