Why Does Campfire Smoke Follow You?

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Why Does Campfire Smoke Follow You
Campfire smoke follows you because your body acts as an air dam. It blocks air moving toward the fire, creating a vacuum so smoke moves toward you. If you move, the smoke moves, too.

Does it seem like campfire smoke follows you? You sit down and enjoy the fire and soon there’s smoke in your face. So, you move to the other side of the fire and before long, the smoke is right there with you. It’s not your imagination. Smoke really does follow you. Here’s the science of how it works and how you can prevent it from happening.

How a Campfire Works

Before getting into why campfire smoke follows you, it helps if you understand the basics of how fire works.

Fire needs three things: heat, fuel, and oxygen. The initial heat source is a match or something similar. Once the kindling catches, a fire supplies its own heat that sustains combustion. Wood is the fuel for a campfire. It contains impurities and does not burn perfectly. This incomplete combustion releases carbon monoxide and soot, in addition to other products, producing smoke. Finally, fire needs oxygen, which it gets from fresh air.

As a fire burns, heat imparts kinetic energy to molecules. Increasing kinetic energy results in more collisions between molecules. They move further apart and the density of hot air decreases. Because it’s less dense than the cooler air around it, hot air rises, carrying the smoke with it. The pressure difference allows dense, cool air to flow in toward the fire, supplying it with fresh oxygen.

Colored fire campfire

How to Color Your Campfire

Coloring your campfire flames won’t affect whether smoke follows you, but it adds zing to your fire.

Why Smoke Follows You Around a Fire

When you sit beside a campfire, you interfere with the fire’s air flow. Your body blocks fresh air from moving toward the fire. This causes a pressure difference between your body and the fire. Think of it as a partial vacuum. Now, hot air still rises, but it rises at an angle as air moves into the low pressure region between you and the fire. Now you’ve got smoke in your face and the campfire just became a lot less fun. The only plus side is mosquitoes have a harder time finding you with all that carbon dioxide masking your “scent”.

So, you move to the other side of the fire. Everything is fine for a while, but after a few minutes the smoke works its way back to you. One option is constantly changing your position around the fire. Fortunately, there are better solutions.

Dakota Fire Hole
A Dakota fire hole is a type of campfire that minimizes smoke. The fire is contained within a pit, which has an air trench.

How to Keep Smoke From Following You

There are a couple of ways of keeping campfire smoke from following you.

  • If you’re enjoying the fire with friends, space yourselves around the fire equally. This makes the air pressure more or less the same in front of each of you, so the smoke goes up instead of toward one of you.
  • On the other hand, if you are fireside with people you don’t like, just sit on the opposite side of the largest cluster of people or largest person. The smoke follows them, not you!
  • If you’re on your own, construct a smokeless fire. Basically, you pre-determine the air flow. A good model is the Dakota fire hole, which has the fire contained within a pit that gets its air from the side. Ideally, the pit contains the smoke. But, if some escapes it moves in a definite direction so you can avoid it. Another model places the fire within a horseshoe of stones, with a large flat rock opposite the open area.

References

  • Lackner, Maximilian; Winter, Franz; Agarwal, Avinash K., eds. (2010). Handbook of Combustion. Wiley-VCH. ISBN 978-3-527-32449-1.
  • McGough, Will (January 3, 2018). “The 5 Types of Campfire and When to Use Them”. Backpacker.
  • “Survival Manual Winter 2002“. US Marine Corps Mountain Warfare Training Center.