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Case Study: Air Pressure Monitoring for a Chemical Fume Hood

Fri, 06/15/2012 - 11:21am

A pressure and temperature data logging system is providing wireless monitoring of a chemical fume hood used in a laboratory to contain and then expel vapors, dust, gases, and fumes as air flows into the hood from the front side of the cabinet and then out via the ducted hood exhaust system.

The fume hood, designed for two operators, has a Fiberglass reinforced polyester liner and shields workers with a sash that contains harmful aerosols. A scrubber absorbs fumes through a chamber, which is then saturated with water. The chemicals are washed into a sump and the fumes dispersed into the atmosphere.

To monitor the laboratory's pressure differential, which had to be negative to the space outside the room, the facility owner investigated a wireless data logging solution. The system needed 4 to 20 mA inputs to connect with commercial pressure transducers and an ambient temperature sensor. An alarm was needed to contact staff whenever the differential pressure changed so that equipment could be serviced or replaced.

The facility installed two Accsense A1-01a wireless environmental data logger pods from CAS Dataloggers, Chesterland, Ohio. One was installed in the chemical fume hood's control panel and another in the room immediately outside the laboratory door. An Accsense B1-06 wireless data logger gateway featuring built-in 10/100BaseT Ethernet enabled online connection with the pods' data. Both wireless pods were then connected to pressure transducers to record the differential pressure.

The environmental sensor pods monitored the pressure in both rooms using external 4 to 20 mA and 0 to 5 V inputs. The laboratory's pod recorded ambient temperature using an internal temperature sensor. All data was sent to the Internet. The data loggers could operate on either battery or AC power. A 250-sample data buffer allowed the pods to compensate in the event of a power or Internet outage.

Using the wireless gateway, the pods continually monitored the fume hood’s pressure and temperature data, giving management remote access to data in real time. The gateway could send all the data to a secure cloud server or as a local ASCII stream, which could be incorporated into custom software. Once online, data could be downloaded as a .csv file and loaded into a database application.

Advanced alarms monitored the incoming data and sent email, pager, or phone warnings to multiple addresses whenever an alarm was triggered. The company's online Accsense account gave instant access to charts showing all measurement history with ranges as narrow as five minutes or as wide as 90 days.

CAS Dataloggers, www.DataLoggerInc.com

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