Chimney, Fireplace and Stove Problems: What to Do First
The single most useful thing about chimney problems is knowing which situations are an emergency call and which are a service call, because getting that order wrong costs time when time matters. Four things belong to the emergency services before they belong to anyone else: a chimney fire, a carbon monoxide alarm, any smell of gas, and a room filling with smoke that is not clearing. In all four the sequence is the same: everyone out of the building, then call 911 or your gas utility from outside. Do not restart the appliance to see whether it repeats, and do not wait for a technician. Everything else on this page is a diagnosis problem instead of an emergency, and most of it comes down to four underlying causes: deposit, blockage, water, or an appliance component that has worn out.
Which call comes first, by symptom
The single most consequential table on this site. Getting the order wrong costs time when time matters.
| Symptom | First call | Use the appliance? |
|---|---|---|
| Chimney fire happening now | 911, from outside the building | No |
| Carbon monoxide alarm sounding | 911 or your gas utility, from outside | No |
| Any smell of gas | Gas utility or 911, from outside | No |
| Room filling with smoke, not clearing | 911, from outside | No |
| Chimney fire that went out by itself | Chimney service: Level 2 inspection | No, not until inspected |
| Masonry falling from the stack | Chimney service; keep people clear below | No |
| Sudden total loss of draft | Chimney service | No: treat as a blockage |
| Startup puff that clears | Chimney service, routine | Yes, while it is diagnosed |
| Water staining after rain | Chimney service, routine | Yes |
| Glass blackening quickly | Chimney service, routine | Yes |
Work it out from the symptom
The service triage tool takes the symptom closest to what is happening and returns the stop condition that applies, the page explaining that problem, and the service it maps to: in that order, because the stop condition is the part that matters first.
The four that are a 911 call first
A chimney fire. A carbon monoxide alarm sounding. Any smell of gas. A room filling with smoke that does not clear. Get everyone out, then call from outside. Carbon monoxide in particular has no smell, no colour and no taste, so the alarm is detecting something your senses cannot, which is exactly why the response is to leave, not to investigate.
The stage people skip
After the emergency has been handled there is a second step that gets missed, and it is the one behind most serious repeat incidents. A chimney fire can crack flue tiles and open the joints between them with nothing visible from the room. The system needs a Level 2 inspection before anything is burned in it again. The pattern behind most bad outcomes is a first event that was survived and never investigated.
Sudden versus chronic tells you a great deal
A problem that appeared overnight in a system that always worked commonly means a blockage: a nest, a collapsed liner, a blocked cap, snow or ice at the termination. A problem that has always been there is commonly a design or sizing issue: an oversized flue, a cold exterior chimney, a termination too low for the roof, or a fireplace opening out of proportion with its flue. Those are different investigations.
Fourteen problems, grouped by urgency
Call 911 or your gas utility first
Stop using the appliance
Not an emergency: do not leave it either
Chimney leaking
Flashing, crown or cap: the symptom names the source.
Chimney odour
Why a cold fireplace smells in July, and what fixes it.
Creosote buildup
The stages, and where the stop-use line sits.
Cracked crown
The small crack up top causing damage a long way down.
Spalling brick
Why sealing a spalling chimney makes it worse.
Common questions about working out what is wrong
How do I know whether this is an emergency?+
If the room is filling with smoke and not clearing, if an alarm is sounding, if you can smell gas, or if you believe a chimney fire is happening. Those are emergencies. Get out and call 911 from outside. Everything else can be diagnosed.
The alarm stopped on its own. Is it over?+
No. An alarm that stops may mean the level dropped below its threshold instead of that the source has gone. You cannot establish that from inside the building, so the sequence does not change: leave, call, and let someone with an instrument decide.
Can I keep using the appliance while I wait?+
It depends entirely on which problem you have, and the two answers look identical from inside the room. After a chimney fire, a CO alarm or a structural failure, no. After a startup puff that cleared, commonly yes. Ask specifically, not assuming.
Why does the same symptom have several causes?+
Because a chimney is a system and most symptoms are the end of a chain. Smoke in the room can be a cold flue, a closed damper, a blockage, house pressure or a sizing problem. Naming the dominant cause is what a diagnosis is for.
What information helps most when I get in touch?+
The appliance, the fuel, when it was last serviced, and whether the problem is new or has always been there. That last one narrows the possibilities more than anything else you can tell us.
Should I take photographs?+
From the ground and from inside, yes: they help considerably. What you must not do is get onto a roof, or walk up to a stack that is shedding masonry, to improve the shot. No picture is worth that, and the inspection carries the technical evidence regardless.
Is a smell always a problem?+
Commonly it is deposit plus airflow, which is ordinary. The exception matters though: a sharp, acrid or gas-like smell near a fuel-burning appliance is a combustion indication instead of an odour complaint, and it is treated differently.
My problem is not listed here.+
Describe it in your own words when you get in touch. These pages cover what comes up most often, and a chimney can do things that do not fit a category. What you are seeing and when it started is enough to start from.
Do these pages replace an inspection?+
No, and they are not meant to. They help you understand what you are looking at, ask better questions and know when to stop using something. Nothing read on a website can establish that a specific chimney is sound.
How urgent is a leak?+
Not urgent in the way a fire is, and not something to leave for a year either. Water in masonry does incremental damage on every freeze-thaw cycle, and this climate supplies a great many of those each winter.
Why does the site keep saying stop using it?+
Because a combustion appliance does not fail by being annoying. Anything that is not leaving through the flue is arriving in the room instead, and carbon monoxide gives you no warning you can sense. Repeated because it is the part that matters.
Can I diagnose it myself?+
You can get a long way. The self-checks on each page are useful and some of them solve the problem. What you cannot do from the ground is see the inside of a flue, which is where a large share of the real answers are.