Unfortunately, the contractor did not install a duct and bring it to the exterior, he just buried it in the fiberglas which has been filtering the exhaust for a few years. Note the rust from condensation on the housing.
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