b. In any dwelling unit in a multiple dwelling erected prior to January 1, 1960 where a child of applicable age resides, the department shall conduct an inspection pursuant to subdivision a of this section no later than ten days after the department's receipt of a complaint describing peeling paint, or a deteriorated subsurface or underlying defect in the dwelling unit. The department shall make diligent efforts to ascertain whether a child of applicable age resides therein. Where the department attempts to perform an inspection of a dwelling unit within the time period required by this subdivision but is unable to gain access, the department shall be required to make a reasonable attempt to gain access to such dwelling unit within five days of such attempt. If the department is unable to gain access to that dwelling unit during this additional time period, the department shall provide written notice to the occupant of such dwelling unit that no further attempts at access shall be made unless a new complaint is submitted.