N.Y.C. Admin. Code § 27-249: § 27-249 Classification.

Buildings and spaces shall be classified in the industrial occupancy group when they are used for fabricating, assembling, manufacturing, or processing products, materials, or energy, except that when any products or materials, or other products or materials used in their manufacture are highly combustible, flammable, or explosive, the occupancy shall meet the requirements for high hazard occupancies when the latter are more restrictive than the corresponding requirements for the industrial classification. The industrial occupancy group consists of sub groups D-1 and D-2.