The Promise (and the Pain) of Networked Fire Detection
Fire detection has made tremendous strides during the past decade, just as home local area network (LAN) technology has blossomed. While these concurrent advances have created an exciting proliferation of network technology in the fire/life-safety industry, resultant growth and high expectations are often cause for misunderstanding and disappointment for end users and installers alike.
There are multiple degrees of network involvement when it comes to command, control and occupant notification. Where IP video cameras can be connected to a client’s home LAN, this is not typically the norm with fire alarm detection devices. So, when fire equipment manufacturers speak of using network technology in proprietary fire detection systems, this most often does not include LAN capability.
Common computer network technology may very well become the de facto method of connection between fire alarm sensors and the fire alarm control panel (FACP). Should that convergence come to fruition, fire alarm installers will simply connect their smoke and heat detectors, manual pulls, output modules and other devices to the nearest hub or switch.
Just think of the savings in money and effort that could be realized should that day arrive. No longer would it be necessary to use dedicated fire alarm circuits. Installers would merely connect their fire devices to the LAN. This would likely take the same form as today’s network-based access control technology where devices connect to individual controllers, which themselves are merely nodes on a large LAN.
We will take a look at present-day enterprise-grade fire alarm systems, the role network technology plays in the inner workings of these systems and how a typical fire alarm network currently operates in conjunction with the LAN. We’ll also consider what the industry must do in order to bridge the gap between the proprietary fire alarm network of today and the home LAN-based fire alarm system of tomorrow.
Why Current Network Technology Doesn’t Work for Fire Detection
Technically speaking, in this day and age of computerization it is certainly possible to operate a fire alarm system on a home LAN. In fact, many aspects of LAN methodology are employed in numerous enterprise-grade fire systems made today. Despite this fact, there are several reasons why fire alarm detection devices do not yet use the LAN to transport alarm, supervisory and trouble signals to the head-end or FACP.
“Fire alarm manufacturers could easily implement Ethernet-based fire alarm networks this very day, but the problem is when you talk about fire there are lots of obstacles that must be considered,” says Mario Casamassima, vice president of engineering with Gamewell-FCI of Northford, Conn., a Honeywell company.
The most fundamental reasons include:
- General lack of supporting codes and standards by code-making bodies
- Common reluctance by third-party testing laboratories to sign onto network use for a variety of reasons
- Many code enforcement officials continue to see fire alarm technology in a more traditional sense
- Today’s network technology is not capable of meeting the rigorous requirements associated with modern fire alarm systems
As any veteran fire alarm technician can tell you, the fire alarm business revolves around fire codes, standards and the willingness of fire alarm companies to use code-compliant equipment. But unless all the key code- and standard-making bodies agree, nothing will change.
“Because of the codes and standards established by the National Fire Protection Association [NFPA], FM Global [FMG], and Underwriter’s Laboratory [UL], today’s [computer] network cannot be used for detection, notification or command functions,” says Casamassima.
This explanation alone accounts for 75 percent of the reason why fire detection has yet to use the traditional LAN for signal transport. The other 25 percent involves the inability of traditional network technology and its associated hardware to accommodate the fire protection process in a code-compliant manner.
Today’s Fire Alarms Require Survivability and Code Compliancy
The key issue at the center of placing fire detection on the LAN is survivability. Survivability relates to a general hardening of a fire alarm system’s physical defenses and the implementation of electronic monitoring to ensure functionality during events that could render a system inoperable.
“Survivability is driving the fire industry to network technology where distributed intelligence assures continued functionality during a catastrophic event,” says Casamassima. “Because NFPA 72 specifically calls for enhanced survivability, the authority having jurisdiction [AHJ] has every right to require this feature in the systems they approve.”
One of the problems with current network technology is the unshielded twisted pair (UTP) Category-5, -5e and -6 cable that commonly connects multiple nodes to the head-end.
In this regard, today’s LAN does not comply with the requirements set forth for cable in NFPA 72, Section 188.8.131.52.14 where it calls for the continued operation of a fire alarm system during fault conditions: “Interconnection means shall be arranged so that a single break or single ground fault does not cause an alarm signal.”
By contrast, enterprise-grade fire alarm systems are designed to meet Style 6 and 7 as required in Table 6.6.1 of NFPA 72, 2007. In this case, no matter what fault takes place on the signaling line circuit (SLC), local notification is assured using either style configuration. Using Style 6, alarm receipt capability is required on a single open, single ground, and an open with a ground condition. Using Style 7, alarm receipt capability is required on the above conditions as well as a wire-to-wire short.
Also, today’s LAN does not provide ample code-compliant warning — either locally or remotely — when a problem occurs.
According to Section 184.108.40.206 of NFPA 72, 2007 Edition: “Unless otherwise permitted or required by 220.127.116.11.1 through 18.104.22.168.13, all means of interconnecting equipment, devices, and appliances and wiring connections shall be monitored for the integrity of the interconnecting conductors or equivalent path so that the occurrence of a single open or a single ground-fault condition in the installation conductors or other signaling channels and their restoration to normal shall be automatically indicated within 200 seconds.”
Fire alarm systems must be able to guarantee something will happen in a given time frame when an alarm signal is received, says Casamassima. “Fire alarm manufacturers must be able to predict how long an event will take to clear the system and control something,” he says. “Unfortunately, at this time this is not possible with a standard home LAN.”
The physical characteristics of the network Cat-5, -5e and -6 cable is not the only problem that fire alarm installers have to consider when they marry their fire detection system to a home LAN. “If you tie a PC to a head-end network router in an office [LAN] environment you will have a centralized closet somewhere no more than 350 feet away,” Casamassima says.
“In the fire business, we have to deal with horizontal and vertical wire runs and you may have thousands of feet between nodes. How can network technology [as it is today] successfully deal with that?”
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