Abstract A number of indoor atmosphere parameters that may affect the preservation of artefacts in two churches in Cyprus, were studied. Temperature, relative humidity (RH), total ultra-violet and total solar radiation, that were continuously recorded during two campaigns (summer and winter), exhibited large diurnal and seasonal variations. Indoor concentrations of nitrogen oxides, determined at the same periods, also exhibited diurnal dependence on air exchange rate (AER) and on their indoor sources from the burning of candles and oil lamps. Indoor concentrations of ozone exhibited dependence on the AER and on the concentration of other indoor pollutants. On a large number of occasions these concentrations exceeded the proposed air quality standards for the preservation of works of art in both churches.