What are DOT cylinders commonly used for?

DOT cylinders, or Department of Transportation cylinders, are specifically designed and regulated for the safe transport and storage of gases, including but not limited to propane. Propane is commonly utilized in various applications such as fueling grills, heating systems, and other domestic and industrial tasks. The construction and safety features of DOT cylinders make them suitable for storing propane under pressure, ensuring that the gas can be handled safely and effectively.

In the context of the other options, while DOT cylinders could technically be used for different purposes, they primarily serve the function of containing pressurized gases like propane. The regulation and design standards for DOT cylinders focus on scenarios involving compressed gases, which aligns closely with the use of propane. Therefore, this answer reflects the practical application of DOT cylinders in everyday life and industry.