Here we have a sprinkler water flow device activating at about 30 seconds. Here is a quote from the NFPA. Basically, activation of the fire alarm shall occur within 90 seconds of the flow of water. It shouldn’t occur immediately within the flow of water to prevent false alarms.
5.10.2* Initiation of the alarm signal shall occur within 90 seconds of waterflow at the alarm-initiating device when flow occurs that is equal to or greater than that from a single sprinkler of the smallest orifice size installed in the system.
