Which gas has the largest explosive range in air among common welding fuels?

Which gas has the largest explosive range in air among common welding fuels?

• A. Acetylene
• B. Hydrogen
• C. Propane
• D. Butane

Answer: (A)

Understanding flammable range in air: a gas will ignite only when its concentration in air lies between its lower and upper explosive limits. Acetylene has the widest range among common welding fuels, meaning it can ignite over the broadest mix of air and gas. In practice, acetylene can burn in air from roughly 2.5% up to about 80% acetylene in the mixture, with the rest being air, giving a wide window for ignition. This broad span comes from its combustion chemistry and fast flame propagation, which allow flame to sustain itself across both quite lean and moderately rich mixtures. Hydrogen also has a wide range but not as broad as acetylene; propane and butane have narrower ranges because they require higher oxygen content to burn.

Understanding flammable range in air: a gas will ignite only when its concentration in air lies between its lower and upper explosive limits. Acetylene has the widest range among common welding fuels, meaning it can ignite over the broadest mix of air and gas. In practice, acetylene can burn in air from roughly 2.5% up to about 80% acetylene in the mixture, with the rest being air, giving a wide window for ignition. This broad span comes from its combustion chemistry and fast flame propagation, which allow flame to sustain itself across both quite lean and moderately rich mixtures. Hydrogen also has a wide range but not as broad as acetylene; propane and butane have narrower ranges because they require higher oxygen content to burn.