; (D) have appropriate heating and ventilation systems; (E) not deprive prisoners or staff of natural light, of light sufficient to permit reading throughout prisoners’ housing areas, and of reasonable darkness during the sleeping hours; (F) be free from tobacco smoke and excessive noise; (G) allow unrestricted access for prisoners to potable drinking water and to adequate, clean, reasonably private, and functioning toilets and washbasins; and (H) comply with health, safety, and building codes, subject to regular inspection; (16) all Bureau of Prisons facility housing conditions shall— (A) include living quarters of adequate size, with single-occupancy cells as the preferred form of housing, but facilities that must use multiple-person living quarters should provide sufficient staffing, supervision, and personal space to ensure safety for persons and security for their belongings, and to ensure that all living quarters and personal hygiene areas are designed to facilitate adequate and appropriate supervision of incarcerated persons and to allow such persons privacy consistent with their security classification; (B) at a minimum, include a bed and mattress off the floor for each incarcerated person, a writing area and seating, an individual secure storage compartment sufficient in size to hold personal belongings and legal papers, a source of natural light, and light sufficient to permit reading; and (C) sufficient access to showers at an appropriate temperature to enable each incarcerated person to shower as frequently as necessary, and allowing for gender appropriate separation, to maintain general hygiene; (17) living quarters and associated common areas shall be maintained in a sanitary condition