Acetylene is categorized as a __________ gas.

Acetylene is categorized as a flammable gas. This means that it can easily ignite and burn when exposed to an ignition source, such as a spark or flame. Acetylene is commonly used in welding and cutting processes due to its high flame temperature. The fact that it's highly flammable makes safety precautions essential when handling and storing it to prevent accidental ignition and fires.

In contrast, non-flammable gases do not ignite under standard conditions, toxic gases pose health risks upon exposure, and inert gases do not react with other substances easily. Understanding these distinctions is crucial for safe operations involving gases in various applications.