What is the lower flammable limit of propane?

What is the lower flammable limit of propane?

• A. 1.0%
• B. 2.15%
• C. 3.5%
• D. 4.0%

Answer: (B)

The main idea here is the lower flammable limit, which is the smallest concentration of propane in air that can ignite if there’s an ignition source present. For propane, this boundary sits at about 2.15% by volume in air. That means once the air contains roughly 2.15% propane, ignition becomes possible; below that, the mixture is too lean to support combustion even with a spark or flame. So 2.15% is the value that marks the lower edge of the flammable range. The other numbers aren’t the lower limit because they are either too lean (like 1.0%) or represent mixtures that are already well within the flammable range, not the boundary where ignition first becomes possible.

The main idea here is the lower flammable limit, which is the smallest concentration of propane in air that can ignite if there’s an ignition source present. For propane, this boundary sits at about 2.15% by volume in air. That means once the air contains roughly 2.15% propane, ignition becomes possible; below that, the mixture is too lean to support combustion even with a spark or flame.

So 2.15% is the value that marks the lower edge of the flammable range. The other numbers aren’t the lower limit because they are either too lean (like 1.0%) or represent mixtures that are already well within the flammable range, not the boundary where ignition first becomes possible.