Which cylinders are tested at 5/3 service pressure?

The correct answer pertains to DOT3A, 3AA, and 3AL cylinders, which are designed and manufactured for certain standards of strength and safety. These specific cylinders are tested at 5/3 of their service pressure, a practice established to ensure that they can safely handle pressures well above their intended operating limits. This testing method is crucial for ensuring that these cylinders can withstand the rigors of use without failure, especially in emergency situations where reliability is paramount.

In the context of cylinder safety and maintenance, adhering to these testing standards ensures that materials can resist the stresses placed upon them over time and under varying conditions. This creates a higher safety margin, providing peace of mind for users who rely on these cylinders.

Other types of cylinders listed in the options may follow different testing standards and pressures. High-pressure and low-pressure cylinders, as well as fire hose cylinders, each have their own testing protocols specific to their design and intended use. Therefore, the testing pressure for these other cylinder types does not align with the 5/3 standard specifically tied to DOT3A, 3AA, and 3AL cylinders.