The OH Cowl so remarkably successful and so completely reliable that should cure the downdraught in any chimney, however bad.
H Cowls available below - Galvanised Traditional H Cowl Stainless Steel Traditional H Cowl Stainless Steel Gas Traditional H Cowl Aluminium Gas Traditional H CowlL
How the Traditional OH Chimney Cowl Works
Any wind blowing up or down the two open-ended air shafts A or B is intensified where it passes the projections of the horizontal flue C, and so draws the smoke and fumes out from the chimney.
The main flue D projects into the horizontal flue C, thus there are three ejectors acting simultaneously and drawing out the smoke and fumes, whether the wind blows up or down the air shafts. So powerful is this action that gusts of wind blowing through the air shafts produce an up-draught equal to about 30% of the velocity of the gusts. In normal weather, the O.H. Cowl possessing four outlets to the atmosphere improves any sluggish updraught.