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Why is the nitrogen dioxide (NO₂) level so high?

The most probable cause for a high reading is the presence of Nitrogen dioxide (NO₂) in the air.

The nitrogen dioxide (NO₂) sensor installed in the air-Q measures based on an electrochemical measuring principle. An abrupt change in temperature or humidity, e.g. by opening a window, can affect the sensor and lead to a positive or negative peak in the sensor values. Such peaks disappear after a few minutes and do not require any action by the user.

However, various effects, e.g. climatic shocks, can also cause a shift of the zero line. The air-Q can normally correct faulty values automatically within a few days (automatic calibration). A prerequisite for this, however, is that the air-Q is in a dynamic / clean environment, i.e. is regularly ventilated. One indicator used here is the VOC value, which must frequently fall below 700 ppb. If the necessary conditions cannot be achieved or can only be achieved infrequently, the automatic calibration does not work well or fast enough. In this case, manual calibration can be helpful.

See here: How do I perform a manual calibration?

Another reason for very high or abnormal readings at certain points can be the cross-sensitivity of the nitrogen dioxide sensor. For example, it reacts slightly positively to ozone (O₃) and chlorine (Cl).

All general conditions must therefore be checked and the measured values must also be brought into connection with the measured value of the ozone (O₃) sensor in the air-Q in order to exclude possible cross-sensitivities as a cause.

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