We want to install fire detection system in the area where HVAC system is already installed. In case, if we install the fire detection system on roof which is above 1.9 m from cool air supply duct the possibility of activating fire alarm will be lesser however on the either side if we install detectors on the cool air supply duct, then due to air flow possibility smoke dispersion remained there and detector will take higher time to detect .
Recommended space between detector and HVAC duct outlet is not mentioned in NFPA 90 and 72. Can anyone help me to solve this issue.
It will be great ,if any kind of input or suggestion received.