(1) two or more apartments are combined creating larger residential units, and

(2) the total legal number of families within the building is being decreased, and

(3) the bulk of the buildings is not being increased These exceptions shall not be deemed to relieve any owner from the obligation to make every alteration required in any old-law tenement or other multiple dwelling in compliance with the applicable provisions of this chapter. 2. Except as above provided, no dwelling constructed as or altered or converted into a multiple dwelling after April eighteenth, nineteen hundred twenty-nine, shall be occupied in whole or in part until the issuance of a certificate of compliance or occupancy. 3. Such certificate shall be issued within ten days after written application therefor if the dwelling shall be entitled thereto. The department shall, on request of the owner or of his certified agent, issue a certificate of compliance or occupancy for any existing multiple dwelling not requiring such certificate, provided that, after an inspection by the department, no violations are found against such dwelling. 4. The head of the department may, on the request of the owner or his certified agent, issue a temporary certificate of compliance or occupancy for a multiple dwelling or a section or a part thereof for a period of ninety days or less, provided that such certificate shall bear the endorsement that the dwelling has been inspected by the department and complies with all the requirements of this chapter, and that such temporary occupancy will not jeopardize life, health or property. Such temporary certificate may be renewed at the discretion of the head of the department for similar periods but shall not extend, together with such renewals, beyond a total period of two years from the date of its original issuance. 5. A certificate, a record in the department, or a statement signed by the head of the department that a certificate has been issued, may be relied upon by every person who in good faith purchases a multiple dwelling or who in good faith lends money upon the security of a mortgage covering such a dwelling. Whenever any person has so relied upon such a certificate, no claim that such dwelling had not, prior to the issuance of such certificate, conformed in all respects to the provisions of this chapter shall be made against such person or against the interest of such person in a multiple dwelling to which such a certificate applies or concerning which such a statement has been issued. 6. Notwithstanding any general or local law to the contrary, a certificate issued for any multiple dwelling organized pursuant to the provisions of article nine-B of the real property law, shall be deemed issued for each dwelling unit contained within such multiple dwelling in full compliance with the requirements of this section.