7 Aspirated Smoke Detection Why use ASD?Early warning – achieved thru increased sensitivity and active air samplingDifficult to detect smokeStable performance in adverse environmentsAccess is difficult
8 Aspirated Smoke Detection Early WarningWidest sensitivity range availablecan achieve %obs/ft values a 1000 times greater than conventional photo-electricActive vs. Passiveair sampling can capture smokeCollective samplinggives the advantage of pulling together quantities of smoke from many sampling holes. Collectively early warning notification can be achieved.
9 Aspirated Smoke Detection Early Warning ApplicationsTelecommunicationsIT / Data CentresSemi-conductor FabHigh Value Storage – museums, galleries, libraries, archive.
10 Aspirated Smoke Detection Telecom & Data CentreHigh valued equipmentEmergency servicesCritical data storageDown-time causes loss of revenueEarly warning reduces the risk from fire
11 Aspirated Smoke Detection NFPA 758.2* Automatic Detection Systems.Automatic detection equipment shall be installed to provide early warning of fire. The equipment used shall be a listed smoke detection–type system and shall be installed and maintained in accordance with NFPA 72®, National Fire Alarm Code®.8.2.1* Automatic detection systems shall be installed in the following locations:(1) At the ceiling level throughout the information technology equipment area(2) Below the raised floor of the information technology equipment area containing cables(3) Above the suspended ceiling and below the raised floor in the information technology equipment area where these spaces are used to recirculate air to other parts of the buildingWhere interlock and shutdown devices are provided, the electrical power to the interlocks and shutdown devices shall be supervised by the fire alarm control panel.The alarms and trouble signals of automatic detection or extinguishing systems shall be arranged to annunciate at a constantly attended location.A.8.2 Fire detection and extinguishing systems should be selected after a complete evaluation of the exposures. The amount of protection provided should be related to the building construction and contents, equipment construction, business interruption, exposure, and security need. For amplification of the important need of fire protection, see Chapter 4.A The detection system selection process should evaluate the ambient environmental conditions in determining the appropriate device, location, and sensitivity. In high airflow environments, air-sampling detection devices should be considered.
12 Aspirated Smoke Detection NFPA 76General. Facilities containing greater than 232 m2 (2500 ft2) of signal-processing equipment area shall be provided with a very early warning fire detection (VEWFD) system for detection and alarm processing in accordance with Chapter 8.* Use of VEWFD systems with an alert (pre-alarm) condition shall provide for an initial response by authorized personnel prior to fire department notification.VEWFD Sensor and Port Installation.* Every type of sensor and port installed in an area shall be limited to a maximum coverage area of 18.6 m2 (200 ft2).* Where two levels (high and low) of ports or sensors are provided, each level shall be limited to a coverage of 37.2 m2 (400 ft2) or less per port or sensor.(A) The coverage limitation between high and low levels shall be limited to 18.6 m2 (200 ft2) or less providing for staggered port or sensor arrangements between each level.* Sensors or ports shall be installed to monitor return air from the space.(A) Where stand-alone packaged HVAC units are installed, sensors or ports shall be installed where return air is brought back to the unit.(B) Sensors or ports shall be installed such that each covers no greater than 0.4 m2 (4 ft2) of the return air opening.Maximum transport time from the most remote port to the detection unit of an air- sampling system shall not exceed 60 seconds.
13 Aspirated Smoke Detection Consequences of an incipient fire“95% of all fire damage within facilities housing electronic equipment is non-thermal”* US Federal Commission of Communications
14 Aspirated Smoke Detection Large amounts of plastics in cabling, circuit boards, etc.Smoldering fire releases harmful corrosive by- products (HF, HBr, ZCl).Can lead to immediate orunexpectedfailure.
15 Aspirated Smoke Detection Difficult to Detect SmokeLarge open spacesDilutionHigh air change rates and distribute and dilute smokeBackground smokeAdjusting for high ambient “non-fire” related smoke
16 Aspirated Smoke Detection Difficult to Detect Smoke ApplicationsAtriumsPower generation facilitiesData CentreWater, waste and sewage treatment facilitiesIndustrial – mining, steel mills, petro- chemical, wood, pulp and paper
18 Aspirated Smoke Detection AtriumsStratificationThermal liftDilution in large volumeSmoke movement by mechanical ventilation
19 Aspirated Smoke Detection AtriumsSampling at multiple points
20 Aspirated Smoke Detection High equipment heat output + High cooling demand = High air change rates
21 Aspirated Smoke Detection Air Change Rate CalculationAir change rate needs to be calculated for all protected areas (i.e. under-floor, room, above ceiling)Determine volume of all protected spacesSum total CFM for the HVAC system serving the space + fresh airAir Change/Hour = Total CFM x 60minVolume
22 Aspirated Smoke Detection Smoke Detector Spacing Based on Air MovementMin/Changes Changes per Hour m2 spacing ft2 spacing
23 Aspirated Smoke Detection Access is DifficultRemote testingDetector and test point can be remotely located to facilitate maintenanceFewer test points
24 Aspirated Smoke Detection Applications Where Access is DifficultAtriumsEnergized spacesPrison CellsConfined spaces (crawl, attic)Hazardous areasElevator shaftsCongested ceilings
25 Air-Sampling Detection Overview Annual inspection is performed at most remote sampling hole on each pipeLast Hole (Test Point)Air-Sampling Detector(Test Point)Record transport time and compare
26 Aspirated Smoke Detection AtriumsTesting done at most remote point
27 Aspirated Smoke Detection Prison CellsSampling is performed in exhaust duct of cell.Testing can be done remotely
28 Aspirated Smoke Detection Prison CellsSampling point concealed behind return air grillOut of site out of mind
29 Aspirated Smoke Detection Correctional sampling point alerts when blocked