Hi, The Apollo I have is linked with an Intelli-Vent White Rodgers. It's install dates March 2008. I called to have it checked after smelling a gas smell and co was also detected. Otherwise it works beautifully. 2 GVAC companies do not seem to know what to do with it. There is a bird living in the Intake pipe about 6-9 feet in.. $189 later plumber with camera,(after the initial $120 HVAC call/diagnosis visit), wants to cut a hole in my ceiling and replace the pipe, (since he "does not have something to blow it out"). Of course this needs to be addressed,but from video, twigs not fully,maybe half?, obstructing- could that be a reason for it not exhausting properly?? Also, HVAC Sean stated that the pipes were not caulked.. and he sawed the exhaust PVC off to check for obstruction. Could he have just disassembled?? I'm not sure where the strongest co reading was, aside from near the top of the closet. Lastly, do you have any thoughts that might help me- the unit is unplugged. gas turned off. Thank You, I look forward to your reply!