Using the LI-7810 CO2 Zero Kit

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The LI-7810 CO2 Zero Kit (part number 7800-950) is used to adjust the CO2 zero reading. It is best to adjust the zero with a tank of calibration gas that is free of volatile organic compounds (VOCs), but the zero kit can be used if tank gas is unavailable. Adjusting the zero will improve the accuracy of CO2 measurements in situations where an absolute concentration is needed. The kit includes two chemical columns—one for Sorbead® Orange CHAMELEON® (desiccant) and one for Soda Lime (CO2 scrubber)—and sections of tubing to connect the kit to the analyzer air inlet.

Part Number Description
222-01824 Bev-a-line Tubing
300-05375 ¼” Ferrule Set
300-05896 ¼” Compression Fitting
300-07124 Quick Connect Plug
622-16951 Silica Gel Desiccant Sorbead Orange Chameleon
9964-090 Wet Soda Lime
9968-258 Chemical columns (2)

When setting the CO2 zero, the LI-7810 will draw air through the columns, purging it of H2O and CO2, and then into the analyzer. The instrument needs to warm up with ambient air (not scrubbed air), so power it on and let it warm up while you prepare the zero kit.

The CO2 zero function is supported by software version 2.0.17 and newer. Software updates are available from licor.com/env/support/LI-7810/software.html.

Assembling the Zero Kit

Power on the instrument and let it warm up while you prepare the zero kit.

  1. Fill one tube with Soda Lime.
  2. Remove one end cap and filter. Fill the tube completely and then press the end cap back in place. Be sure the filter is inside the cap.
  3. Fill one tube with the desiccant.
  4. Again, be sure the filter is inside the cap when you install it.
  5. Connect the tubes in line.
  6. Air must be drawn through the Soda Lime CO2 scrubber before it is drawn through the desiccant!
  7. Connect the columns to the air inlet with the remaining piece of Bev-a-line tubing.
  8. Tighten the compression fitting on the inlet.

Checking the Zero

Be sure that the instrument is warmed up before connecting the zero kit to the inlet.

  1. With the instrument warmed up and the zero kit connected to the air inlet, allow the readings to stabilize.
  2. Observe the CO2 reading. It should approach zero — it may take up to 25 minutes.
  4. Click on the CO2 value to display a detailed view and statistics of the measurement.
  5. Here you can see the slope and standard deviation. You prefer a slope very near zero, which indicates that the air being measured is completely purged of CO2. You can adjust the Graph Range (Seconds) to recompute the slope based on shorter or longer period of time. A slope near zero will be within the performance specifications of the instrument.
  7. Zero the CO2 measurement.
  8. Under Settings > Advanced, click CO2 Zero.
  10. The instrument will apply the new setting. It may take a few minutes. After it is done, observe the measurements for a moment to be sure you’re satisfied with the zero adjustment.

Storing the zero kit

When the zero kit is removed, the chemicals in the columns will be exposed to ambient air. If you want to use them again, store them in a glass jar.

Sorbead® can be regenerated after it becomes saturated—it will lose the orange color when it is saturated. To regenerate Sorbead, spread the beads into a single layer in a shallow tray. Place it into a 120 °C drying oven for 1 to 2 hours. Place the hot beads into a glass jar and tighten the lid. Let it cool. Store the regenerated Sorbead in a glass jar (avoid plastic). If you don’t want to save the scrubbing chemicals, dispose of them in municipal waste.