One size fire and life safety system does not fit all. Some products are more appropriate than others in certain situations, environmental conditions, occupancy and structure, among other considerations. It is imperative that fire protection engineers and systems integrators do research and that the Authority Having Jurisdiction (AHJ) is consulted for code applicability before selection.
Half the battle is knowing which fire detection options are available, as noted below, as well as how to best apply and adapt these to the building environment.
Conventional detectors specialize in the detection of slow, smoldering fires and are often ideally suited to general commercial and multi-family residential applications. These are a practical choice for typical applications when they don’t require an intelligent device and the primary objective is to protect lives from fire and smoke.
Most smoke detectors work either by photoelectric or by ionization, while others use both detection methods to increase sensitivity to smoke. These detectors have an approximate maximum coverage area of 900 square feet.
Ionization smoke detectors are inherently adept at detecting flaming fires and 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 and are prone to nuisance alarms.
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 more critical settings.
Intelligent smoke detectors
Some of today’s fire systems are “smart” or “intelligent.” The components of these systems are able to engage in two-way dialog, analyze complex environments, adjust their own sensitivity levels and make educated decisions based on stored data.
Intelligent, high-sensitivity spot detectors typically use 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 percent per-foot obscuration. Such early detection provides valuable time for personnel to investigate the affected area and take appropriate action to mitigate risk.
One important benefit of intelligent, addressable smoke detectors is that they enable the panel to quickly pinpoint locations of detectors in alarm. They can also identify detectors that have been tampered with or require maintenance. Some intelligent detectors can automatically compensate for changes in the environment, such as humidity and dirt buildup, and can be programmed to be more sensitive during certain times of the day.
Aspiration smoke detectors draw air into a high-sensitivity sensor through a pipe network to provide Very Early Warning Fire Detection. This approach enables these detectors to protect mission-critical facilities and high-value assets from the faintest traces of smoke.
The newest aspiration detection systems provide enhanced nuisance immunity along with the capability to provide Very Early Warning Fire Detection. Also look for programmable alarm levels and pre-alert particulate levels that can be set to specific site requirements. Integral Ethernet connectivity and email notification of device status updates enable facility managers to respond appropriately to any situation.
Because it can be installed remotely while sampling points can be run into the protected area through the pipe network, an aspiration unit can be an ideal choice for challenging environments, such as cold storage facilities or medical testing rooms. The pipe network can also be hidden above a ceiling or in a floor cavity to eliminate tampering in public areas or to maintain a facility’s aesthetics while protecting important assets, such as in a museum. Aspiration systems are also ideal to protect mission-critical environments, such as telecom/data centers and hi-tech fabrication facilities.
Beam smoke detectors
Most beam smoke detectors are designed to save time and money and provide better detection capabilities for many open-area and high-ceiling applications. Many of these detectors provide a very wide coverage area—up to 19,800 square feet. They are well suited for applications where it is difficult to install or maintain traditional spot detectors or where smoke might not reach the ceiling due to stratification.
Some beam detectors may include a small reflector that is mounted opposite the transmitter/sensor, so only one device needs to be wired. They have a wider operating temperature range than typical spot detectors and work well in colder environments, such as cold storage warehouses and sports arenas, as well as other high-ceilinged areas such as atria, lobbies, gymnasiums and factories.
A duct smoke detector is a device or group of devices used to detect the presence of smoke in the airstream of ductwork sections of the HVAC air-handling systems used in industrial/commercial facilities. Duct smoke detection assists in preventing the spread of toxic smoke and combustion gases and also can be used to assist in equipment protection applications.
Made to operate in air velocities from 100 to 4,000 feet per minute, some photoelectric duct smoke detectors utilize a pivoting housing that fits both square and rectangular footprints on round or rectangular ductwork. These detectors provide the superior false alarm immunity necessary to reduce callbacks in duct applications prone to nuisance conditions. There are duct detectors that use sampling tubes that plug into these often difficult-to-access detectors from the front or back of the device without the need for tools.
For challenging or unique duct smoke applications, high-sensitivity duct smoke detectors use a laser sensor to provide very early warning of fires to protect high-value assets and mission-critical operations from fire and the spread of damaging smoke through air management systems.
NEMA 4-rated watertight duct smoke detectors are built to operate on rooftops or other areas that are exposed to water or the weather without the need for bulky or costly enclosures. Many of these detectors can operate in airflow speeds from 100 to 4,000 feet per minute, temperatures from –4°F to 158°F and humidity ranges from 0 to 95 percent (non-condensing). The watertight, UV-resistant housing provides protection against rain, windblown dust and dirt, splashing and hose-directed water.
Multi-criteria fire detectors
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.
Intelligent multi-criteria detectors monitor more than one product of a fire in order to achieve higher levels of sensitivity, detect a wider range of fires or improve accuracy. There are a variety of multi-criteria fire detectors, some combining up to four sensing technologies – smoke, CO, heat and infrared – with intelligent detection algorithms that enable the detector to respond very quickly to an actual fire while maintaining the highest levels of nuisance immunity available.
This type of detector is ideal for challenging applications where typical spot detection may initiate nuisance alarms. Places where nuisance alarms would be costly or dangerous, such as theaters, medical facilities, dormitories, senior living centers, financial trading centers, telecommunications networks and manufacturing facilities, could especially benefit from this type of detection.
Another intelligent multi-criteria detector combines photoelectric and thermal sensor signals to provide early and accurate fire detection. Some may automatically adjust sensitivity within specified parameters, further enhancing response speed and accuracy. Then there are multi-criteria detectors that combine smoke detection and CO detection in one unit. For fire, the detector enables enhanced sensitivity to real fire with heightened immunity to nuisance particulate. For CO, the detector’s electrochemical sensing cell creates a separate signal for life safety CO detection.
Heat detectors
Heat detectors provide property protection against fire and for non-life-safety installations where smoke detectors are inappropriate. Heat detectors are suited for areas with unsuitable conditions for smoke detectors, including places that experience rapid changes in temperature or where high ambient temperatures exist, such as storage facilities, garages, mechanical rooms, commercial kitchens and other service areas.
