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RequirementsforaVentilationsystem
AVentilationsystemsuppliesfreshairintoaroomandexhauststhecontaminated
air.Letuslookatthefollowingsamplesystem:
• Aroomcontainsanextractorfanandafresh-airfan.
• Eachfanismonitoredbymeansofaflowsensor.
• Thepressureintheroommayriseabovetheatmosphericpressure.
• Thefresh-airfanmayonlybeswitchedoniftheflowsensorsignalsthesafe
operationalstateoftheextractorfan.
• Awarninglampindicatesfailureofoneofthefans.
7.3.1Standardsolution
ThecontrolcircuitdiagramofVentilationsystemformerlyasfollows:
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