A gas heater with a closed combustion chamber has the following options for exhaust gas ejection / air intake for combustion:

Connecting the  pipe in pipe and the pipe connecting the discharge of exhaust gases (60 mm in diameter models  GH0618  and  GH0825 ) is located inside the air intake pipe. Example of flue gas outlet / combustion air inlet.

Connecting the exhaust gas outlet  to one pipe and leading it outside. Air intake for combustion from inside the hall. With this method of connecting the combustion air, the heater efficiency is significantly increased, because the air intended for combustion will have a higher temperature.

Connecting the flue gas  pipe with one flue pipe and connecting the combustion air with the other pipe.

The exhaust outlets should be made of stainless steel resistant to the effects of exhaust gases coming from the gas heater combustion chamber. The exhaust pipes should be well sealed so that the exhaust gases do not remain inside the room. The length of the flue gas pipe must not exceed the maximum length specified in the operating and installation manual.