Replacing LI-720 Scrub Packs

The scrub packs used in the LI-720 should be replaced yearly. Replacement scrub pack kits are available as part number 99512-080. Contact LI-COR or your sales representative for replacement scrub packs.

  • Both the upper and lower housings have scrub packs. Always replace both of them at the same time.

    One scrub pack is in each housing.

  • Do not open the packs until you are ready to install them. Install the replacement scrub packs promptly after receiving them.

  • Complete the procedure in dry ambient air, such as a room or vehicle cab with the air conditioning on. The scrub packs may become depleted if exposed to humid air prior to installation.

Part Number Description
99512-080 Scrub Pack Kit
99512-058 Scrubber Assembly (2)
98512-092 Custom Washer (2)
150-14386 Machine Screw; M2 x 6 mm (12)

Warning: Scrub packs enclose small quantities of Ascarite™ II and magnesium perchlorate. These chemicals may be hazardous. Wear goggles and skin protection (e.g., latex gloves). Do not breath dust or allow the chemicals to come into contact with your skin. Check local regulations before discarding the scrub packs. For SDS, go to licor.com/support and search for SDS.

To replace the scrub packs:

  1. Power off the sensor, remove it from the tower, and set it on a workbench.

    Handle the instrument carefully and avoid impacts.

  2. Remove the four screws (PH1 Phillips driver) and washers that secure upper the scrub pack.

    The old screws and washers can be discarded. Be sure to dispose of the packs safely and in accordance with local laws.

  3. Pull the scrub pack straight up.

    Use a small flat screwdriver to dislodge it, and be sure the O-ring comes out with the scrub pack.

    use a screwdriver to remvoe the cap.

  4. Open the new scrub pack only when you are ready to install it.

    Do not open scrub packs early, as doing so will reduce the scrubbing efficacy. Install them immediately after opening the package.

  5. Be sure the O-ring is in place, and then press the new scrub pack into place.

    The flat side should be toward the bottom of the sensor.

  6. Insert each screw into the ring washer and tighten until hand-tight.

    The kit includes four extra screws.

  7. Repeat this with the scrub pack in the lower housing.

After replacement, it will take some time to scrub the volumes of CO2 and water vapor. At an RH_src >4% for 10% of samples in a 30-minute reporting period, the LI-720 will report an issue in the diagnostics for that 30-minute flux result. Allow at least 24 hours for the scrub packs to remove CO2 and moisture from the housings. Diagnostics related to RH_src should clear after several hours or days.