This was a small coal burning Inglenook fireplace in a bedroom in a very old home. A 9x15 chimney ballloon was used to air seal the flue just above the firebox. This is a photo from the floor looking up the flue.
Combustion Appliance Zone Testing (CAZ) Made Easy (March 24, 2016)
-Adapting to the new BPI standard
-RESNET testing requirements
-NFPA testing requirements
-Best practices for best results