Airtight stoves use gaskets on their doors, which need to be checked and replaced from time to time. To inspect the gasket while the stove is cold, place a dollar bill halfway in the door opening and close and latch the door. If you’re able to pull the bill out from between the door and the stove with no resistance, the gasket is worn and should be replaced.
You can find complete replacement door gasket kits for Dwarf stoves here.
If a stove gasket is still in good condition but starts to detach, it can sometimes be reattached to the stove with stove gasket cement. Clean off as much of the old gasket cement as possible from both surfaces. Then, dampen the area with water and apply a thin layer of cement to the gasket channel. Press the gasket firmly into the cement, being sure to keep the gasket material in a relaxed state, avoiding stretching it at the corners. Close the door to ensure the gasket is set in place, then allow to air dry for 1 hour with the door open. Fire the stove within 30 days and heat to 500 degrees F to cure the cement.