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How does a lighter work?

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Quick answer

Pressing the lever opens a valve, releasing butane that was stored as a liquid under pressure. The fuel escapes as vapour, mixes with air, and is lit by a spark from flint or a piezoelectric crystal. Heat from the flame boils more liquid fuel, sustaining the flame until you release the lever and the valve closes.

A lighter works by releasing a small jet of fuel gas that mixes with air and is ignited by a spark, producing a steady flame. The heat of that flame then keeps vaporising more liquid fuel, so the flame sustains itself until the valve is closed.

Step by step

  1. Liquid butane sits under its own vapour pressure inside the sealed fuel chamber.
  2. Pressing the lever lifts a valve, letting vapour escape through a narrow nozzle.
  3. The jet of gas expands, slows, and mixes with oxygen in the surrounding air.
  4. A spark from flint-and-steel or a piezoelectric crystal ignites the fuel-air mixture.
  5. Heat from the flame boils more liquid butane into vapour, feeding the flame continuously.
  6. Releasing the lever closes the valve, cutting off fuel and extinguishing the flame.

Key things to understand

  1. Liquid fuel such as butane is stored under pressure inside the sealed body of the lighter.
  2. Pressing the lever opens a valve, letting pressurised fuel escape as a vapour through a narrow nozzle.
  3. The escaping gas expands and mixes with oxygen in the surrounding air to form a flammable mixture.
  4. A spark from a flint struck by a steel wheel, or from a piezoelectric crystal, ignites that mixture.
  5. The flame's heat boils more liquid fuel into vapour, so the lighter keeps burning until the valve shuts.

Labelled diagram

  1. Fuel chamber

    Liquid butane stored under pressure, with vapour filling the space above it.

  2. Valve and lever

    Pressing the lever opens the valve, releasing fuel vapour through a narrow opening.

  3. Nozzle

    The jet expands and slows, mixing with oxygen from the surrounding air.

  4. Ignition

    A spark from flint or a piezoelectric crystal lights the fuel-air mixture.

  5. Flame

    Heat boils more liquid fuel, sustaining the flame until the valve closes.

How a butane lighter makes a flame

Real-world examples

  • A disposable pocket lighter uses a flint wheel and a plastic body holding liquid butane under pressure.
  • A refillable metal lighter, such as a Zippo-style design, uses a wick and cotton packing soaked in lighter fluid.
  • A gas barbecue igniter uses a piezoelectric spark to light a burner fed by propane rather than butane.
  • A kitchen blowtorch lighter produces a hotter, blue flame by mixing butane with extra air before burning.

Common mistake

✗ Myth: Many people think the lighter burns liquid fuel directly.

✓ Fact: The flame actually burns fuel vapour mixed with air, not the liquid itself. Liquid butane must first evaporate, which is why a lighter fails in extreme cold when vaporisation slows.

People also ask

What is lighter fluid made of?
Most lighter fluid is a petroleum distillate such as naphtha, a mixture of light hydrocarbons that evaporates easily at room temperature. Disposable gas lighters instead use butane, which is stored as a liquid under pressure and boils into vapour as the valve opens.
Why does a lighter spark but not light?
A spark with no flame usually means fuel is not reaching the ignition point, often because the valve is clogged, the fuel is nearly empty, or the nozzle is blocked. Cold temperatures can also slow vaporisation so much that the mixture stays too lean to ignite.
Can you take a lighter on a plane?
Aviation rules generally allow one common lighter in your pocket or on your person, but not in checked baggage, and torch-style lighters are usually banned. Rules vary by country and change over time, so check your airline's current guidance before flying.
Why does a lighter still work if you shake it or hold it upside down?
Butane is stored as a liquid with vapour above it, and a wick or tube draws from the liquid region, so orientation usually does not stop fuel reaching the valve. Holding it upside down can briefly release liquid instead of vapour, which may flare before settling into a normal flame.
What is the difference between a flint lighter and a piezoelectric lighter?
A flint lighter grinds a small piece of ferrocerium alloy against a hardened steel wheel, throwing off sparks that ignite the gas. A piezoelectric lighter instead compresses a crystal, which generates a high-voltage spark across a gap near the nozzle, with no flint to wear out.
Why does the flame sometimes go out right after lighting?
The gas jet can be too weak or too strong to stay within its flammable range in air, so the mixture either is too lean or too rich to keep burning. Wind, a clogged nozzle, or low fuel pressure can also blow the flame away from the ignition point before it stabilises.
Is the flame of a lighter hot enough to melt metal?
A typical butane lighter flame reaches roughly 1,000 to 1,300 degrees Celsius, hot enough to soften some thin metals and solder but not to melt bulk steel. It is far cooler than an oxy-acetylene torch, which can exceed 3,000 degrees Celsius.

Part of the guide: Everyday Science: Light, Heat & Matter →