Shop with confidence on eBay! How the H Cowl Chimney Terminal Works In normal or still air weather conditions the hot gases and smoke pass up the chimney and exit out of the top of both o of the vertical tubes. £39.99. Whether you are looking for a Chimney Cap, an Anti Downdraught Cowl or Spinner - we have it. Bucks, A reclaimed chimney cowl Size (H,L,W) – 250mm x 295mm x 245mm / 9 3/4″ x 11 3/4″ x 9… View details; Sold RECLAIMED TERRACOTTA CHIMNEY POT.