Final answer:
SCBA air cylinders made of aluminum or steel typically require testing every five years. The testing frequency for composite cylinders may differ. Organizations should consult the manufacturer's guidelines and relevant industry regulations.
Step-by-step explanation:
The question pertains to SCBA (Self-Contained Breathing Apparatus) which are safety devices used by firefighters and in industrial applications. SCBA air cylinders that require testing every five years are the ones made of aluminum or steel (typically these are the traditional metal cylinders). Composite cylinders such as those made of fiberglass, carbon fiber, or a combination of materials, may have different testing requirements based on their design and materials. However, the frequency of testing can also depend on specific industry standards and regulations, so it's important for organizations to refer to the guidelines provided by the manufacturer and regulatory bodies like the Department of Transportation (DOT) or Occupational Safety and Health Administration (OSHA) in the United States.