Measurements and Modelling of OH and Peroxy Radicals in an Indoor Environment Under Different Light Conditions and VOC Levels


  • Fiorentino Eve-Agnès
  • Chen Hui
  • Gandolfo Adrien
  • Lannuque Victor
  • Sartelet Karine
  • Wortham Henri


  • Indoor air
  • Radical chemistry
  • Photolysis
  • Air mixing
  • Light distribution
  • VOCs

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Indoor measurements of OH and sum of peroxy radicals XO2=HO2+RO2 were conducted in a room using window glasses of different transparencies and applying different coatings to the walls. Average OH and XO2 concentrations were found to vary in the range (0.6-4) × 105 molecule cm-3 and (1-7) × 107 molecule cm-3 respectively with anti-UV windows, and (6-10) × 105 molecule cm-3 and (4-16) × 107 molecule cm-3 respectively with borosilicate glasses. The OH and XO2 concentrations were compared with simulation results obtained using the H2I model, which accounts for the mixing between the sunlit and shaded volumes of the room. Taking into account the measurement uncertainty, the simulated OH concentrations agree with the observations on average while the simulated XO2 concentrations tend to be overestimated. Based on the model results, ozonolysis of unsaturated VOCs and photolysis of HONO and of organic compounds are found to represent the main primary sources of OH and XO2 radicals, the latter being more important in the sunlit volume. Despite the lower rate of the radical initiation in the shaded volume, the difference of radical concentrations in the shaded and sunlit volumes is mitigated by an interplay between the mixing time and the lifetime of XO2 radicals, allowing efficient transport of XO2 radicals into the shaded volume and acting there as a source of OH via radical propagation processes.

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