Patent ID: 11933508
Assignee: MEASURED AIR PERFORMANCE, LLC
Field: Measurement (Instruments)
Classification: CPC F  G  Y | IPC F  G

Claim 13:
14. A method of performing exhaust demand control using a system for measuring one or more contaminants at one or more exhaust locations within one or more exhaust ducts or plenums served by an exhaust fan system having one or more exhaust fans generating a negative pressure, comprising:
measuring the one or more contaminants within the one or more exhaust locations using a multipoint air sampling system having one or more sensors and two flow rate control elements which include a high flow rate element to provide a purge flow rate and a low flow rate element to provide a sensing flow rate;
comparing contaminant concentration measurements from the one or more exhaust locations against an action level to create a fan setback signal which controls a setback state of the exhaust fan system;
preventing an exhaust fan system instability by controlling the operation of the one or more exhaust fans according to a sequence delay provided by a control logic of a control system where the sequence delay is enabled when the contaminant concentration measurements from the one or more exhaust locations exceeds the action level, wherein the sequence delay in part determines a minimum time that the fan setback signal is disabled; and
ensuring sensor accuracy and reliability by implementing a sensor protective mode for a period of time designated by the sequence delay, the sensor protective mode enabled when the contaminant concentration measurements from the one or more exhaust locations exceeds the action level;
the sensor protective mode comprising the combined steps of:
discontinuing the air sampling process performed by the multipoint air sampling system,
isolating the one or more sensors from the contaminant source, and
enabling a tubing flushing function which uses the negative pressure of the one or more exhaust locations to draw ambient air through each tube which connects between the multipoint air sampling system and the one or more exhaust locations via a flow path to ambient that is enabled within the multipoint air sampling system when sensor protective mode is enabled.