Never seen “screening” in the heat exchanger flame port before,… was wondering if its a new thing or should not be there. Brand new house, brand new gas furnance. They glow bright orange with the flame shooting through them… any purpose for this?? Anyone? Thanks.


Never seen that, Call the manufacturer

I ain’t never saw it, too…do like the man say–call the manufacturer.

Anyone else know??

Perhaps they were suppose to be removed before final installation and start up.

Erol Kartal
Pro Inspect

I see them all the time here in San Diego. I had one HVAC tech tell me that they are there to keep critters from making homes in those nice tubes since, in many areas here, we don’t use our furnaces that much. Considering some of the critters that I’ve seen in attics (where about half of our furnaces are), it sounded as reasonable as anything else.



I’m thinking the manufacturer has done this to be more restrictive [chamber] to natural flow of products,in order to extract more heat from products.

Is the furnace you inspected power vented,or induced draft?Resticting products usually works best with these two systems.

Hi Russel:D :smiley:

Yes it was an induced draft furnace… this and the “critter” comment by Russel makes sence but which is correct??? Thanks for the help guys.


Take your pick,the critter reason that Russel gave is plausible but not likely.Anything that is in the chamber will disintegrate and go up the vent.

Read all of my post, though.

Many of us here in some San Diego areas rarely use our furnaces. I’ve been in my home here for four years and have used the furnace maybe a total of 10 times, so it is plausible for rodents that get into my attic to get into the furnace and make their home for several months, raise their young, and get out before I fire up the furnace.

Now, Toronto, well, that’s a different story.

Peter’s over in Olympia, Washington, so I think it is not only plausible for his area, but possibly likely.


Russel, did you happen to notice in the posted photos that the screen does not cover the tube all the way?
How would this funtion as a pest guard?

Screens get damaged. Virtually anything can get damaged during installation and use.

Really? ALL three of them?


Nice to have you back!! I’m just guessing here about the screen, I have never seen this.Usually manufactures control restrictive flow of the products with the shape of the chamber,But I don’t think the manufacturer cares about rodents,or critters.Unless the installer did this [on his own] from his years of experience!!!


If the screens are for rodents and I don’t think they are you are right all three,Not likely!


All I’m saying is that I see them quite often, specifically in furnaces located in attics. And I’m simply relaying what an HVAC guy told me when we both were at an inspection together during one of my TECH inspections.

It is even possible for the installer to attempt to take them out, not knowing that they actually might supposed to be there. I suppose it’s even possible that the HVAC guy installed them, so maybe that guy didn’t install them adequately. I didn’t ask my HVAC guy if they came like that from the manufacturer or if the HVAC guys were installing them. Maybe that Olympia HVAC guy is a transplant from Southern California, having moved to Olympia since it’s less expensive to live there.

I have no intention of getting into an argument one way or the other since I have to get out of here today. I’m just saying that I found my HVAC guy’s explanation to be plausible based on conditions here in San Diego.




These are pretty common on newer units, although I don’t know the reason. . .