Smoke is likely the first thing to come to mind when associating with chimneys. However, not many people know that smoke is essentially the language of the flame. Its intentions and behaviors are within the plume of smoke. Should you learn to read it, you may call yourself a fire whisperer.

A bit goes into smoke characteristics with some of its attributes, including color and thickness. So, it can be helpful to learn smoke tips in case of an emergency.

What Exactly is Smoke?

Smoke is a collection of solids suspended in mid-air via lift generated by a flame or high temperatures. It is a combination of aerosols and fire gasses that are toxic, flammable, and volatile. Ultimately, it dictates a flame’s behavior.

Aerosols are a mix of fine solid particles and liquid droplets suspended in the air by another gas. Some natural aerosol examples are fog, mist, dust, clouds, steam, and smoke. Meanwhile, fire gases are the products of combustion — many of them are combustible themselves.

Within these categories, the definitions seem to overlap and can get confusing. Fortunately, we only need to understand that the elements in smoke are dangerous and flammable. This is because they include soot, dust, oils, tars, carbon monoxide, carbon dioxide, hydrogen cyanide, hydrogen sulfide, water vapor, methane, and more.

Smoke is as dangerous as fire. It’s toxic, flammable, suffocating, and irregular. But it can enlighten you on the flame that is producing it. The four attributes used to analyze smoke and its flame are color, speed, volume, and density.

Color

The color of smoke typically ranges from white, gray, tan, and black. A flame’s smoke will regularly transition from white to gray and then to black over time. Tan smoke is a flighty indicator as it may indicate something bad or simply represent the material being used for the flame.

White smoke means the material is off-gassing, which is the releasing of gasses that are absorbed by various materials. White smoke may mean that the fuel material had begun being consumed by the flames. As the last embers of fire die, it will release white smoke, signifying the potential of reignition.

Generally, the darker the smoke, the more volatile the flame. Black smoke is a leading indicator of fire danger. However, carbon-rich materials like rubbers or metals are likely to produce black smoke when burnt. Materials will also start to produce smoke in the later burning stages should they last long enough. Therefore, it is not always a bad sign.

Plastics, paints, or stained surfaces that are used as fuel for a fire will produce gray smoke. This color smoke signifies a proper burn as the flames effectively burn their fuel. Gray smoke should stay this color for most of its burn time. This color can also be indicated that the fire is slowing down as it runs out of fuel.

Dark smoke signifies a hot flame. However, it’s a bit complex because as smoke plumes further from its source, it lightens in color. This means that color cannot be completely trusted as an indicator for gauging a flame’s temperature and activity.

Tan or brown smoke is less common when compared to other colors of smoke. However, when seen, it can indicate that unfished wood products are being used as fuel for the fire. Tan smoke also signifies structural damage but this is not always the case.

Velocity

Smoke’s ability to move is a blessing, more than a curse. Velocity can only be used to measure plumes moving through vents, indicating the pressure inside a building. When outside, smoke is disturbed by the wind and is not focused through a single port. Thus, it spreads as it wishes. However, some attributes of the flame can be ascertained even with this fact.

Only two things can create pressure in an environment for fire: volume and heat. Volume refers to the space smoke is allowed to take up. If the driving force of the velocity is a lack of space in the building, the smoke should quickly slow down in the outside air. Otherwise, the driving force is heat, and the smoke plumes upward quickly before decelerating. This can be used to locate a fire as the smoke will move fastest at the hottest point. If the speed is determined by heat and the smoke is white, the flame is somewhat distant. However, if it is black, it is either close or scorching.

Plumes of smoke that appear to be turbulent can aid in identifying the behavior of smoke. This can almost guarantee a flashover. If the smoke is not turbulent, it is called “laminar” smoke. Laminar smoke is a sign that the container absorbs the heat, making a flashover unlikely.

Flashovers are when all the combustible surfaces in a closed space ignite simultaneously from high thermal radiation. Should the right spark be lit aflame with smoke in the air to carry it, the room may “explode.” Smoke will facilitate a flashover by filling the air with ignition agents and heat.

Smoke may also appear to spin. In these cases, the flame is likely outside and spinning as well. This phenomenon is known as a “fire whirl.” Fire whirls are flames and smoke whirling due to surface winds giving the flame a lateral force while its heat creates lift. Fire whirls are most common during wildfires, especially firestorms, but can be observed in less dangerous flames.

Volume & Density

Volume is the least helpful of the metrics, but it can be helpful when in tandem with the others. A hot clean fire will not release visible smoke. However, a hot quick flame, if not adequately ventilated, will emit light smoke. Damp material will burn slowly and release smoke. The volume of the room with the flame also can affect the amount of visible smoke. Smaller rooms produce more smoke with lighter, smaller fires. Meanwhile, a large room may have a rather sizable fire and light smoke.

The density or thickness of the smoke displays the amount of fuel being used for the fire. Remember, smoke is ignitable and combustible, so seeing an excessive amount of it is a prominent warning that a flame may spread. If laminar smoke is thick enough, it may ignite and spread flames better the thicker it is. With plastics and low-mass material in the mix, flames can catch at lower temperatures.

Author

Tra’Lon Gillis