CNG in its purest form is methane which has a flammability range of ______% - ______%

CNG in its purest form is methane which has a flammability range of ______% - ______%

• A. 5 to 15 percent
• B. 0 to 5 percent
• C. 15 to 40 percent
• D. 1 to 10 percent

Answer: (A)

The key idea here is flammability limits: a fuel-gas like methane will burn only if its concentration in air falls within a certain window. If there’s too little methane, the mixture is too lean to ignite; if there’s too much, it’s too rich to ignite. This creates a distinct, relatively narrow range where combustion is possible. The correct choice captures that idea by describing a moderate, bounded window for when methane can burn in air—neither too lean nor too rich. The other options would imply ignition outside that realistic window (either right at zero concentration or extending into ranges where methane cannot sustain flame), which doesn’t match how methane behaves in air. So the correct option reflects methane’s characteristic flammability window.

The key idea here is flammability limits: a fuel-gas like methane will burn only if its concentration in air falls within a certain window. If there’s too little methane, the mixture is too lean to ignite; if there’s too much, it’s too rich to ignite. This creates a distinct, relatively narrow range where combustion is possible.

The correct choice captures that idea by describing a moderate, bounded window for when methane can burn in air—neither too lean nor too rich. The other options would imply ignition outside that realistic window (either right at zero concentration or extending into ranges where methane cannot sustain flame), which doesn’t match how methane behaves in air. So the correct option reflects methane’s characteristic flammability window.