When the temperature drops and you’re ready to light your stove or open fire for the first time in months, it’s worth doing a few checks before reaching for the matches.

A chimney that worked perfectly well last winter may have been unused throughout spring and summer. Birds may have attempted to nest, the stove may need some attention, or the chimney may simply be full of cold air that needs warming before it will draw properly.

In fact, one of the most common calls we receive at the beginning of the heating season is from customers whose chimney was swept earlier in the year but who find that smoke comes back into the room when they light their first fire.

That doesn’t necessarily mean the chimney is blocked.

Here are the checks we’d recommend before lighting your first fire of the season — including a simple way to test whether your chimney is drawing before you fill the room with smoke.

1. When Was Your Chimney Last Swept?

Sweeping frequency depends on the fuel being burned and how the chimney is used. HETAS encourages sweeping at least twice a year when burning wood or bituminous house coal and at least once a year when burning smokeless fuel. Cambridgeshire Fire and Rescue Service advises that wood-burning chimneys may need sweeping up to four times a year.

If you had your chimney swept in spring and haven’t used it since, it doesn’t automatically need sweeping again simply because winter has arrived.

However, if it hasn’t been swept within the appropriate interval, or you’re unsure of its condition, arrange a sweep before returning it to regular use.

It’s also worth remembering that sweeping isn’t only about removing soot. It gives your chimney sweep an opportunity to identify things such as debris, nesting material and other obvious issues encountered during the sweep.

How often should you have your chimney swept?

2. Check for Signs That Birds May Have Nested

An unused chimney can be an attractive nesting place for birds during spring and summer.

The clearest warning sign we see is twigs coming down the chimney.

If twigs or nesting material have fallen into your fireplace, don’t assume the rest of the chimney is clear. Birds may have started building a nest further up the flue.

In that situation, we’d recommend having the chimney checked and swept before lighting a fire.

There may be other signs too, including bird activity or noises from the chimney, but twigs appearing in the fireplace are particularly difficult to ignore.

Remember that active bird nests are protected while they are in use. We don’t remove bird nests between 1 April and 31 August. From September, once the nesting season has ended, we can remove nesting material and sweep the chimney where appropriate.

Read our guide to bird nests in chimneys.

3. Give the Stove or Fireplace a Quick Check

Before lighting anything, have a look at the appliance and fireplace.

You’re not trying to carry out a professional inspection. You’re simply looking for anything obviously different from when you last used it.

For a stove, that might include damaged glass, broken fire bricks, a door that isn’t closing properly, damaged rope seals or air controls that have become difficult to operate.

If you use a stove, our Wood-Burning & Multi-Fuel Stove Maintenance Guide explains the routine checks you can carry out yourself and when professional servicing may be worthwhile.

If you notice significant damage or something you’re concerned about, get it looked at rather than assuming it will be fine once the stove gets hot.

4. Test the Chimney Draw Before Lighting the Fire

This is one of the simplest checks you can make — and one we particularly recommend when a chimney hasn’t been used for several months.

Before building your fire, light a joss stick or a small piece of paper and hold it safely near the fireplace opening or appropriate flue entry point.

Watch what the smoke does.

If the smoke is being pulled clearly upwards into the chimney, that’s a good indication that you have an upward draw.

If the smoke barely moves, hangs around the opening or comes back towards the room, don’t light a full fire yet.

There are several possible reasons for poor draw, including a blockage — but at the beginning of the heating season there’s another very common explanation.

5. Your Chimney May Simply Be Cold

This catches people out surprisingly often.

A typical example is somebody who had their chimney swept in April or May. It hasn’t been used since, so when the first cold evening arrives several months later they light the fire expecting everything to work perfectly.

Instead, smoke comes straight back into the room.

Understandably, the first thought is: “My chimney must be blocked.”

It might be — but often it isn’t.

A chimney relies on draught to carry the products of combustion upwards. Temperature differences are an important part of creating that draught.

After several months without a fire, you can effectively have a column of cold air sitting inside the chimney. When you try to light a fire underneath it, the initial warm air and smoke may struggle to rise against that cold air.

The result can be smoke spilling back into the room even though the chimney itself was swept and is clear.

6. Try Warming the Chimney First

Before assuming you have a blockage, try warming the air inside the chimney.

One very simple method is a hairdryer.

Direct warm air safely up into the chimney for a couple of minutes. The aim isn’t to heat the entire chimney; you’re simply trying to start warming the cold air inside it and encourage an upward movement of air.

Then repeat your joss-stick or paper test.

If the smoke that previously sat around the fireplace is now being pulled upwards into the chimney, you’ve established a much better draw before lighting the fire.

This simple trick solves the problem surprisingly often for customers at the beginning of the heating season.

However, if warming the chimney makes no difference and the smoke still isn’t being drawn upwards, don’t just build a bigger fire in the hope that it will sort itself out.

There may be another reason for the poor draw that needs investigating.

7. Start With a Small Fire

Once you’ve checked the chimney draw and the smoke from your joss stick or paper is travelling upwards, start with a small fire.

Use dry kindling and a small amount of appropriate fuel rather than immediately loading the fireplace or stove for a large fire.

As the small fire establishes, it will continue warming the chimney and strengthening the draw.

You can then gradually build the fire as everything warms up.

If you’re burning wood, use dry wood with a moisture content of 20% or less. Wet wood makes it harder to establish a good, clean-burning fire and contributes to unnecessary smoke and deposits within the chimney.

8. Keep an Eye on That First Fire

Your first fire after several months of non-use is a useful opportunity to pay attention to how everything is behaving.

Smoke should be travelling up the chimney rather than spilling persistently into the room.

With a stove, the fire should become controllable as it establishes. You shouldn’t need to compensate for poor performance by continually opening doors or improvising with the controls.

If something doesn’t seem right, don’t assume that because the fire worked last winter it must still be fine.

Stop and investigate.

What If Smoke Still Comes Back Into the Room?

If smoke comes back into the room when you first try to light the fire, don’t immediately panic — particularly if the chimney has been unused for several months.

1. Stop adding fuel.
2. Allow the fire to go out safely if you’ve already lit it.
3. Once safe to do so, try warming the chimney with a hairdryer for a couple of minutes.
4. Repeat the joss-stick or paper smoke test.
5. If you’ve established an upward draw, try again with a small fire.

If the chimney still isn’t drawing properly, don’t continue lighting fires to try to force it.

Poor draw can have several causes. There could be a blockage such as nesting material or debris, or there may be another issue affecting the chimney’s performance.

That’s the point at which it’s sensible to get professional advice.

Cold Chimney or Blocked Chimney?

Unfortunately, you can’t always diagnose the cause of poor draw simply by looking at the fireplace.

A useful starting point is what you already know.

If the chimney was professionally swept in spring, hasn’t been used since and there have been no signs of nesting, a cold chimney is a reasonable possibility.

If you’ve seen twigs or nesting material falling down the chimney, that’s a very different situation. Don’t light the fire until the chimney has been properly cleared and swept.

Likewise, if warming the chimney doesn’t establish an upward draw, don’t assume you simply need an even bigger fire.

The important thing is not to use fire as your test for whether a chimney is clear.

A joss stick or small piece of paper gives you a much safer opportunity to see what the air is doing first.

FAQs

Why does smoke come back into the room when I first light my fire?

There are several possible causes, including a blockage or a problem with chimney draught. At the beginning of the heating season, however, a chimney that hasn’t been used for several months can simply be very cold.

The initial smoke can struggle to rise through the cold air sitting inside the chimney and spill back into the room.

Try warming the chimney for a couple of minutes before testing the draw again. If the problem persists, stop using the fire and investigate further.

How can I test whether my chimney is drawing?

Before lighting the fire, use a lit joss stick or small piece of paper and watch where the smoke travels.

You want to see it being pulled upwards into the chimney. If it remains stagnant or moves back towards the room, don’t light a full fire until you’ve established why.

Can I use a hairdryer to warm a cold chimney?

Yes. It’s a simple technique we regularly recommend to customers who experience poor initial draw after their chimney has been unused for several months.

Direct warm air safely up the chimney for a couple of minutes and then repeat the smoke test before lighting the fire.

My chimney was swept in spring. Could it already be blocked?

Potentially, which is why you shouldn’t automatically assume poor draw is caused by cold air.

Birds can attempt to nest in chimneys during spring and summer. Twigs or nesting material falling into the fireplace are a particularly strong indication that you should have the chimney checked and swept before using it.

If there are no signs of a blockage and the chimney was swept before its period of non-use, a cold chimney may be the explanation.

Should I light a big fire to warm a cold chimney quickly?

No. Check the draw first.

If necessary, warm the chimney with a hairdryer and repeat the smoke test. Once you’ve established an upward draw, start with a small fire and build it gradually as the chimney warms.

How often should my chimney be swept?

Sweeping frequency depends on the fuel being burned and how the chimney is used. HETAS encourages sweeping at least twice a year when burning wood or bituminous house coal and at least once a year when burning smokeless fuel. Cambridgeshire Fire and Rescue Service advises that wood-burning chimneys may need sweeping up to four times a year.

See our How Often Should You Sweep Your Chimney? guide for the full guidance.