Ordinary classification corresponds to a maximum ceiling temperature of?

• A. For temperatures up to 225°F (107°C)
• B. For temperatures up to 300°F (149°C)
• C. For temperatures up to 170°F (77°C)
• D. For temperatures up to 200°F (93°C)

Answer: (C)

The key idea is that ordinary classification is tied to the maximum ceiling temperature the system is expected to handle. In NFPA 13R for low-rise residential buildings, ordinary environments assume ceilings won’t exceed 170°F (77°C). Sprinklers selected for ordinary classification are rated to operate reliably up to that temperature, which matches typical living-space conditions. If the space could reach higher ceiling temperatures, you’d use sprinklers rated for those higher temperatures (such as 225°F or 300°F), which are not part of the ordinary classification.