Which type of cylinder must be tested every 3 years according to DOT regulations?

Composite cylinders must be tested every three years according to DOT regulations due to their construction materials and use cases. Composed of various materials like fiberglass and resin, composite cylinders can be lighter and more versatile compared to traditional metal counterparts. However, the nature of these materials requires more frequent testing to ensure their integrity and safety.

The specific testing every three years helps to identify any potential degradation or damage that may occur over time, ensuring that these cylinders remain safe for storage and transport of gases under pressure. It's vital for personnel who work with these cylinders to comply with these regulations to prevent hazards associated with failures or leaks. Other types such as aluminum or steel cylinders generally have different testing and inspection intervals, reflecting their different material properties and typical applications.