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Photolysis driven indoor air chemistry following cleaning of hospital wards
Photolysis driven indoor air chemistry following cleaning of hospital wards
****!!!!***** (2020) {This study was done via computer modeling that predicted some significantly different results than real-world. Example: Degradation of ClO2 throughout room was based on rate 1 m from fluorescent lamp. In actuality, little UV reaches beyond a couple meters, so rest of gas in room is unaffected other than gas blown into close proximity.} {Negative byproducts from chlorine dioxide gas fumigation} "previously unconsidered potential consequence of such cleaning technologies: the photochemical formation of high concentrations of hydroxyl radicals (OH), hydroperoxy radicals (HO2), organic peroxy radicals (RO2), and chlorine radicals (Cl) which can form harmful reaction products when exposed to chemicals commonly found in indoor air." "Steady-state Cl concentrations are elevated at all OClO concentrations under bare fluorescent and attenuated outdoor lighting, with little dependence on OClO concentration... because species involved in the reactions that lead to Cl formation, as well as Cl itself, can undergo competing reactions" " Sunlight is attenuated as it passes through windows, such that 3 and 10%, respectively, of UV and visible light ingresses" "We assume a ward volume of 35 m3 with an area to volume ratio of 1 m2/m" " temperature was assumed to be 293 K and 50% relative humidity" "The emissions were set to provide the approximate concentrations reported in the literature for NTD use... 3000 and 350 ppm for OClO (to reflect two commonly used concentrations). This required emission rates of... 0.8 and 0.1 ppm/s to deliver 3000 and 350 ppm of OClO " "The emissions were assumed to last for one hour and then stop. After another hour (at noon), ventilation was resumed at 2 per h. There is very little information in the literature on how long the gases will be emitted during cleaning" "Maximum... concentrations occurred [of] RO2 and Cl with OClO [chlorine dioxide] photolysis. Elevated concentrations may persist for hours... Products from reactions involving radicals could significantly decrease air quality when disinfectants are used, leading to adverse health effects for occupants" "OClO photolysis under attenuated sunlight is ~20 times faster than under bare fluorescent lighting," "O3 levels generated from OClO photolysis are much higher than those commonly attained using O3 as the primary fumigant""Photon fluxes will vary greatly throughout a room" "we suggest that the efficacy of NTDs on reducing loadings of several strains of bacteria should be further studied in the dark and under illumination from different indoor lighting. It is possible that efficacy will be greatly enhanced under common lighting sources such as fluorescent lights due to the production of radicals that may inactivate bacteria more effectively than the disinfection agents." "[This info needs verification:] There is no ClOO absorbance at wavelengths longer than 280 nm"
·core.ac.uk·
Photolysis driven indoor air chemistry following cleaning of hospital wards