|FIRE DETECTION STRATEGIES|
|Aspirating Smoke Detection|
|FIRE SUPPRESSION SYSTEMS|
|Clean Agent Suppression|
Fire can threaten the business and human life, and smoke and water can also take their toll, causing devastating damage. The 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 through which three conditions are met:
- Identify the presence of a fire
- Communicate the existence of that fire to the occupants and proper authorities
- Contain and extinguish 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.
To protect a mission critical facility, addressable early warning smoke detectors and heat detectors connected to a fire panel can be an option. Addressability means that each of these detectors can indicate its specific position, or “address,” enabling the fire department or monitoring station to know precisely which device has gone into alarm. Having the exact location is important for quickly identifying and responding to emergencies.
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 these 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 to detect a broad range of fires quickly would be a multi-criteria 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 uses a focused, laser-based source to achieve sensitivities that are 100 times more sensitive than standard addressable or conventional infrared-based photoelectric smoke detectors. They are designed to respond to incipient fire conditions as low as 0.02% per-foot obscuration to provide valuable time for personnel to investigate the affected area and take appropriate action to mitigate risk.
Some can automatically compensate for changes in the environment, such as humidity and dirt buildup. They can also 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.
Aspiration smoke detectors (ASDs) provide high-sensitivity detection, and one of the most common applications for ASDs has been server rooms and data processing facilities. In these facilities, every second of downtime accrued, every transaction missed, and every byte of data destroyed due to smoke or fire can mean significant financial losses.
The protection of data facilities is complicated by the fact that the potential for smoke and fire is heightened as the electrical equipment they contain creates a high-heat-density environment. At the same time, air conditioning (A/C) devices used to control the temperature create a high airflow, and air filters used by the A/C units can remove smoke particulate, making detecting smoke in a data center extremely challenging.
To fully protect a data center from smoke and fire damage, a system capable of achieving very early warning fire detection in a high airflow environment is a must.
ASDs overcome the challenges of protecting data centers by actively sampling air through a network of pipes, which can be run above the ceiling; under the floor; in-between, in, and above server racks and cabinets; and in the return air duct of an air-handling unit — anywhere smoke might travel.
All that is visible in each protected room, if at all, are the tiny openings of the pipes that sense the smoke. The base unit of the ASD typically resides in a separate room where it can be monitored for activity. This base unit, which is networked through the fire panel, provides visual status indicators and can be programmed to instantly issue warnings to pre-specified individuals. In contrast to spot smoke detectors, ASD pipes can withstand extreme environments, such as cold storage units or areas that need to be completely washed down.
With some ASD technology delivering smoke sensitivity as low as 0.00046% per-foot obscuration, these detectors are capable of providing very early warning fire detection. This level of sensitivity, combined with multiple levels of alert, enable facilities to implement a strategic response plan. Appropriate personnel can address incipient fire conditions before costly damage and downtime can occur.
A newer innovation that can further benefit data center applications is increased nuisance immunity. Traditionally, some facilities had to learn to live with false alarms as the cost of using a high-sensitivity aspirating detector. However, more advanced detection and filtering technology has greatly enhanced the nuisance immunity of some ASDs. This keeps the ASDs from going into alarm for non-emergencies such as dirt build-up.
FIRE SUPPRESSION SYSTEMS
Although smoke detectors primarily alert for a fire condition, in a mission critical 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 utilized.
Sprinkler systems, which are designed specifically for protecting the structure of the building, can be installed in four different configurations: wet-pipe, dry-pipe, deluge, and pre-action. The wet-pipe 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 is not ideal either for mission critical facilities.
A pre-action system is, however, commonly installed in a mission critical facility.
“A pre-action sprinkler system is one effective alternative because of its dual action criteria,” says 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 pre-action valve that prevents the pipes from filling with water during normal times. This valve is held closed electrically, only being released by activation of the detection system (fire detectors) 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 will now function 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 suppression agent 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.
In addition to sprinkler systems, clean agent 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 1230™, (DuPont) FM-200™, or (Ansul) Inergen. They combine the benefits of clean agent systems and active fire protection with people-safe, clean, environmentally friendly performance,” explains Eric Fournier, project manager, 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,” says 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 continues, “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 mission critical system remains: to minimize or prevent a fire event in order to maintain constant operation and protect occupants.
Aspiration Detection Provides Earliest Possible Warning for Cyber Innovation Center’s Server Room
Because aspiration detection systems (ASDs) sense even trace amounts of smoke long before a fire breaks out and long before other detectors recognize the danger, many mission critical facilities now insist on their use.
Frank Gardner, project manager of the fire alarm/special hazards department for Fire Tech Systems, Inc. in Shreveport, LA, has been a big proponent of very early warning fire detectors, specifically ASDs, for his customers’ installations. “Most of the time, aspiration detection is used when the customer wants the earliest possible warning of a fire incident,” he says.
“It’s really the need for early detection of a fire situation that plays into the critical nature of protecting our customers’ assets and equipment,” Gardner continues. “Aspiration has found its niche in the protection of mission critical information or equipment and irreplaceable items.”
Protecting data used to be the primary concern, Gardner explains. Now as offsite data storage has become common practice, the protection of data is less of a concern than the equipment itself.
That has been the case for one of Fire Tech’s aspiration detection clients: the Cyber Innovation Center in Bossier City, LA. “When we started designing this system,” says Gardner, “our major concern was addressing its need for early warning. You don’t want to lose a whole rack of equipment before you know there is a fire.”
Gardner says that Cyber Innovation’s 5,400-sq-ft server room was unique in that they were using a hot aisle and cold aisle design. This posed challenges because the cold aisles were separated from the hot aisles by heavy plastic sheeting, creating a separate enclosure for each cold aisle (Figure 1).
“We had to take that into consideration during the design because of the pressure difference between the hot and cold aisles,” he says, noting that System Sensor’s FAAST Fire Alarm Aspiration Sensing Technology® fit their requirements. “Because FAAST constantly monitors for high and low air flow conditions, we opted to use four devices — two for the cold aisles and two for the hot aisles — with a total of 45 sampling points in the server room” (Figure 2).