Manifolds for gas cylinders shall consist of two equal headers; each with one average day's supply, but not fewer than how many connections?

• A. three
• B. two
• C. four
• D. one

Answer: (B)

Redundancy and uninterrupted supply in a gas-cylinder distribution manifold are the key ideas here. When a manifold has two equal headers, each header supplies one average day’s worth of gas. To keep the system fed even while changing cylinders or isolating a line, you need more than a single connection per header. Having not fewer than two connections per header provides the necessary flexibility to attach or detach cylinders or branch lines without shutting off the entire flow, preserving continuous service. That minimum of two connections per header is why the correct choice is two. Additional connections beyond the minimum are possible but not required by this specification.