Which gas is typically stored in yellow-coded cylinders?

• A. Oxygen
• B. Helium
• C. Air
• D. Nitrogen

Answer: (C)

Color coding of gas cylinders helps you identify the contents at a glance to prevent dangerous mix-ups. In many coding schemes, yellow indicates compressed air. That means a yellow cylinder contains air—a mix of gases similar to ambient air, compressed and cleaned for use in equipment or testing, rather than a specific pure gas like oxygen or nitrogen. This distinct color helps operators know not to treat it as a supply of a particular therapeutic gas. Always check the cylinder label and local standards, since color codes can vary by country, but the yellow designation is commonly used for air.