This tube is used to purify ambient air to form a zero standard for calibrating both CO2 & VOC sensors in ambient background. Calibration should be performed at the same temperature, humidity and flow as the measurement. To connect to an instrument, use Inlet Tube Adapter p/n 025-3002-000 according to the instructions on the reverse side. See Technical Notes 172 and 178 for more details on use and how to connect other monitors. This tube contains the same VOC zeroing layer as tube 025-2000- 010 with an additional CO2 absorbing layer. Used with IAQ RAE and MultiRAE IR Monitors.