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Table 2 Expected indoor (Oslo University Aula) to outdoor (Oslo central urban background) concentration ratios and pollutant dry deposition velocities

From: Estimation of the historical dry deposition of air pollution indoors to the monumental paintings by Edvard Munch in the University Aula, in Oslo, Norway

Pollutant Indoor/outdoor concentration ratioa Indoor dry deposition velocity (cm s−1)
SO2 0.23b 0.057g
NO2 0.9c 0.004h
O3 0.5d 0.021i–0.077g
PM2.5 before 1975 0.5–0.8e 0.02j
PM2.5 after 1975 (with mechanical ventilation filtration) 0.1–0.4f 0.02j
  1. aSee also Additional file 1
  2. bMeasured in the National Gallery of Oslo.
  3. cSuggested probable value based on data from the National Gallery and the literature, allowing a slight reduction to the indoors.
  4. dMeasured in the Aula in the winter 2019.
  5. eBased on [60] and the assumption that there will probably have been some reduction to the indoors.
  6. fBased on evaluations of possible variations in the PM2.5 I/O ratio from the measured average ion I/O ratio in the Aula (Table 1) and the considerable general uncertainty.
  7. gAverage of surface dry deposition velocity to paintings at RH = 30% and RH = 50% [56].
  8. hA two times higher value (0.008 cm s−1) was reported from measurements [56] at RH = 30% than from RH = 50–90% (0.004 cm s−1) The value of 0.008 cm s−1 seems anomalous and it was decided to use the value of 0.004 cm s−1, for the situation with RH = 40% in the Oslo University Aula.
  9. iObtained by modelling to measurements by [57, 58] report a typical value of 0.051 cm s−1 “based on studies by [61] and by [62]”
  10. jAverage experimental dry deposition velocity to the indoor building surfaces of the historic house museum of Apsley House in London [60]. Simulation of the mechanically ventilated room in the house (Waterloo Gallery) showed the same value [63]