If the problem (smoke or fumes coming out the fireplace or stove) occurs ONLY IN WINDY conditions then THIS IS A DOWNDRAUGHT. The anti down draught cowls to use are: A) Static Cowl if your problem is not severe (found here). B) A Spinner Cowl if the your problem is severe (found here).
If the problem (smoke or fumes coming out the fireplace or stove) occurs when there is LITTLE or NO WIND then this is not a downdraught. This is a LACK OF DRAUGHT.
No anti down draught cowl will fix a lack of draught there is only ONE cowl to fix a LACK OF DRAUGHT and that is an ELECTRIC cowl called the SUPER C.
If the Chimney Problem is heat loss, over performance of chimney, excessive fuel consumption or exterior noise in the chimney, then the cowl you need to fix this is the CHIMNEY CONTROL (found here).
If the problem is rain or birds nesting then the cowl you need is the Anti Bird/Anti Rain cowl (found here).
Please read our leaflets on each individual cowl which can be found on their product pages.