34 Pa. Code § 41.164 – Maintenance.

(a) Linens shall be changed weekly or for each new occupant.
(b) During the season when flies are prevalent, all openings into outer air shall be screened and doors shall be self-closing.
(c) The employer shall keep the entire building in repair, including the plumbing, lighting, heating, and ventilating system. The employer shall also keep the entire building in a clean condition, free from any accumulation of dirt, garbage or other refuse matter.

This section cited in 34 Pa. Code § 41.182 (relating to ventilation).