What happens to a propane/air mixture containing less than 2.15% gas?

A propane/air mixture containing less than 2.15% gas is considered too lean to burn. Lean mixtures have a lower concentration of fuel, in this case propane, compared to air, which means there is not enough propane present to support combustion. For a combustion reaction to occur, a certain ratio of fuel to oxygen is necessary to achieve ignition and stable burning conditions. If the propane concentration falls below this threshold, there isn’t sufficient fuel to sustain the combustion process, leading to the conclusion that it is too lean to burn efficiently.

In contrast, a mixture that is too rich would have an excess of propane compared to the available oxygen, which typically can lead to incomplete combustion. Therefore, understanding the proper fuel-air mixture ratios is crucial in determining combustion behavior.