Published on September 1, 2017.

Flame Jetting 101

FROM ITS RESEARCH into flame jetting, which it began in 2010, the Fire Research Laboratory at the Bureau of Alcohol, Tobacco, Firearms and Explosives has determined that, while multiple variables can affect whether a flame jet will occur and how long it will be, certain common denominators exist:

1. Almost any necked portable flammable liquid container with a flammable liquid—those with flash points less than 100 degrees F, such as gasoline—can jet. Containers with large openings, such as buckets, cannot jet. In addition to gasoline, common flammable liquids include methanol, ethanol, acetone, and liquor above 150 proof.

2. Flame jetting is typically observed when the container is being tilted and vapors are pouring from the mouth of the container. This allows air to be entrained in the container headspace, diluting the rich fuel vapors in the headspace to within their flammable limits.

3. If the container has a nozzle installed when combustion occurs, flames can travel back into the container. The nozzle restricts expanding gases from venting, resulting in rupture along the container seam. Flames are expelled where the container fails, injuring the person holding the container.

4. If no nozzle is installed when flame jetting occurs, typically the person pouring the container is uninjured and injuries will occur to victims located opposite the container. Frequently there is no thermal or pressure damage to the container.

5. The longest flame jets occur when a container is about one-third full of liquid, regardless of the container’s capacity. This allows for sufficient vapors to accumulate in the head space of the container and for sufficient flammable liquid to be expelled when jetting occurs.

6. In cases involving gasoline jetting, older (weathered) gasoline that has undergone evaporation is more prone to jetting as it releases vapors more slowly than fresh gasoline. This means it can support flame propagation inside the portable flammable liquid container if an ignition source is present and combustion occurs.

7. Flame arrestors (pictured) are highly effective in preventing flame jetting—and typically cost about 50 cents. In ATF testing, no flame jetting was observed in portable flammable liquid containers equipped with flame arrestors.