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

authors

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

keywords

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

document type

abstract

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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