N.Y.C. Admin. Code § 27-538: § 27-538 Vertical exits.

Stairs, escalators and ramps shall comply with all of the requirements of subchapter six of this chapter, except as modified below:

(a) Capacity. The capacity of stairs, escalators or ramps shall be as listed in table 8-1.

(b) Width. The minimum width of stairs shall be at least forty-four inches, except that where the total occupant load is not more than permitted for one unit of exit width, the minimum width may be thirty-six inches.

(c) Unenclosed vertical exits. Vertical exits leading directly from one safe area to another, or leading from a safe area directly to an open exterior space, need not be enclosed.

(d) Ramp slope. Ramps serving as vertical exits shall not have a slope greater than one in ten.