chimney "chimney" includes any structure, opening, vent, flue, conduit, outlet or any structure constructed or arranged from or through which air impurities may be emitted, and any reference to a chimney of or used in connection with any premises, includes a reference to a chimney which serves the whole or a part of the premises though structurally separate from such premises or building thereon; PU(A) 280/1978 - ENVIRONMENTAL QUALITY (CLEAN AIR) REGULATIONS, 1978 2. Interpretation.