Fire Code New York State §610: 
CO detectors are required in multiple occupancies, including, but not limited to, hotels/motels; apartment buildings; dormitories; adult/child care facilities; assisted living facilities; alcohol/drug centers; convalescent facilities; day care facilities; and certain educational occupancies. (Effective date: December 28, 2010)

Part 1228.4 of Title 19 NYCRR: 
CO detectors are required in all new and existing “commercial” buildings, including K-12 schools. (Effective date: July 27, 2015 for new buildings and July 27, 2016 for existing buildings).