New York Codes, Rules and Regulations
Title 21 - Miscellaneous
Chapter XXIV - The Port Authority Of New York And New Jersey
Subchapter E - World Trade Center
Part 1290 - World Trade Center
Section 1290.16 - Obstruction light, air, heat, etc. passage prohibited

No person shall obstruct or permit the obstruction of light, air or passage in the World Trade Center, or cover or obstruct any elements of the heating, ventilating or air cooling systems therein. In addition no person shall place any window coverings including without limitation thereto, curtains, blinds, shades, draperies or screens on any exterior window, without the prior written consent of the manager of the World Trade Center, but all occupants of space shall provide and install, at their expense, such draperies as the Port Authority may in its discretion require or approve, and all occupants of space shall keep the draperies closed whenever the sun is shining on the windows.