Performance evaluation of limited area sprinkler systems in large-scale burn experiments

Many existing high-rise buildings remain non-sprinklered and highly vulnerable to fires. The limited area sprinkler system is a partial sprinkler system which can be used as a retrofit to existing high-rise buildings based on NFPA 101 (2021), balancing cost and safety. It provides a practical, effective, and economical fire protection solution for existing buildings where a complete retrofit is challenging due to costs, structural constraints, or historical preservation concerns. This study investigated the performance of a limited area sprinkler system by two large-scale burn tests. It compared two dwelling unit protection approaches provided by NFPA 101 (2021), Section 31.3.5.6.2: a single sprinkler above the unit entry door versus a 20-minute fire-rated entry door. Temperatures and radiant heat flux were recorded, with tenability criteria defined by thresholds of 80 °C (176 °F) and 2.5 kW/m² at human head level. The limited area system maintained the corridor tenable in both burns. In terms of protecting the interior of the dwelling unit, the sprinkler strategy controlled the temperatures significantly lower than the fire door strategy at human head level. In conclusion, even partial sprinkler coverage markedly improved life safety by preserving egress tenability and limiting fire spread and damage. These findings underscore the life safety benefits of the limited area system, informing building code compliance and retrofit strategies.