Question: I've got a reverse draft on a wood insert connected to a masonry chimney which causes a creosote smell when the insert is not in use. I believe this is mainly due to one of my central air's intakes being in the basement and causing a low pressure there (also just that the cold outside air is heavier then the warm inside air so tends to sink down the chimney). Will a top damper prevent the smell from coming into the house? Is there one which is OK to use with a wood insert (the ones I've seen say only for use with fireplace not wood inserts and gas logs)? Whats the issue with using a top-damper in combination with an insert? Answer: You are probably on to something when you suspect the problem is related to low pressure in the basement. The solution is not always so easy as determining the cause. Is your insert installed with a full liner to top? If not, that is likely contributing to the creosote smell. The smell can usually be minimized by a rotary or chemical cleaning of the entire fireplace and chimney flue, followed by a full reline with a high quality insulated liner system and block-off plates at both the top an bottom, followed by correct burning procedures to eliminate creosote creation (You may need new stove for this depending on circumstances). A top damper has proven to be helpful when used with open fireplaces. Glass doors also help sometimes. But the best solution with an insert is a full liner and block-off system. The issue with lock-tops and stoves is that stoves burn much longer than open fireplaces and it is hard to ensure that there is no combustion taking place. In an open fireplace you can snuff the fire with an extinguisher. Once the fire is completely out you can lock the damper. Not a good idea with a stove/insert.