Aspirating Smoke Detection — Many air sampling smoke detectorscan also 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% per-foot obscuration. This type of detection provides advanced notification so facility managers or other appropriate personnel 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, E-mail updates can be sent to appropriate personnel 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.
For example, when it came to building Per Mar Security Services’ new $500,000 500-square-foot datacenter in Davenport, Iowa, the aspiration system was programmed to send a signal to the central station alerting of a pre-alarm condition if the aspiration unit detects an early warning alert.
“It gives the early warning or very early warning depending on how you configure it and can actually check into a problem before it actually arises,” says Per Mar CIO Daniel Turner, “which absolutely is beneficial to the datacenter.”
Fire Suppression System Options
Although smoke detectors primarily alert of 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. Now let us look more closely at the two main categories in this area: sprinkler and clean agent systems.
Sprinkler Systems — 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 wate
r 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 dual action criteria,” says Ramzi Namek, director of engineering for Total Site Solutions in Columbia, Md. “The pipe remains dry until the fire detection system activates a control valve [located outside the datacenter to avoid damage from leaks], filling it with water.”
