Diameter Index and Safety System (DISS) is designed to ensure gas types have their own pitch and size and are not interchangeable.

• A. It regulates cylinder pressure
• B. It ensures each gas type has its own pitch and size and is not interchangeable
• C. It indicates cylinder contents by color
• D. It ensures all gas cylinders have identical connectors

Answer: (B)

The main concept being tested is how the Diameter Index and Safety System prevents interchange of gases by giving each gas type a distinct connector pitch and size. DISS uses different diameters and thread pitches for the outlets and fittings of various medical gases so that a hose, regulator, or valve for one gas cannot physically mate with another gas line. This design minimizes the risk of delivering the wrong gas to a patient or device, which is a critical safety measure in medical gas systems.

It’s not about regulating cylinder pressure—that’s handled by regulators and valve design—nor is it solely about color coding, which serves as a visual cue but doesn’t prevent misconnection. And having identical connectors would undermine safety, which DISS specifically avoids by ensuring each gas type has unique dimensions.