Most homeowner furnace checks stop at the filter and the thermostat. On a gas furnace with a sealed combustion system, that misses part of the appliance. The intake and exhaust pipes run through a wall or roof and end outdoors, and those terminations are where snow, ice, leaves, and wind do their work. A blocked termination can shut the burner down, and it is a safety issue, not just a comfort one. Walking the outside of the house takes about ten minutes and needs no meter.
What to Walk and Look For
Bring a flashlight and a phone camera. Start with the intake, the pipe that brings combustion air in. Check that it is still attached at every joint, that it is not cracked or sagging, and that nothing sits in the opening. Then check the exhaust, which is often the taller or more visible pipe. Look for ice buildup, bird nests, and debris collected around the end. Confirm that both ends face the direction the install manual describes and that neither is buried in a drift or tucked behind a shrub.
Take photos from the same spot each time. A dated picture is the only reliable record of whether a pipe has moved. Pipe supports, couplings, and the bend near the wall are the places where slow movement shows first. When you judge clearance to a window, grade, or air intake for another appliance, use the clearance table in the install manual, not memory.
Ice Is a Hand Job, Not a Hammer Job
If ice has built up at a termination, do not chip it with a screwdriver, shovel, or any metal tool. Plastic pipe cracks, and a cracked intake or exhaust is worse than a clogged one. Do not pour boiling water on it either. Keep the area around the outdoor ends clear of snow after storms, never store anything against the pipe, and call the furnace service provider to clear heavy ice and check the appliance.
Roof Penetrations and the Crew You Call
If the vent passes through the roof, the flashing and the seal around the pipe matter as much as the pipe itself. A slipped collar or a failed boot lets water into the attic, and that water usually shows up later as stained drywall rather than as a furnace fault. Checking this from the ground has limits. If you see staining, loose flashing, or a pipe that has lifted, bring in a roofing contractor such as Keys Roofing before the next storm season. Ask them to coordinate with the furnace service company so the seal is repaired without bending the pipe out of alignment.
New Equipment Still Needs the Same Walk
New furnace purchases are where this check gets skipped. ACHR News reported on Lennox residential HVAC revenue in the third quarter, and its summary points to "Homeowner affordability concerns persist" as the company adjusts pricing and prepares lower-priced equipment options. A lower tier is still a furnace with a venting spec, and that spec lives in the install manual, not the brochure. Compare the termination layout in the manual against what is already on your wall or roof, and ask the installer to confirm in writing which existing pipe will be reused.
Policy Talk Does Not Move a Pipe
ACHR News also covered the trade's policy agenda in a piece on HVAC policy work regardless of the midterm outcome. Its summary lists rising material costs, proposed apprenticeship changes, and "federal funding uncertainty" as SMACNA pushes for indoor air quality legislation. None of that changes the walk around your house. A contractor working through tighter material costs has less slack for a rushed call, which makes your own check and dated photos more useful.
The Short Checklist
Keep this list in your phone: intake and exhaust both attached, no cracks or sagging, no ice, no nests or debris, no snow drift over either end, flashing and seals intact where the pipe leaves the roof, and dated photos to compare next season. Write the findings down next to the nameplate data. If anything looks off, call the furnace service provider first, and do not run the appliance while you wait on a suspected blockage.