The most likely cause of a high reading, is the presence of Ozone (O₃) in the air.
The Ozone (O₃) sensor in the air-Q measures according to an electrochemical measuring principle. It can come here by various effects e.g. climatic shocks to a shift of the zero line. This can be remedied by calibration.See here: How do I perform a manual calibration?.
Another cause for selectively very high or deviating measured values can also be the cross-sensitivities, which the ozone sensor has. For example, it reacts positively to Nitrogen dioxide (NO₂), Ethanol (C₂H₅OH) and Chlorine (Cl) and negatively from Hydrogen sulfide (H₂S).
Thus, all general conditions must be checked and the measured values must also be brought into connection with the measured value of the ozone (O₃) sensor and the nitrogen dioxide (NO₂) sensor as well as the VOC sensor in the air-Q in order to exclude possible cross-sensitivities as a cause.