The term clean agent is defined by NFPA 2001 as an electrically nonconductive, volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation. In addition, the standard illustrates the need to evacuate the room of personnel promptly and prevent re-entry. In all applications, a pressurization relief assessment should be performed to assure pressure created by the release of the substance will not cause damage, Simms says. As for detector selection and system activation, most systems are designed to signal an alarm once a fire is detected, giving facility personnel time to investigate the actual presence of a fire and then override the release of the clean agent in case it was a false alarm. Furthermore, Simms says, fire and smoke detectors that control the release shouldn't be overly sensitive. If they are, it's possible that they could set off a discharge not based on a fire but by what's being detected in the outside air being drawn into a building. You have to be concerned that you re going to make the system too sensitive and set off a release when there is no fire, Simms says. You re trying to set the system to go off only if there really is a fire. If you don't have a fire and the system activates, it's an xpensive release