staircases, tunnels, stairways, doorways, cavelike, alcoves, entryways, alleyways, archways, breezeways, walkways, entrances, caverns, vestibules, courtyards, corridors, warren, labyrinths, porticoes, sarcophaguses, crevices, spiral staircase, catacombs, caves, pathways, egress, ledges, vents, ventilation, alleys, drainpipes, abysses, hallways, airlocks, crevasses, inlets, compartments, spiracles, maze, stalactites, naves, spaces, dungeons, hatchways, grottos, chasms, passages, skylit, ducts, wormholes, bronchioles, portholes, lazarette, trabeculae, clerestories, anterooms, alveoli, rills, wadis, louvres, egresses, promontories, rockwork, blowholes, walls, tracheae, harborage, lintels, apertures, arches, bronchi, gargoyles, canals, bronchial tubes, crenellations, rabbit warren, entranceway, palisades, stairwell, cavity, colonnades, quoins, claustrophobia, hoistway, abyssal, promenade deck, nooks, balconies, meshwork, chimneys, ductwork, antechamber, atriums, rathskeller, bowels, skylights, pilasters, crossbeams, obstructions, transoms, capillaries, boardwalks, passageway, galleries, conduits, burrows, corridor, openings, troughs, tunnel, watercourses

air cell, air sac, alveolus, atrium, bronchodilator, chronic pyelonephritis, laryngotracheobronchitis