If released in a confined space, a liquefied gas may _____________.

• A. Vaporize completely
• B. Condense rapidly
• C. Decrease in volume
• D. Expand to fill the space

Answer: (D)

When a liquefied gas is released, heat from the surroundings causes it to rapidly turn into a gas. The gas form occupies far more space than the liquid, so in a confined area it will quickly spread to fill all available volume. This rapid expansion can displace breathable air and create a serious asphyxiation hazard. That’s why expanding to fill the space is the best description. Condensing rapidly would require cooling the vapor back to a liquid, which isn’t the immediate outcome after release. Decrease in volume isn’t accurate because the gas expands as it forms from the liquid. While some liquid may persist until heat transfer finishes, the dominant behavior in a confined space is rapid expansion to fill the space.