The flammable range

The flammable range

• A. Becomes smaller as pressure decreases
• B. Becomes larger as pressure increases
• C. Remains unchanged with pressure
• D. Only occurs at high temperatures

Answer: (B)

Flammable range is the span of fuel concentrations in air that will ignite when an ignition source is present. When pressure goes up, more fuel molecules are packed into the same space, so ignition becomes possible over a wider mix of concentrations. In other words, the lean side (lower fuel content) becomes capable of ignition sooner, and the rich side (higher fuel content) remains ignitable over a broader range as well. That combination means the overall flammable range broadens with increasing pressure. If pressure drops, the range tightens because fewer fuel-air mixtures are capable of sustaining ignition. It’s not tied to high temperature alone, and it does change with pressure, so it isn’t unchanged or limited to only high temperatures.

Flammable range is the span of fuel concentrations in air that will ignite when an ignition source is present. When pressure goes up, more fuel molecules are packed into the same space, so ignition becomes possible over a wider mix of concentrations. In other words, the lean side (lower fuel content) becomes capable of ignition sooner, and the rich side (higher fuel content) remains ignitable over a broader range as well. That combination means the overall flammable range broadens with increasing pressure. If pressure drops, the range tightens because fewer fuel-air mixtures are capable of sustaining ignition. It’s not tied to high temperature alone, and it does change with pressure, so it isn’t unchanged or limited to only high temperatures.