The two current conceptual approaches to Intrusion Detection methodology are knowledge-based ID systems and behavior-based ID systems, sometimes referred to as signature-based ID and statistical anomaly-based ID, respectively.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the
Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 63.

When you consider top priority tickets for the data center, security, data protection, and power consumption rise to the top. But the one thing that every data center should have, that we often throw on the back burner, is fire protection. Right now, if you heard that your data center was engulfed in flames, you would likely sit in shock, especially if you were not equipped with the proper protection. Fortunately, you can avoid this reality by taking the proper steps to protect your data center.
Dave Admirand, chief data center engineer at PTS Data Center Solutions
(www.ptsdcs.com), says in his own experience, electrical fires are the most common types of fires in data centers. He says, "These are typically caused by electronic equipment failures or failures of the branch circuits powering the data center equipment, including
UPS and air-conditioning equipment-if located in the data center."
So what does the industry offer when it comes to fire detectors and extinguishing systems designed for the data center? According to Ziemba, there is a myriad of different smoke and heat detectors available, and some, he says, are so sophisticated that they can detect-and help extinguish-a fire even before it reaches the incipient, or flame, stage. He says, "Detectors that provide early warning capabilities are very effective in this type of situation. Addressable control panels serve as the brains for the overall fire suppression system in that they receive the signals from the detectors, provide some type of warning to the occupants, and then discharge the system."
The following Reference(s) were used for this question:
http://xtralis.com/resources/article_level1/838/Processor_Editorial_-
_Data_Center_Fire_Protection_January_5x_2007.pdf
and
http://www.interfire.org/features/electric_wiring_faults.asp

Duel gateway host is not considered firewall technology.