It could be that the flue requires sweeping or that the flue is obstructed in some way, possibly by a nest or fallen leaves.
The fireplace size may not be compatible with the cross sectional area size and height of the chimney flue or the grate is too low or too far forward in relation to the fireplace recess.
The chimney stack may terminate in a high pressure zone causing down draught or there may be a wind derived down draught.
The chimney may be cold and damp causing lack of flue up draught or the ventilation provided may be insufficient.
We can come to your property and do a site survey to determine why your chimney isn’t working as it should. We will give you some advice and let you know of potential costs and duration of work required to make your chimney safe again.