Gemini 501-B User Manual
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Contents
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63.2.8. Blower, Hose, Wands, Diffuser, and ShroudBlower. The blower provides air to dilute the aerosol from the nebulizer. The dilution-air adjust knobcontrols the flow rate of the dilution air (See 3.2.7).Hose and wand. Insert the plastic end of the 5-ft., 1-1/2 inch diameter flexible hose to the outputport (right side) of the analyzer and connect the other end to the wand and the shroud. Anoperator using a single-length wand can reach a normal ceiling height of about 8 feet.Additional wands may be coupled to reach ceilings as high as 20 feet. For a 30-feetapplication, an optional high-reach kit is also available. It is a retractable pole that allowsyou to reach up to 30-feet ceiling.Wall-mounted detectors testing adaptor Connect one end of the adaptor to the wand and the otherend to the diffuser and the shroud. The adaptor can be bent at any arbitrary angle up to 90degree. This facilitates the testing of wall-mounted smoke detectors.Shroud. The purpose of the shroud (the clear plastic bowl) is to cover the detector so that theaerosol of known concentration is not affected by room air. For good results the edge of theshroud should touch most of the wall surface around the detector.However, since the test stream is flowing out at a high rate of about 2.1 ft3/min (60 L/min),room air would not be able to dilute the smoke stream even though the shroud is as muchas 1/2 inch away from the wall. For some older models of smoke detectors and ductdetectors, a different size of shroud may be needed. Please contact Gemini Scientific formore info.Diffuser. The diffuser inside the shroud has six holes, which limits the flow rate and distribute thesmoke evenly to the detector. It also serves as a connection between the wands and theshroud. Holes on the diffuser may need to be closed or enlarged to attain correct flow rate.(See 3.2.7)Duct detector testing adaptor This optional testing adaptor allows you to test duct detectors.3.2.9 TemperatureTo monitor the aerosol temperature, the temperature probe should be inserted into the smallaluminum well on top of the nebulizer. Temperature reading is shown at the lower left corner of theLCD. The sensitivity reading on the LCD is corrected for fluctuations in temperature. However,operating temperature should not be below 70o F when smoke output is greatly reduced due to thelow temperature. Temperature above 90 degree during testing would be fine since the sensitivity isadjusted accordingly.3.2.10 Exposure TimeThe purpose of the timer is to help the inspector control the smoke exposure time. If the detectordoes not respond within 30 to 45 seconds after exposure, stop the test. Reset to a higherconcentration level for the next test. However, for some brands of detectors (with a longer samplingtime), or in borderline cases, 45 to 55 seconds or more of exposure time may be required to find themaximum sensitivity.How fast the detector responds should not be used to determine the sensitivity of the detector. Toavoid nuisance alarm, some detectors are designed to alarm only after exposure to smoke for atleast 24 seconds at the proper designated level of concentration. Please refer to the smoke detectormanufacturer’s specifications and manual for more details. |
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