Chimney Troubleshooting Guide for Consumers (2020)

Opening Too Large

Everybody loves a nice large fire, but a very common problem is when the fireplace opening is too large. 

If the fireplace opening is too large, it can draw in more combustion air than your flue can vent. Therefore, pushing smoke back into your living room. 

Ideally, your fireplace opening shouldn’t be more than ten times the cross-sectional area of the flue.

For example, let’s say that your flue opening is 10 inches by 10 inches, equaling 100 square inches. 

Then the fireplace opening should not exceed 10 times this, or 1000 square inches. 

The easiest way to fix this is to install a non-combustible shield at the top of the fireplace opening to lower the effective opening height. 

Even something as small as 3-4 inches will have a huge difference. 

Or you can consider installing glass doors or having a chimney company come and reconfigure your fireplace opening.

The Firebox is too Shallow

If your firebox is too shallow, the smoke can easily roll out near the top of the fireplace, rather than entering the smoke chamber like normal.

The best thing to do in this situation is to install a hood at the top of the fireplace opening. This will help capture the smoke and direct it up the flue rather than into the room.

The Lintel is too High

The lintel is the steel bar supporting the top of the fireplace opening. If it’s too high, it may allow smoke to roll out of the fireplace opening instead of going up the flue. 

The lintel should be at least six inches below the damper frame. 

If not, you may be able to install a shield, as I mentioned above. But you may need to hire a chimney company to raise the lintel for you. 

Fireplace Throat Isn’t Contructed Properly

The fireplace throat is the opening into the smoke chamber.

If it’s not constructed properly, severe smoking problems may result. The throat could be located too far forward. Or it could be too small for the fireplace.

Throat problems usually require a chimney company to rebuild the firebox and throat area. The opening of the throat should be at least one-tenth of the fireplace opening. But a larger throat is common.

Smoke Chamber Isn’t Constructed Properly

The smoke chamber is used to help funnel smoke from the fireplace opening into the flue. 

Improper design is common. And it can lead to plenty of problems. It can be too deep, too tall, or even too wide. It really needs to be just right. 

The National Fire Protection Association recommends that smoke chambers should not be taller than the fireplace opening width. And it shouldn’t be deeper than the fireplace opening. 

Additionally, NFPA states that the smoke chamber walls should not incline more than 45 degrees from their vertical orientation. 

The walls should be smooth to help reduce turbulence. So most building codes require that smoke chamber walls be parged, which means there will be a coating of mortar applied to the bricks to give the smoke chamber a smooth surface.

The flue should start at the top center of the smoke chamber and shouldn’t have any radical offsets or bends. 

We see a lot of problems with corner fireplaces because the smoke chambers tend to be large and irregular. 

Unfortunately, smoke chamber problems are difficult to correct and will require you to hire a chimney expert. 

Chimney Flue is too Short

Short chimneys are pretty common too. They can often lead to smoking problems because they aren’t long enough to provide an adequate draft to pull the smoke out of the chimney.

Your chimney should extend ten feet beyond the fireplace opening.

The best thing to do is to simply raise the chimney.

Improper Termination Height

The chimney should be at least three feet above the point that it passes through the roof. This is the termination height.

This height will allow the sparks to cool before landing on the roof. Otherwise, you risk creating a fire.

In addition to being three feet higher than the spot it came out of, it should also terminate at least two feet higher than anything within 10 feet of the chimney.

This will keep your chimney drafting properly. Otherwise, you’ll have smoke getting pushed back into your home.

These guidelines are just minimums. So even if you meet these, you might still need to raise your chimney to prevent smoking problems.

Home is Too Airtight

Modern homes are often so tight that air can’t move through the home like normal. Smoke can’t rise up through the chimney any faster than air can be drawn into the home to replace it. 

Older homes that weren’t built as efficiently had little pocket holes that allowed air to flow easily through the home. 

Now, the homes are more efficient, but that’s causing a lot of issues for chimneys since they aren’t allowing enough makeup air. 

If you suspect that your home is too airtight, you can try to open a window near the fireplace next time you burn a fire. 

If this cures your problem, then you can consider installing an outdoor air supply so you don’t have to leave a window open to use your fireplace.

Obstructions and Blockages

If your chimney is blocked by creosote, leaves, twigs, animals, or anything else, you’ll have a hard time getting smoke to pass through. 

Creosote is the scariest of all of these since it’s highly flammable and is a natural byproduct of burning. 

Most blockages are easy to fix. Just remove the blockage.

But you could also see a big problem with older chimneys when the inside bricks collapse inside the chimney. 

The easiest blockage to clear is when you forget to open the damper! 

Make sure your damper is open. It can be easy to forget, especially if you don’t use the chimney on a regular basis.

Competing Vents

Anything that will remove air from your home can cause smoking problems in the fireplace. 

A competing vent could be your kitchen or bathroom exhaust. Or it could be your dryer vent or a central vacuum system. 

By drawing air from your house, these devices can cause a flow reversal. 

To prevent this, just make sure all vents are off during  your next fire. If this fixed the problem, you can just add an outside air supply to the house for your fireplace to draw outside air as needed.

Temperature

Your fireplace will work best when it is very cold outside, but your fireplace may smoke when the outdoor temperature approaches the indoor temperature.

If your fireplace smokes when it’s warmer outside, just don’t use your fireplace on moderate temperature days.

Wood Supply

Green or wet wood will cause smoking problems. 

The moisture content needs to be 15-25%. More than that and you have green wood. 

You need to make sure that you are using dry, seasoned wood. It takes about two years to properly season firewood. 

Wind Induced Downdrafts

Wind-induced downdrafts are exactly as they sound. 

They are downdrafts that occur when the wind is blowing in a certain direction. A downdraft is when the wind is drafted down the chimney, instead of the other way around.

Two distinct types of wind-related downdrafts occur when either high pressure or turbulence surrounds the top of the chimney. 

High pressure around your chimney can occur when the chimney is located upwind of an obstruction taller than the chimney. 

As the wind flows towards that taller obstruction, it tends to back up causing a higher pressure. If the pressure is higher than that in the chimney you’ll experience smoke getting pushed back down your chimney.

If the chimney is located downwind, turbulence will be created as the wind flows over and around the obstruction. 

If the chimney top is in the region of turbulence, wind can be forced down the chimney. This usually results in a short burst or gust of smoke pushed into your home. 

A chimney cap usually solves these problems. They’re not just for keeping the rain out!

Fire Starting Practices

Smoking problems can be caused by the way you build your fire. And how you maintain it. 

Building a fire in your fireplace requires the use of tinder, kindling, and firewood. 

The key to building an efficient fire is to think small. Starting your fire will require you to use tinder and kindling. Tinder should easily ignite with a match and begin to burn. 

This will burn the kindling followed in turn by the larger logs. 

Newspapers are good tinder, but kindling can be small dry sticks and branches.

Flow Reversals

Flow reversals occur when the pressure surrounding the fireplace opening is actually lower than the pressure inside the chimney.

This can cause smoking problems pretty easily and can be caused by several things.

Leaks in the upper portions of your home can allow warm air to rise and escape faster than it is replaced with cooler air in the bottom portions of your home.

This will lower the pressure around the fireplace, which can cause smoke flow in the chimney to come out into the room.

This can also happen if someone upstairs opens a window to let in fresh air while you have a fire going downstairs.

Another type of flow reversal can be created when two chimneys are close together. Make up air for the chimney in use can be drawn down the unused chimney, pulling smoke from the flue in use.

Luckily that one is an easy fix. Just close the damper on the unused chimney.

Damper Isn’t Open

If your damper isn’t open, you can have smoke getting pushed back into your chimney. 

That is if the fire even starts. 

Even if you pulled the cord or moved the lever to open your damper, something could be broken that will prevent it from opening all the way.

And that could make it hard for adequate oxygen to get to the fire you’re trying to start.

Wood is too Wet

If you are trying to light a fire with wet wood, you’re going to have a hard time. You may get a lot of smoke, but you won’t be able to get enough of a fire to light.

If there’s no fire, there won’t be enough heat to allow the chimney to draft the fumes up through the fireplace.

And that won’t allow enough oxygen to circulate through the fire.

Gas Supply is Cut Off

This one seems obvious, but it’s more common that you might think.

If there is no gas, there is no fire if you have a gas fireplace.

There is usually a wall switch or a valve near the fireplace that transfers the gas from the mainline or source to the fireplace. Maybe that switch is turned off.

Or it could be that the gas in the tank is empty and you need to have it filled up.

Pilot Light is Out

The pilot light for a gas fireplace can be blown out by a downdraft. All you need to do here is turn the pilot light back on.

Sometimes you could have a broken pilot light and in that case, you should call a chimney company out to fix it.

Gas Valve is Blocked

Even the smallest amount of dust can block the gas valve. The thermo coupling produces an electric spark from the pilot light which opens the gas valve.

Clean the gas valve, because that small amount of dust could be preventing it from lighting.

Poor Draft

Drafting can cause many problems, even preventing your fire from lighting.

If there isn’t enough draft in the chimney, you’ll have a hard time getting the fire going due to a lack of oxygen.

As I mentioned before, there are several things affecting draft: obstructions, chimney height, or even wind.

Chimney is Filled with Cold Air

When the chimney is filled with cold air, there is a possibility that there is a cold column of air pushing down toward the fire.

Since the fireplace doesn’t have enough of a draft, you’ll have a hard time getting the fire to light. And that will cause smoke to get pushed back into your home.

What we’ve seen people do is light a rolled-up newspaper and hold it like a torch inside the flue. This warms up (sort of preheats) the fireplace and helps provide enough of a draft to get the fire started.

Tight Home

That’s not a weird 2000s complement either. I mean your home could be too tight so that air isn’t able to escape in normal ways.

Air has to escape and it’s probably flowing up your chimney in large quantities, which means that there must be a sufficient air supply to move up and out of the chimney and provide oxygen for your fire.

Sometimes modern homes are way too tight to the extent that fireplaces become sluggish, smoky, and won’t burn fires.

Barbeque or Smokey Smell

One of the most common “smells” we hear about during summer is that their fireplace smells like a dirty barbeque grill. 

Even with the fireplace doors and damper closed, you may smell smoke taking over your living room. 

Smokey smelling chimneys and fireplaces are caused by the chimney being full of soot and creosote. 

A simple chimney sweep will clear away all the creosote, soot, and ash that are causing the smells.

Mold & Mildew

If you smell mold and/or mildew, it’s pretty clear that you’re facing a chimney leak. 

Not only is your chimney leaking, but it’s been leaking long enough for bacteria and spore growth to develop. 

By the time you smell and notice moldy/mildewy smells, you likely have hidden damage in your chimney system.

If you smell mold or mildew, you should give us a call to take a look inside and out of your chimney. With an inspection, we’ll be able to see what’s causing your chimney to smell. 

Foul or Decomposition

This one’s the worst smell. 

You can’t mistake the smell of some animal decomposing. 

You might think that something got into your chimney and died. Maybe a squirrel or a bat. 

You’re not wrong, but it doesn’t have to be an animal. It could actually be any organic material that’s decomposing in your chimney. 

That’s leaves, wood, twigs, feathers, animal droppings, etc. 

A chimney sweep can come in and clean the inside of your chimney. We can also assess the top of your chimney to see how these things got in. 

It could be that you need a cap to cover the top of your flue.  

Black Stains

If your chimney has black stains, it’s most likely the result of excess creosote and soot build up inside your flue.

When your chimney isn’t cleaned regularly, creosote continuously builds up, creating a thicker and thicker layer on the walls of your chimney flue.

The build-up of creosote will keep your chimney from drafting properly. Basically that means you could have smoke filling your chimney instead of exhausting up and out of your chimney.

Eventually, your dirty flue will show itself by creating soot stains on the exterior.

Most soot stains can just be the result of age or lack of regular cleaning and maintenance. But it can also indicate a hidden chimney problem.

When the creosote build-up is bad enough to cause exterior staining, you may need to get your chimney relined.

NOTE: Gas fireplaces should never have exterior staining from soot. If you have soot stains and your fireplace is gas, this can indicate a carbon monoxide leak or another dangerous malfunction.

Dark Green or Bluish Stains

Dark green or bluish stains are pretty hard to differentiate between black stains caused by soot unless you’re up close and personal with your chimney.

Dark green or bluish stains are caused by algae growth. It’s often seen in areas where the water has been allowed to pool or consistently flows.

For example, a commonplace for this type of stain is around the chimney crown, when the chimney crown doesn’t have an appropriate overhang.

In a perfect world, all components are performing their functions to keep moisture out.

But the biggest design flaw in exterior masonry chimneys is the fact that bricks are porous. That means they absorb water.

In the wintertime, this could result in freeze/thaw cycles which can cause your chimney bricks to crack and ultimately will lead to your chimney leaking anytime it rains.

It’s important to have these troubled areas corrected so that it doesn’t cause any additional problems later on down the road.

Red or Brown Stains

Red, brown, or “rust-colored” stains are most often seen on the sides of metal or prefabricated chimneys. It’s rust-colored because it’s….you guessed it….rust!

When the rust stains begin to appear on the sides of your chimney, that’s a sign that your chase cover is probably leaking and you should have a chimney company take a look.

Rusted chase covers can allow for pinholes on top. Those pinholes in the rusty chase cover will allow water to get inside your chimney.

You should have rusted chase covers replaced as soon as possible to prevent water damage to the fireplace and chimney.

Luckily, these days, you can get stainless steel chase covers that will not rust.

If you don’t have a metal or prefabricated chimney, but you’re still seeing rust-colored stains, it’s likely that you still have some component rusting.

That could be your cap or the flashing around your chimney.

Rust stains on any chimney are indicative of a potential leak and should be taken care of as soon as possible.

White Stains

In the chimney industry, we call this efflorescence.

That means that water-soluble salts within your chimney’s masonry have mixed with water. Those salts have traveled to the exterior part of the chimney, leaving deposits that will cause chimney discoloration.
The powdery white staining is easily washed off and does no harm itself.

But when efflorescence appears on the outside of your chimney, it’s pretty clear that you have some type of water damage to your masonry.

The problem with water in the masonry, as I’ve already mentioned, is that during freeze/thaw cycles, your brick will expand and contract.

Over time, this will cause your chimney to deteriorate.

You might notice a pile of debris beneath your chimney. This is evidence of the brick face popping or breaking off from deterioration.

When you see efflorescence the best thing to do is replace the affected bricks. Otherwise, I’m afraid, your chimney will eventually weaken to the point of leaning and potentially collapsing.

Questions to Ask

When you’re hiring a chimney company, you should always ask the following questions before allowing them to come into your home:

1. Can the company provide references? 
2. Does the company carry a valid business liability insurance policy? 
3. Does the company ensure that a certified chimney technician will be on the job? 

If they guarantee all three of those, then you are in a good spot. The technicians don’t necessarily need to be certified by the CSIA, but I do recommend putting in a bit more due diligence before accepting a certification that’s not by the CSIA. 

This is because certifications are a tricky thing, especially in an unlicensed industry like ours. Any company can craft a list of job-related questions and sell them as an exam and certify those who pass.

Certifications

I recommend you take a few extra minutes in your research before making your hiring decision to learn more about the certification the company has. Here are a few tips to make sure the certification is reputable: 

• Is the word “certified” just part of the business name or is it an earned designation? 
• Is the certifying body a for-profit business or non-profit? 
• Does the certification need to be maintained and renewed through continuing education as the industry evolves, or is it well enough to be certified through a one-time exam? 
• Is the certifying body well-established or are they relatively new to the scene? New doesn’t mean “bad” but you should make sure the requirements for certification are more or at least equally stringent as those of more established certifications
• Is the mission statement of the certifying body focused on educating and protecting homeowners or is it more focused on making it easier to earn a certification? 
• Does holding the certification require following a code of ethics? 

If you can answer all of these questions, then I think it will be safe to allow the company in your home to work on your chimney. 

Please note that If you are hiring a chimney company to install a cap for you, most of the time, they will need to buy the cap themselves. This is primarily for liability and insurance purposes. 

Besides, it’s probably cheaper for them to buy a cap at the dealer discount than for you to buy one at retail cost.

It doesn’t matter if you are in Roanoke, Lynchburg, Blacksburg, or some other city anywhere in the USA — if you have any questions about the safety of hiring a chimney company, please don’t hesitate to email me at mitchell@patriotchimney.net or call me at 540-225-2626. I’m happy to help!