My chimney is clear but blows smokes back into the room. Why?

Loading extra kindling onto a fire

I often get asked how can you stop a fire smoking back into the room. It can happen for a variety of reasons, one of which being that your chimney is blocked. That’s why it’s always important to have it swept regularly.

However, if you have had it checked by a professional and other potential causes such as bird’s nests, downdraughts or lack of ventilation into the room have been ruled out, it’s likely that the air pressure outside is literally pulling the smoke back down your chimney and into the room.

Picture the scene; it’s really chilly outside and you want to get your fire going. But if you’re cold, just think how your chimney will feel. It may not have been used for a while. It may not have any insulation. It may be on an outside wall – yes, even things like this can contribute to smoke blowing back into the room even when your flue is clear.

For chimney sweeps, we have the same problem when the air is too warm outside to produce a ‘draw’. That’s why it’s sometimes necessary for us to use a heat gun or blow torch to warm the flue before we conduct a smoke draw test as part of a normal sweep.

In both situations, the trick is to warm the flue before large amounts of smoke are produced. So let me introduce you to the Upside Down Fire or the Top-Down Fire method.

Contrary to popular belief, starting off with small bits of wood and then adding more fuel onto a fire isn’t the greatest way of getting your fire going.

Let me take you through the method first, and then I’ll explain why it works:

Coal being loaded into a fire grate

Step One: Put A Layer of Your Main Fuel On The Bottom (I’ve used coal in this but you can use wood if you prefer)

Firelighters to start a fire

Step Two: Add Some Firelighters


Lighting firelighters

Step Three: Light The Firelighters

Adding kindling to a fire

Step Four: Add Some Kindling

Loading extra kindling onto a fire

Step Five: After About 3 Minutes, Add Some More Kindling

You can vary this slightly by putting kindling on top of the main fuel, then putting the firelighters on top if you wish, but the results are broadly the same.

So what’s happening? It’s simple – the flue is being warmed by the firelighters and kindling. Both produce predominantly flames and warmth, which is therefore warming the chimney and creating a good ‘draw’ or draught.

And because your main fuel has already been loaded onto the fire at the beginning, it will catch light eventually. By that stage the main fuel will have been ‘warmed’ as well (yes, cold fuel creates more smoke) and also, because it’s already in the grate, you’re not having to ‘smother’ the fire with the main fuel.

The net result is a fire which draws better and produces less smoke. This is good news because smoke, as it goes up the flue, can condense and leave deposits inside your chimney/liner. That’s why it’s important, if you are burning wood, that it is good quality, seasoned wood with a moisture content of around 20%. Anything higher and you are simply sending more vapour into the flue, which is bad news and contributes to things like chimney fires and damaged liners.

It’s worth adding that this method works great for both indoor and outdoor fires, so if you’re planning a camp fire or barbecue, it’s worth following these steps.

Haven’t tried the Top-Down method yet? Why not give it a go and let me know how you get on? But remember, never light a fire if you suspect your flue is blocked. Get the professionals in, because smoke inhalation/carbon monoxide can be fatal.

Mr Soot Chimney Sweep offers a professional and friendly chimney sweep service in Wigan, Stockport, Southport, Ormskirk, Chorley, Warrington, South Preston and surrounding areas. Book Mr Soot online or call 0800 0541154.

6 thoughts on “My chimney is clear but blows smokes back into the room. Why?

  1. Thank you and Joanne Thurgur our lovely professional sweep who posted this on Facebook, it’s really really useful. I’ll test it this winter and let you know

  2. I had this problem as my chimney is on an exterior wall. The solution is simple: before you light your fire put your hand under the flue and feel if there is a cold draft coming down the chimney that could blow smoke back into the room, if there is, get your firelighters and kindling ready to go as per the instructions above then take a hairdryer and blow hot air up the chimney. When you turn off the hairdryer and feel that the cold draft is no longer blowing, light the fire.

  3. I have a chimney that puts smoke into my living room. The fire grate is larger than the opening of the chimney.

Leave a Reply