. . . . . "ing fixtures in the dwelling unit or used by the tenants as clean as their condition permits; (e) use in a reasonable manner all electrical, plumbing, sanitary, heating, ventilating, air-conditioning and other facilities and appliances, including elevators, in the premises; (f) not deliberately or negligently destroy, deface, damage, impair or remove any part of the premises or knowingly permit an" . .