I used to sell woodstoves and have burned firewood for winter heating for over 48 years. It is VERY necessary to insure that there are no air leaks in the chimney. Very old stoves could tolerate draft leaks, but this new Englander is a different story. I had to create a seal for the clean out door and an additional unused opening into the chimney that was an alternate location for placing the woodstove. That alternate hole was not tightly sealed. Because of those poor original seals, the fire wanted to go out when the stove's glass door was closed. And I wish the air inlet control on the stove had a greater range, especially for starting fires.