ChemDAQ Steri-Trac, Operation Manual

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For those sensors that have chemical filters (for example the ethylene oxide sensors uses ChemDAQ’s
patent pending Spot-On™ chemical filter to prevent false alarms from alcohols and carbon monoxide),
these filters are consumable and so are usually replaced at the same time that the sensor is calibrated. In
addition, the module has other components that age such as the rechargeable batteries. These
components will also be evaluated during each calibration cycle to ensure that the sensor modules give
the best possible performance.
Is Calibration Difficult?
No - ChemDAQ has a program called the Sensor Exchange Program (SXP), under which ChemDAQ
will periodically send out freshly calibrated sensor modules to end users. ChemDAQ monitors are
designed so that instead of calibrating the monitor on-site, the sensor module is pulled off and a freshly
calibrated and verified sensor module is snapped in. The calibration process can thus be done in a few
seconds and is no more difficult than changing a light bulb. The old sensor module is then returned to
ChemDAQ in the pre-paid shipping box that the fresh module arrived in.
How Often Should I Calibrate My ChemDAQ Monitor?
The sensors used in the Steri-Trac sensor module provide the best performance available for a monitor
of this type. The calibration interval is based on our experience with these sensors; for example
ChemDAQ recommends that ethylene oxide, hydrogen peroxide, and peracetic acid sensor modules be
recalibrated every four months for normal use. If a sensor has been used in a particularly harsh
environment, or has been exposed to very high concentrations of the target gas, or high concentrations of
other gases or vapors then the sensor should be recalibrated. Non-routine calibration can be arranged
through ChemDAQ’s customer service.
Do I have to Track the Calibration Status of All of My Monitors?
No - ChemDAQ tracks when every sensor module is replaced and ChemDAQ personnel contact users
when their sensors are due to be recalibrated. This service eliminates the need for the customer to
develop in-house tracking means.
Why Does ChemDAQ Calibrate the Sensor Modules Instead of Customer On-Site Calibration?
The traditional way of calibrating gas monitors is for the manufacturer to supply portable compressed
gas cylinders, a regulator and tubing to the customer and tell them to calibrate the monitor. On-site
calibration typically involves applying zero air (hydrocarbon free air) to the sensor for several minutes
to record the baseline followed by span gas (test gas with a known concentration of the sensor’s target
gas) again for several minutes.
The calibration process is time consuming and the calibration gases are expensive. In our experience,
most customers dislike the calibration process and are often frustrated especially by the more reactive
gases. The more reactive the gas, the lower the detection limits at which it needs to be detected and so
the lower the concentration that must be used to calibrate the sensor and the more susceptible the
calibration to errors due to adsorption or other loss of target gas.
ChemDAQ’s goal is to make gas detection as simple as possible for the end user and most users much
prefer to simply snap in a fresh sensor module rather than mess with on-site calibration. Furthermore, by
calibrating all the sensor modules in-house, ChemDAQ can ensure that the calibrations are performed