Sophisticated and Strategic

To protect information assets, a fire protection strategy must incorporate specific emergency identification and suppression alongside detection

• By Kris Cahill
• Mar 01, 2012

Mission-critical facilities such as data and telecommunications centers must maintain operations without interruption. Mission continuity is ensured for facilities through the use of redundant power supplies and mechanical systems and cuttingedge fire protection systems.

Fire in these facilities obviously can threaten the business and human life. Key to defending against a catastrophe is a sophisticated fire protection system that integrates seamlessly with the entire environment.

Fire protection for mission-critical facilities can be complex and daunting. System designs should be based on a total fire protection approach in which three conditions are met: identifying the presence of a fire, communicating the existence of that fire to the occupants and proper authorities, and containing and extinguishing the fire, if possible. Being familiar with all technologies associated with fire detection, alarming and suppression is important to developing a sound fire protection solution.

Fire Detection Strategies

There are many ways of detecting and suppressing fires, but only a few should be used for mission-critical applications. For example, the main goal of the fire protection system in a data center is to get the fire under control without disrupting the flow of business or threatening occupants.

Spot Detection

For the purposes of protecting a mission-critical facility, addressable early-warning smoke detectors and heat detectors can be an option. Because the airflows are rapid in an area such as a data center, it is important to realize the differences between types of detectors.

Ionization smoke detectors are quicker at detecting flaming fires, such as those commonly found in chemical storage areas, rather than slow, smoldering fires that most typically occur in data centers and telecom equipment spaces. Ionization sensors almost immediately recognize fires characterized by combustion particles from 0.01 to 0.3 microns. However, ionization sensors offer limited or slower capabilities when installed in areas with high airflow, which is often the case in mission-critical environments.

Photoelectric smoke detectors, however, quickly respond to smoldering fires characterized by combustion particles from 0.3 to 10.0 microns, making these detectors more appropriate for most mission-critical settings.

One solution for detecting a broad range of fires quickly would be a multicriteria detector that uses photoelectric particulate detection in tandem with sensors that detect other products of combustion, such as carbon monoxide (CO) and light (infrared). Together, these signals are cross-referenced by an onboard microprocessor that uses algorithms to “process out” false alarms while enhancing the response time to real fires.

Another solution is to use intelligent high-sensitivity detectors, which are very similar to standard detectors except that they employ a more highly advanced detection method.

High-sensitivity spot detection typically employs a focused laser-based source to achieve sensitivities that are 100 times more sensitive than standard addressable or conventional infraredbased photoelectric smoke detectors. They are designed to respond to incipient fire conditions as low as 0.02 percent per foot obscuration to provide valuable time for staff to investigate the affected area and take appropriate action to mitigate risk.

These detectors are addressable and able to send information to the central control station, thereby pinpointing the exact location of the smoke. Some can automatically compensate for changes in the environment, such as humidity and dirt buildup. They also can be programmed to be more sensitive during certain times of the day. For instance, when workers leave the area, sensitivity will increase.

High-sensitivity detectors are commonly placed below raised floors, on ceilings and above drop-down ceilings, as well as in air-handling ducts to detect possible fires within the HVAC system.

Aspirating Smoke Detection

Many air-sampling smoke detectors also can provide high-sensitivity detection. Some systems can be up to 1,000 times more sensitive than a standard photoelectric or ionization smoke detector and are capable of detecting byproducts of combustion in concentrations as low as 0.00046 percent per foot obscuration. This type of detection provides advanced notification so facility managers or other appropriate staff can intervene and take action before a combustion event becomes disastrous.

An aspiration system works by drawing in smoke through a network of piping via the aspirator (fan). The air sample is then passed through a filter and into the sensing chamber of the detector. Using advanced sensing technology, the detector analyzes the air sample and sends a signal of airborne smoke intensity to a remote or integrated display module and a fire detection panel, when necessary, to raise an alarm.

These detectors communicate information to a fire alarm control panel, a software management system or a building management system through relays or another interface. With some systems, email updates can be sent to appropriate staff to communicate alarm levels, urgent or minor faults or other status conditions via relays. The multiple warning levels of this system can trigger different responses at different stages of a fire, from controlling air conditioning to suppression release. To accommodate specific codes or environments, alarm relays can be set with 0- to 60-second delays.

Fire Suppression Systems

Although smoke detectors primarily alert of a fire condition, in a missioncritical facility they may also be used to control the release of fire suppression systems. Should a fire occur, suppression systems are the next line of protection and can quickly extinguish the fire with minimal or no effect on the operation. It is important to consider the suppression system to be used.

Sprinkler Systems

Sprinkler systems, which are designed specifically for protecting the structure of the building, can be installed in four different configurations: wet-pipe, drypipe, deluge and pre-action. The wetpipe system consists of a piping system connected to a water source and filled with water so that water discharges immediately from sprinklers activated by a fire. In general, wet-pipe sprinklers are not recommended for mission-critical facilities; however, depending on local fire codes, they may be required.

A dry-pipe system is typically used in areas subject to freezing and consists of piping connected to a water source and filled with air pressure supplied by a compressor. When a sprinkler is activated, the air is expelled first, allowing a special check valve, called a dry-pipe valve, to operate. This allows water to flow into the piping and out any open sprinklers. This, too, is not ideal for mission-critical facilities.

A pre-action system is more common in a mission-critical facility. “A pre-action sprinkler system is one effective alternative because of its dualaction criteria,” said Ramzi Namek, director of engineering for Total Site Solutions, Columbia, Md. “The pipe remains dry until the fire detection system activates a control valve (located outside the data center to avoid damage from leaks), filling it with water.”

It consists of closed-type sprinkler heads connected to a series of piping arrangements. The system has a preaction valve that prevents the pipes from filling with water during normal times. This valve is held closed electrically by activation of the detection system (fire detectors) being released only when an electrical signal is sent to the releasing solenoid valve. Upon receipt of the signal, which could be from any of the sensors attached to the system, an electrical mechanism opens the pre-action valve, and the pipelines fill with water under pressure. The system at that point functions as a standard wet-pipe system. The water tanks are located away from the area but are readily accessible.

“Another important design consideration to plan for is space for suppressionagent tanks. Some suppression agents are stored in gas form; others are stored as a liquid, which can impact the number and size of tanks required,” explains Namek.

Clean-agent Suppression

In addition to sprinkler systems, cleanagent suppression systems can extinguish fires in their incipient stage, well before enough heat builds in a room to activate a sprinkler system. When activated, these waterless flame-suppression systems discharge as a gas. The gas reaches all areas of the protected facility and leaves no residue to damage sensitive equipment or require costly cleanup. Clean agents suppress fires by many methods, including depleting the area of oxygen, interrupting the chemical reactions occurring during combustion, and absorbing heat.

“Clean-agent systems typically use [3M] Novec 123, [DuPont] FM-20, or [Ansul] Inergen. They combine the benefits of clean-agent systems and active fire protection with people-safe, clean, environmentally friendly performance,” said Eric Fournier, project manager at Total Site Solutions.

Clean-agent suppression systems, protecting both the areas underneath and above the raised floor, are the most common method of fire protection for Class C electrical hazards. “Raised floors bring up some important issues with regard to fire protection in mission- critical facilities,” said Fournier. Spaces beneath raised floors often experience many air changes per hour, which presents a difficult detection design.

“Because raised floors create a completely separate plenum and pose as much of a fire hazard as the numerous pieces of computer equipment situated on the raised floors,” Fournier said, “they must be protected with the same level of fire protection as the space above.”

These clean-agent suppression systems, when controlled by an interface with a high-sensitivity smoke detection system, suppress fires without damaging IT equipment and allow staff to get the facility up and running faster.

Regardless of which detectors or systems are used in the fire and life safety design in a mission-critical facility, all must be networked into one central location. Whether that is a series of panels or a control center, there will be a vast amount of equipment used—hundreds and maybe thousands of devices, depending upon the size of the facility. Programming is the key to how well all the pieces come together. The outcome for a fire and life safety system within a missioncritical system remains to minimize or prevent a fire event in order to maintain constant operation and protect occupants.

This article originally appeared in the March 2012 issue of Security Today.