55 Pa. Code § 3290.70 – Ventilation.

(a) Natural or mechanical ventilation shall be provided in child care spaces.
(b) Windows or doors used for ventilation shall be screened when open.
(c) Screens shall be in good repair.
(d) Windows or doors above the ground floor that open directly to the outdoors and are accessible to children shall be constructed, modified or adapted to limit the openings to 6 or fewer inches.

This section cited in 55 Pa. Code § 3290.25 (relating to waivers).