Open head sprinklers vs close head sprinklers: what is the difference when activated?

• A. Open: all heads spray when activated
• B. Open: only heads opened by heat spray
• C. Close: all heads spray when activated
• D. Close: Only heads opened by heat will spray

Answer: (A)

The key idea here is how sprinkler head design determines where water goes when the system starts. Open-head sprinklers have every head connected and ready to release water; when the system is activated, water flows to all heads, so every sprinkler sprays. This is typical of deluge/open-head configurations where there’s no head-by-head heat-triggered closure blocking water. In contrast, closed-head sprinklers use heat-sensitive seals at each head, so water is held back at each head until its own heat threshold is reached; only the heated heads spray, and others stay dry until heated. So the correct understanding is that open heads spray all heads when activated, matching the behavior of open-head systems.