Chlorine dioxide has become a widely used disinfectant during the COVID-19 pandemic. Even at very low concentrations, it is a fast-acting broad-spectrum surface

****!!!!****!!!!**** [Might UV light be shined in an area after a fumigation to help decrease the concentration of chlorine dioxide (generally in combination with aeration)? Perhaps even when performing airborne applications of chlorine dioxide at very low levels, a substantial amount of UV light be shined at various intervals to significantly reduce or eliminate existing ClO2 in air to provide confidence that concentration is not being inadvertantly built up beyond desired and safe concentration levels??? ]

****!!!!****!!!! {Abstract} "At extremely low concentrations (about 30 parts per billion), chlorine dioxide (ClO2) gas can inactivate airborne microbes and prevent respiratory disease. It has no toxic effect on animals at this level. However, the temperature dependence of the gas analyzer was found. Therefore, ***data correction is required for each temperature at which gas concentration is measured***. A theoretical analysis of the gas concentrations predicted by the rate of ClO2 gas released from the ClO2 generator was also performed."

****!!!!****!!!!**** (2020). [It seems that light source was solely sunlight through glass window] "The illuminance was adjusted by opening or closing the curtain in the office"

****!!!!**** "We demonstrated here that ClO[2] gas is easily generated by mixing 3.35% sodium chlorite solution (Purogene) and 85% phosphoric acid at a 10:1 volume ratio..." "Under high-humidity (approximately 80% relative humidity), colony formation of both Staphylococcus aureus and Escherichia coli was completely inhibited by ClO2 gas exposure at 1.0 ml/m3 sodium chlorite solution (mean maximal concentration of 3.0 ppm). Exposure at 4.0 ml/m3 sodium chlorite solution (mean maximal concentration of 10.6 ppm) achieved complete inactivation of Bacillus atrophaeus spores. In contrast, without humidification, the efficacy of ClO2 gas was apparently attenuated, suggesting that the atmospheric moisture is indispensable. Delicate electronic devices (computer, camera, etc.) operated normally, even after being subjected to more than 20 times of fumigation."

****!!!!****!!!*** "A single ClO2 application was found to reduce the bacterial and fungal concentration levels by as much as 65% and 30%, respectively. By contrast, a twice-daily ClO2 application was found to reduce the bacterial and fungal concentration levels by as much as 74% and 38%, respectively. The statistical analysis results showed that the residual bacterial concentration level was determined primarily by the number of individuals present in the cafeteria, the temperature, and the ClO2 concentration, whereas the residual fungal concentration level was determined mainly by the temperature, the total number of suspended particles, and the ClO2 concentration."

****!!!!****!!!!*** {Original paper at https://www.jstage.jst.go.jp/article/yakushi/127/4/127_4_773/_pdf} "The efficacy of chlorine dioxide (ClO2) gas at very low concentrations for hyphal growth of Alternaria alternata related to fungal allergy was evaluated... ClO2 gas (average 0.075 ppm, 0.21mg/l) inhibited hyphal growth of the fungus, but not germination of fungal spores. The hyphal length was more than 1780mm under air conditions(control)and 49±17mm unde rClO2 gas conditions for 72 h. According to the international chemical safety card, threshold limit values for ClO2 gas are 0.1 ppm as an 8-h time-weight average and 0.3 ppm as a 15 min short-term exposure limit. From these data, we propose that treatment with ClO2 gas at very low concentrations in space is a useful tool for the growth inhibition of fungi in the fields of food, medicine,etc. without adverse eŠects"

***** {Calculation methods for air concentrations of gas in ppm"the OSHA PEL in mg/m3 is absolutely fixed and not subject to corrections for temperature and pressure." "This constraint implies that volume concentration of gases in parts per million (ppm) must be with reference to some defined temperature and pressure; these are NTP (25 °C and 760 mm Hg) in the OSHA PEL limit."

{***Includes useful illustration of size related to viruses, bacteria, etc} At 124 picometers (0.000124 micrometers), a chlorine dioxide gas molecule is *****much smaller than any microorganism****. Chlorine dioxide is a real gas and by definition expands and conforms to the shape of the area in which it is held and acquires a uniform density inside that area, even in the presence of gravity and also regardless of the amount of equipment in the area. This property of chlorine dioxide gas allows it to easily penetrate and disinfect locations where other fumigant applications such as dry fog is not able to effectively reach.

****!!!!***!!!*** (2017) {Includes CD bond specs for liquid & gas phases.} ***Disinfection using such low-concentration ClO2 gas does not require evacuation of people, and could be used to disinfect room air in the simultaneous presence of people.*** It is demonstrated that chlorine dioxide (ClO2) gas of extremely low concentrations that have no toxic effect to animals has strong anti-microbial activity against infectious microbes, such as bacteria and viruses... The use of ClO2 gas at very low concentrations may open new avenue of disinfection systems of room air without requiring evacuation of people. This review presents the details of the disinfection system of ClO2 gas." "The use of 0.03 ppm ClO2 gas is also useful in prevention of mosquito-related infective diseases, such as malaria and dengue fever, given that this concentration of ClO2 gas has a repellent effect against mosquitoes" "rats exposed to 0.1 ppm ClO2 gas for 24 h/day and 7 days/week for a period of 6 months were completely healthy " "rate of killing increases along with the increase in relative humidity. "

*****!!!!****!!!!*** {Provides excellent definitions of ppm in air vs. liquid, etc} [Helpful note: Molecular weight of Chlorine Dioxide is 67.45] The unit of gas concentration is converted into another unit.

******!!!!****!!!!****!!!*** 2012. {Note: Click "Download full text" and wait. Full text file will download to your computer} "More than half of the ClO2 gas decomposed indoors." Gaseous ClO2 is chemically dissociated by light with wavelengths between 350 nm and 475 nm. They reported that the dominant (96%) dissociation products were ClO and O (atomic oxygen). It is important to take into account whether these dissociation products are toxic to humans. Judging from the short lifetime of O (39 ns), the toxic effect of this chemical, if ever present, would be negligible... High air temperatures and light irradiation accelerated the decrease of ClO2 gas concentration; the latter had the greatest influence. A quicker decay of concentration and greater value of the reaction rate constant of ClO2 were found under irradiated conditions, especially when a UV lamp was used... ClO2 gas concentration was significantly reduced when an evaporative humidifier was employed due to adsorption and a chemical reaction between the gas and the filter in the humidifier. The results obtained from these experiments can be used to predict the indoor concentration of ClO2 gas" "it was concluded that indoor humidity does not affect the reaction of the ClO2 gas" "an aquarium... filled with 10 L(2.64 gal) water was set in the room" "indoor ClO2 gas levels were lower in the room where water was present because the gas dissolved in water" "Ogata and Shibata (2008) reported that ****!! ClO2 gas concentration in virus aerosols is theoretically 0.12 µM when the aerosols are in equilibrium with 0.03 ppm ClO2 gas !!****, based on their revealed Henry’s equilibrium gas constant k = 3.9 × 10−5 mol 1−1 Pa−1. The present experiment showed higher concentrations of ClO2 in the water"

****!!!!****!!!!**** {Taiko} "Can be applied to any space that can be in a closed state or an open state... Can be supplied at a concentration at which the animal can survive but the suspended microorganisms are inactivated. Therefore, the present invention can be applied to a space where an animal exists. More specifically, the present invention can be applied to living spaces (eg, residences, offices), medical institutions (eg, hospital waiting rooms, examination rooms, treatment rooms, operating rooms, anterior rooms, hospital rooms), research institutions, disaster medical facilities (eg, disaster containers, tents), public facilities (eg, stations, airports, schools), vehicles... When the chlorine dioxide gas concentration in the space is set to 0.00001 ppm to 0.01 ppm, there is no problem even if chlorine dioxide gas is continuously supplied. When the chlorine dioxide gas concentration in the space is 0.01 ppm to 0.1 ppm, the time for supplying the chlorine dioxide gas into the space is preferably 10 minutes to 480 minutes, and 15 minutes to 90 minutes. More preferably, it is more preferably 15 minutes to 60 minutes. When the chlorine dioxide gas concentration in the space is 0.1 ppm to 0.3 ppm, the time for supplying the chlorine dioxide gas into the space is preferably 0.5 minutes to 480 minutes, preferably 1 minute to 60 minutes is more preferable, and 2 minutes to 15 minutes is even more preferable."

****!!!!****!!!!**** 2016. Here, we demonstrate that chlorine dioxide (ClO2) gas at extremely low concentrations, which has no detrimental effects on human health, elicits a strong effect to inactivate bacteria and viruses and significantly reduces the number of viable airborne microbes in a hospital operating room. In one set of experiments, a suspension of Staphylococcus aureus, bacteriophage MS2, and bacteriophage ΦX174 were released into an exposure chamber. When ClO2 gas at 0.01 or 0.02 parts per million (ppm, volume/volume) was present in the chamber, the numbers of surviving microbes in the air were markedly reduced after 120 min. The reductions were markedly greater than the natural reductions of the microbes in the chamber. In another experiment, the numbers of viable airborne bacteria in the operating room of a hospital collected over a 24-hour period in the presence or absence of 0.03 ppm ClO2 gas were found to be 10.9 ± 6.7 and 66.8 ± 31.2 colony-forming units/m3 (n = 9, p < 0.001), respectively. Taken together, we conclude that ClO2 gas at extremely low concentrations (≤0.03 ppm) can reduce the number of viable microbes floating in the air in a room. These results strongly support the potential use of ClO2 gas at a non-toxic level to reduce infections caused by the inhalation of pathogenic microbes in nursing homes and medical facilities.

(2010). Chlorine dioxide (ClO2) has a strong antiviral effect, and can disinfect the surface of object and the air in space. In recent study on interaction between ClO2 and protein, ClO2 oxidatively modified tyrosine and tryptophan residues, and the pro-tein was structurally denatured. Since hemagglutinin and neuraminidase of influenza virus A/H1N1 were inactivated by the reaction with ClO2, it is likely that denaturation of the proteins caused inactivation of the virus. A low concentration (0.03 ppm) of ClO2 gas, where people can stay for a long period of time without any harmful effect, prevented the death of mice (0 of 10 mice versus 7 of 10 in controls) caused by infection of influenza virus delivered as aerosol. We review current information based on the efficiency of ClO2 solution and gas, and also discuss the application of ClO2 against influenza pandemics outbreak.