Ammonium nitrate (NH4NO3) and other nitrate salts, as well as ammonium sulfate ((NH4)2SO4), can lead to formation of CO and CO2 on the vaporizer of the Aerodyne aerosol mass spectrometer (AMS) and Aerodyne aerosol chemical speciation monitor (ACSM). This introduces biases in organic aerosol mass and chemical composition measurements, particularly regarding the aerosol oxygen content (f44, O:C). The bias will be small for most ambient data, but can become significant in particular environments (chamber experiments, combustion emissions), for periods of high inorganic mass fractions, and specific ambient research questions (e.g. investigating temporal or spatial different aerosol compositions). Therefore, it needs to be calibrated for in the analyses and interpretation of the data.