# Calibration of Aranet CO₂ and Temperature Sensor The sensor comes factory calibrated, but when recalibration is needed, it can be done in the following steps: 1. Screw out the top part of the sensor. 2. The small dipswitch on the PCB board should be set in the **MAN** position 3. Press and hold **CALIBR.** button till the red LED starts to blink; 4. Now, sensor should be left in the fresh air outdoor environment during the calibration process for 30 minutes without any person nearby. 5. When the calibration process is finished, screw the sensor's top part back. A brief video of the process can be found [**here**](https://assets.aranet.com/documents/CO2_T_sensor_calibration.mp4). The general recommendation is to redo the calibration for Aranet CO₂ sensors once per year, as sensor measurement values will start to drift over time. Out-of-the-box brand new sensors have the factory calibration, and for some time, there is no need to do it and measurements will be precise just by putting the batteries and pairing sensors to the Aranet Pro base station. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://help.aranet.com/pro-series-sensors/pro-series-sensors/calibration-of-aranet-co-and-temperature-sensor.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.