It is critical to distinguish between Smoke Detectors and Heat Detectors regarding their installation distances, as each follows a different methodology according to NFPA 72:
1. Smoke Detectors: These do not rely on a "Listed Spacing." Instead, they adhere to the Nominal Spacing defined by the standard, which is 9.1 m (30 ft). This baseline value is used as the starting point, and then code-specific requirements for installation conditions and spacing adjustments are applied.
2. Heat Detectors: These rely exclusively on the Listed Spacing specified in the manufacturer’s technical data sheet. The listed spacing value must be obtained first, and then Table 17.6.3.5.1 is used to apply the necessary Reduction Factor to determine the final allowable spacing before commencing the layout and distribution.