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New advances in fire detection technology are making fire protection systems less intrusive in historic buildings. Air sampling, or aspirating, fire detection systems represent new technology that can offer increased protection by providing earlier detection and a potential to reduce the physical and aesthetic impact of fire protection upgrades in historic buildings.
Air sampling systems consist of small components which can be installed with minimal visual and structural impact. The small sampling tubes used to collect air can be concealed in unobtrusive places like light fixtures, ledges, or ornamental ceilings, which make these systems good choices for historic properties.
Since air sampling systems are generally costlier than conventional detection systems, and have limitations, at this time their use in NCR public buildings is best limited to particular spaces where their capabilities offer exceptional benefits in reduced visual impact or damage to ornamental finishes. Consider use for large spaces with high ceilings or spaces with ornamental ceilings and upper wall surfaces. These systems can be combined with other types of detection and suppression systems.
Detection Advantages
In historic structures, early detection is critical to avoid extensive damage or destruction of a significant building and its contents, in addition to the life safety concerns. Fire must be detected early in the smoldering, incipient stage before active flaming occurs. Once flames have occurred it is too late, serious damage will occur from the flames and then from the water used to extinguish the fire.
Fires have four stages: incipient, visible smoke, flame, and heat. Smoke at the incipient stage of a fire is low in density, below the detection level of conventional smoke detectors. Also, early smoke does not always rise to reach ceiling-mounted detectors, especially in large open spaces with high ceilings.
Air sampling (aspirating) fire detection systems offer greater sensitivity and speed than conventional detectors. Location of the air sampling tubes is not limited to the ceiling. The exposed tubes are small, easy to conceal, and can be located below the ceiling level to pick up smoke earlier, before it rises. The systems can detect invisible particles generated during the pre-combustion stage of a fire, at levels of obscuration as low as 0.003% per foot, as compared to 3% per foot sensitivity of a typical spot-type photoelectric smoke detector. Manufacturers' literature claims they are up to 1000 times more sensitive than conventional ionization or photoelectric type smoke detectors. This early warning capacity makes it a particularly attractive alternative for historic structures and large open areas such as atriums, open stairs, and two story spaces.
Aesthetic Advantages
Conventional photoelectric and ionization fire detectors (point detectors) are designed to detect fire at a specific location, requiring a number of properly placed smoke detectors to cover a large area. These units are fairly large and are difficult to conceal. Decorative interiors, especially ceilings, in historically significant buildings make it difficult to install traditional smoke detectors without taking away from the historic character and materials of the space.
Air sampling detection systems offer less obtrusive installation with minimal disturbance and damage to architectural and historic features and spaces. Components are small, easy to conceal, can be placed in a wide variety of areas, and provide wide coverage. The only elements visible in a space are the tiny, clear plastic sampling tubes which can be concealed in light fixtures, ledges, and ornamental ceilings, allowing wider dispersal of the detection system with minimal architectural impact. The piping is flexible and can fit in almost any space. The actual detector can be located in a different room. A single detector is designed to monitor up to 20,000 square feet. It would take 20 point detectors to cover the same area.
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