We get at least one of these questions almost every week so maybe I can help by answering them here. Some of them have “do it yourself” answers, but not all of them. In some cases the answer is to get a professional in to look. Here’s what people want to know.
1) How to tell if your chimney is safe to use.
That’s a big one; unfortunately it is such a broad question that it can’t be answered without actually looking at the chimney. Even then it is highly unlikely that you can get anyone to use the word “safe.” We live in a litigious society and it’s just not smart to call something safe. You’re more likely to see wording such as “No apparent problem.” Don’t try to make a sweep or inspector use the word ‘safe’ rather ask him if he’d be comfortable if it were his mother’s chimney.
To the original question however, the best way is to get as much info about this as you can by calling a certified sweep to look at it. F.I.R.E. Certified inspectors are perhaps the most careful inspectors of all. Listen carefully to the opinions offered and make a judgement of your own.
2) How to tell if your chimney needs sweeping or cleaning.
How to tell if a fireplace needs to be cleaned. In the case of a fireplace you can look with a bright light. Look from top and bottom. In many cases the top will be cleaner than the bottom (for varied reasons I won’t go into here.) If you see ¼ of an inch or more soot, have it swept.
How to tell if a woodstove or stove insert needs to be swept. If you use a woodstove or insert, just assume it needs sweeping if you’re using it. But you can do the same thing, check from top and bottom, pulling out the stovepipe as well. If you see a shiny deposit, don’t try to sweep it. Call a professional and tell him you have third degree creosote. He’ll need to do more than brush it. We have an article that explains the different types of creosote here.
How to tell if a gas or oil flue needs to be cleaned. If it’s a gas or oil flue you have to pull the pipe out at the bottom. There is often not much to see, and if the burner has been operating properly there may not be much to clean. So said, you have to make sure the passage is open. Not a bad idea to pass a brush through for that purpose alone.
3) How to tell if your chimney is on fire.
If you ask yourself “Do I have a chimney fire” you probably have seen or heard something. Usually when we get this call, they know it’s on fire. There may be flames coming out of the top of the chimney, or at least mountainous billows of black smoke. There may be a sound like a freight train is driving through your living room, though you don’t always have the sound effects, and might never know except a neighbor knocks on the door and tells you about the flames or smoke. It’s a real event so you’ll usually know!
Signs of a chimney fire
- There are flames coming out of the top of the chimney
- There are mountainous billows of black smoke coming out of the chimney
- The chimney may sound like a freight train
4) How to tell if your chimney flue is open.
What people usually mean when they ask this question is how to tell if the chimney damper is open. It’s a common thing to refer to the damper as the flue. (The flue is actually the passage the smoke goes through; it’s just the empty space in the vent or chimney. The damper is the thing that opens and closes to let the smoke go up the chimney.)
So how can you tell if it’s open?It’s simple really, but you usually have to get on your knees and look up from underneath. If you see some sort of flapper or plate open or shut, that’s it. There’s usually a handle to operate the damper and you might want to mark the open and shut positions somehow so you don’t have to go through all that every time.
5) How to tell if the chimney is blocked.
Many times a visual inspection will tell you. Of course, in the case of wood or oil, if the flue is blocked smoke or smell of oil fumes will fill the house, which is a probable indicator. With gas however… the fumes are odorless and colorless so you may not know until the household is sick or dead of asphyxiation. Gas flues, while posing a very small fire danger, have the worst numbers for trouble.
Gas flues should never need to be cleaned if the burner is working properly, but should be inspected each year. I advocate running a brush through the flue to get spider webs or bits of nests that might be in there, regardless of whether you believe you can see all the way to the bottom. And if there’s a bend in the chimney, you just can’t tell by looking.
One other thing: you often can see if a flame is drawn toward the flue from the bottom, and this can be useful, but don’t rely on it if you can’t also see from top to bottom that everything is completely clear. A partially blocked chimney will let the flame be pulled toward it, but it may not vent all the gasses; you could still get CO poisoning.
6) How to tell if the chimney has a liner.
Unless you live in an old farmhouse, it is extremely unlikely that you DON’T have some kind of liner. For most of our lifetimes, new buildings have had fireclay liners installed when built.
This question most often means “how can I tell if I have a stainless steel liner” which is very easy to ascertain. Don’t try to figure it out from the bottom of your flue even though often you will be able to find out there. The sure way is to go to the roof and look down. If you see a round steel tube for the liner- you’ve got one. If you have a square or rectangular clay tile “tube” then you have a tile liner, not a stainless steel liner.
7) How to tell if the chimney is leaking.
That usually means is water getting from inside the chimney to a wall or ceiling somehow. How the water gets in there in the first place is a subject we covered in depth in our chimney leak article but to answer this question, you probably won’t really know unless you have some visual clue such as water puddling or perhaps staining on the wall or ceiling. You should look at the chimney crown and the mortar joints above the roof. There may be a cracks there and even though water isn’t infiltrating in some visible way, your masonry will break up faster and faster because of freezing and thawing.
8) Are chimney caps necessary?
We recently had 16 continuous days of rain, one day of sun and then another four days of rain. We got a lot of leaking chimney calls during that time. People complained that the chimney leaks water in the basement or around the roof. Most of these folks did not have chimney covers, which is the first line of defense from rain in the chimney. Again, check the link above to learn more about leaky chimneys. If you don’t know if you have a chimney cover, the way to check that is just to look up at the top of the chimney and see if there’s “a bird cage with a lid” up there. If not, don’t wait for the rain; call a sweep to put up a chimney cover while the sun is shining!