It is common for sprinkler heads in residential buildings to be of the concealed type. Key parameters for the thermal sensitivity of sprinkler heads are the response time index (m^½s^½) and conductivity factor (C factor, m^½s^−½). BS 9252:2011 and BS EN 12259-14:2020 outline test methods to determine whether sprinkler heads achieve adequate thermal sensitivity, stipulating that a room test be undertaken for concealed heads. In carrying out this test, neither the response time index nor C factor is defined. This paper uses computational modelling tools Fire Dynamics Simulator and B-RISK to simulate the room test. In running these simulations, maximum values for the ‘effective’ response time index and C factor needed to pass the room test can be estimated, assuming concealed heads can be represented as equivalent pendent heads. Initial deterministic simulations are used to calibrate results between Fire Dynamics Simulator and B-RISK. Monte Carlo modelling is then utilised within B-RISK, with variable parameters for the response time index and C factor (C), to estimate the relationship between the two parameters necessary to pass the room test. As a result, it is proposed that this relationship can be represented using a simple, empirical power law equation of response time index = 100 (5.4–C)^2/3, where C < 5.4.

Practical application: The results indicate that the minimum RTI and C factor values needed to pass the room test are greater than those needed to pass wind tunnel testing methods. In observing that equivalency is not demonstrated by the room test, and by defining the RTI/C factor relationship needed to pass the test, this paper provides fire safety engineers with amended values for concealed heads to be adopted in future assessments. In the absence of any detailed specification for sprinkler heads, it is recommended that an RTI of 290 m^½s^½ and a C factor of 0.5 m^½s^−½ may be applied.

住宅建筑中的喷头通常是隐藏式的。对于喷头的热灵敏度的关键参数是响应时间指数（米^½小号^½）和导热系数（C因子，米^½小号^-½）。BS 9252：2011和BS EN 12259-14：2020概述了确定洒水喷头是否达到足够的热敏性的测试方法，规定对暗装喷头进行室内测试。在进行该测试时，没有定义响应时间指标或C因子。本文使用计算模型工具Fire Dynamics Simulator和B-RISK来模拟房间测试。在运行这些模拟时，假设隐蔽的头部可以表示为等效的悬垂头部，则可以估算出通过室内测试所需的“有效”响应时间指数和C因子的最大值。初始确定性仿真用于校准Fire Dynamics Simulator和B-RISK之间的结果。然后在B-RISK中使用蒙特卡洛建模，并为响应时间指标和C因子（C）使用可变参数，估算通过室内测试所需的两个参数之间的关系。结果，建议可以使用响应时间指数= 100（5.4–C）的简单经验幂定律方程来表示这种关系。^2/3，其中C <5.4。

实际应用：结果表明，通过室内测试所需的最低RTI和C系数值大于通过风洞测试方法所需的最低RTI和C系数值。为了观察室内测试并不能证明其等效性，并通过定义通过测试所需的RTI / C因子关系，本文为消防安全工程师提供了隐藏头的修正值，以便将来进行评估。在不存在用于喷头任何详细的说明书的，则建议为290μm的RTI ^½小号^½和0.5μm的一个C因子^½小号^-½可以被应用。