Where is my furnace vent located?

Author: Broderick Kautzer  |  Last update: Saturday, September 20, 2025

You might be wondering, “where is my furnace exhaust vent?” You can find the vent near the top of the furnace. This small duct connects to the outside of your house to vent fumes out. As winter approaches, many of us prepare our homes for the cold weather.

How do I find my furnace vent?

Your exterior furnace exhaust pipe is typically located on your home's sidewall, although it can be found on your home's roof in some cases. If you need help with locating it on the roof, please schedule an inspection with your nearest plumbing HVAC contractor.

How do I clear my furnace vent?

A small brush is usually enough to clear debris off the screen. For more stubborn buildup, you can use a shop vac, but that usually isn't necessary. To start, use a wire brush to remove: Leaves: Leaves that fall from deciduous trees or are blown by the wind can be sucked toward the intake vent and block it.

How do I find my furnace flue?

To inspect the vent piping of a modern, high-efficiency furnace, check the pipe that runs from the top of the device to outside the home high on an adjacent wall. The exhaust pipe should point upwards while the intake pipe points downwards and should be located at least five feet away.

Does my furnace vent through my chimney?

Furnaces with an AFUE of 90% and greater use special venting material such as PVC or stainless steel. A 90% furnace should never dump flue gases into a chimney. The installation instructions of these furnaces must be followed precisely for safe installation and operation.

National Homes’ #TipTuesdays: Quick Tips for Furnace Exterior Venting Maintenance

How do I find my flue pipe?

To find your boiler flue, first, identify where your boiler is installed. The flue typically exits directly through an external wall close to the boiler or extends upward through the roof. It will be a pipe or duct that leads from the top or side of the boiler to the outside of the property.

How do you know if your flue pipe is clogged?

Signs of Clogged Flues

If you see rust or water streaking on the vent, flue, or on your chimney, something may be blocking the flue. Moisture builds inside your furnace pipes when the air can't properly circulate, and this can result in rust. Soot around your furnace is also an indication of a problem.

Can I clean my own furnace vents?

Any vacuum will do the job, although we do advise that you use a heavier-duty vacuum if you got one handy. We recommend unscrewing the vents, vacuuming them off thoroughly and pushing the hose into the duct as far as it will allow in order to suck any loose dust or dirt.

What happens if the furnace vent is blocked?

Without proper ventilation, carbon monoxide can build up inside the house, which is incredibly dangerous as it can cause illness and potentially be fatal. As a result, many furnace manufacturers design their units so that they shut off automatically when the vent becomes blocked.

How do you check if a vent is blocked?

How To Know If Your Air Ducts Are Clogged
  1. One room in your house is hotter than all the others.
  2. Dirty air coming from vents.
  3. Unusual spikes in electric bills.
  4. Air is not blowing out of some vents in your house.
  5. Air coming from vents is warm.

How do you unclog a furnace?

Quick Highlights of Furnace Drain Issues and Fixes

Clear blockages using a wet/dry vacuum at trap inlet and outlet points to remove accumulated debris and sludge. Pour mixture of baking soda and vinegar through the drain system, followed by hot water to dissolve mineral deposits.

Do all furnaces have vents?

Every furnace needs a working ventilation system to expel odors, gases, particles, and even moisture. In order for a furnace to operate safely and efficiently, there must be a ventilation line (flue) to remove dangerous combustion gases from the home.

Where is the air vent located?

Vents, on the other hand, are the grilles or registers that attach to the ductwork and allow the air to enter each room as well as cycle back to the home's HVAC systems. Vents are typically located on the walls, floors, or ceilings of a home and can be opened or closed to regulate the flow of air.

What happens if the furnace air intake is blocked?

If the intake pipe becomes blocked, the heating system will likely stall and turn off as it can't pull in the required air for the combustion process. If the exhaust pipe becomes blocked, a safety mechanism should trip to prevent dangerous fumes from entering your home.

Does a gas furnace have to vent through the roof?

No, the roof is not the only place where a gas furnace can vent. The way a gas furnace is vented is determined by a number of variables, such as the kind of furnace, local building codes, and the unique features of your house.

How often should furnace vents be cleaned?

Experts advise having your air ducts cleaned every 2 to 3 years to prevent many maintenance and health problems before they start. However, homes with pets or children with allergies should have their air ducts professionally cleaned more frequently than the recommended average.

What does duct cleaning cost?

According to the Environmental Protection Agency, the average cost for properly cleaning an entire air duct system in an average-sized home ranges from $450 to $1,000.

How do I freshen my furnace vents?

How to Remove Odor from Air Ducts and Vents
  1. Air Filter Replacement: One of the simplest and most effective ways to get rid of bad smells is to replace the air filter. ...
  2. Vacuum the Vents: Use a vacuum cleaner to remove dust and debris from vents and registers.

Where is my furnace vent?

You might be wondering, “where is my furnace exhaust vent?” You can find the vent near the top of the furnace. This small duct connects to the outside of your house to vent fumes out. As winter approaches, many of us prepare our homes for the cold weather.

How much does it cost to replace a furnace flue pipe?

Flue Pipe: You'll pay $400 to $800 to replace a flue pipe, depending on its length and ease of access.

How to unclog furnace vent pipe?

If you think your exhaust flue has a clog, shut off your furnace and do the following:
  1. Clear away any snow blocking the vent by hand. Avoid using a snow blower to prevent damage to the vent.
  2. Remove any leaves, soot, or debris from the vent.
  3. Check the exhaust pipe for signs of damage.

Where is your flue located?

In most modern boiler applications, the flue passes horizontally through the wall the boiler is mounted on. Boilers located outside have a different flue arrangement that keeps them in line with regulations. Some boilers, especially oil burners, usually have their flue going vertically through the roof.

How do I find my vent pipe?

If you have a two-story home, go upstairs to locate the pipe. You can verify whether a pipe is a vent pipe by listening as someone flushes the toilet. If the pipe amplifies the flushing sound, it's likely the vent pipe. To find the plumbing vent on the roof, look for a pipe extending about six inches from the roof.

How to tell if your furnace is venting properly?

#1 Moisture and Condensation

Increased moisture within the home is a sign that your furnace venting isn't adequate. Without proper ventilation, fumes from the furnace leak into your home and cause condensation. This moisture is most notable in the morning and when you first turn on your heating unit.

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