Note: Whenever a dwelling is occupied by less than six families and where, within a portion of one or more of these apartments a professional service (medicine, dentistry, engineering, etc.) or a nonprofessional service (dressmaking, etc.) is being rendered and such remaining portion of the apartment(s) is used as an abode of the individual rendering the service, the boiler located within the dwelling shall be deemed to be exempt. This exception shall not apply when such services are separate and apart from the apartment proper wherein the individual rendering the services resides, such as a store or separate apartment within the dwelling.
N.Y. Comp. Codes R. & Regs. Tit. 12 §§ 4-1.3