An apparatus including a housing defining a heating process chamber. The housing has an opening communicating the process chamber to the ambient atmosphere. A burner is included that fires into a combustion chamber to heat gas. Also included is a collector structure located outside the opening. The collector structure is configured to collect air and exfiltrated gas from an outside area adjacent to the opening. The apparatus also includes a duct structure communicating the collector structure with the burner so as to supply the collected air and exfiltrated gas to the burner and thereby to supply combustion oxidant to the burner.