What happens when a propane/air mixture contains less than 2.15% propane?

When a propane/air mixture contains less than 2.15% propane, it is considered too lean to burn. Combustion requires a specific proportion of fuel and air to sustain a flame, and when the concentration of propane falls below this threshold, there is insufficient fuel to support continuous combustion. This lean mixture lacks the necessary fuel for the combustion process, resulting in ineffective ignition and an inability to maintain a flame.

In terms of combustion science, a lean mixture occurs when the fuel-to-air ratio is too low, meaning there isn't enough fuel present to react with the available oxygen in the air. Below the lower explosive limit (LEL), which for propane is approximately 2.15%, the combustion reaction cannot be sustained, leading to extinguished flames and risk of incomplete combustion rather than an explosion.

Understanding this concept is crucial for safety in handling propane, as ensuring the right mixture allows for controlled burns and prevents potential hazards associated with combustion.