Since its development, the Early Warning dosimeter forOrganic materials (EWO dosimeter) has been used as botha research and general measurement tool for the evaluationof indoor air quality for preser vation of cultural heritageartefacts. The EWO dosimeter measures the integrateddegradation impact of the environment, comparable to thatobserved on organic materials due to the synergisticeffects of gases (NO2 and O3) and climate (temperature /RH, UV-light).Measurements of impacts of air pollution on EWO dosimeterswere performed in different cultural heritage locationsas part of EU projects, other types of international projectsand as a service to individual institutions. In this study, theindoor air quality in different microenvironments or locationsis assessed based on the results obtained by EWOdosimetry. Correlation between the type of location and thedosimeter results has been obser ved. Indoor locations inhighly polluted cities showed higher dosimeter responsethan more rural locations probably due to more infiltrationof outdoor generated pollutants such as NO2 and O3. In contrast,measurements performed inside enclosures (e.g.showcases / microclimate frames) showed low response ofthe dosimeter and hence low photo-oxidizing effects.