N.Y.C. Admin. Code § 27-416: § 27-416 Radiation machines.

Radiation machines or particle accelerators, linear accelerators, cyclotrons, synchrotons, betatrons, or bevatrons shall be located only in buildings of noncombustible group I construction; however, this requirement shall not apply to conventional medical, dental, research, or industrial x-ray machines of less than one million volt capacity.