a-1. No later than the earliest of August 9, 2025, one year after a child of applicable age comes to reside in a dwelling unit subject to the requirements of subdivision a of this section, or the issuance of an order by the department of health and mental hygiene as required by such order, one investigation for the presence of lead-based paint undertaken pursuant to subdivision a of this section shall be performed by a person who (i) is not the owner or the agent of the owner or any contractor hired to perform work related to the remediation of lead-based paint hazards, and (ii) is certified as an inspector or risk assessor pursuant to section 745.226 of title 40 of the code of federal regulations. Such inspection shall consist of the use of an x-ray fluorescence analyzer on all types of surfaces in accordance with the procedures described in chapter 7 of the United States department of housing and urban development guidelines for the evaluation and control of lead-based paint hazards in housing, including on chewable surfaces, friction surfaces, and impact surfaces, to determine whether lead-based paint is present, and where such paint is located, in such dwelling unit and in the common areas of such multiple dwelling. Provided, however, that the investigation specified by this subdivision shall not be required if an investigation that complies with the requirements of this subdivision was previously completed and the owner retains records of such investigation, or if the dwelling unit has an exemption from the presumption of lead paint, as provided in subdivision b of section 27-2056.5 of this article.