VOC calibration

Our community has several monitors all in the same direction relative to an emitting source. The VOC readings are extremely high - higher than the monitors are programmed to read. We were told that the calibration is not functioning correctly. The three monitors, however, all have the same pattern of readings. Are the monitors actually measuring VOCs or are they measuring other things like humidity…? If they are measuring VOCs is there an algorithm or something that we can apply to the readings to correct them?