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??? ]

"It has the effect of deodorizing eight major odors: ammonia, methyl mercaptan, hydrogen sulfide, methyl sulfide, trimethylamine, methyl disulfide, styrene, acetaldehyde."

****!!!!****!!!!*** (2021) "To satisfy the 8-h Time Weighted Average (TWA) maximum exposure limit of 0.3 mg/m3 for ClO2 (OSHA 2020), ClO2 disinfection in the bicycle room was performed using 400 mL ClO2 solutions (at 250 mg/L)."

****!!!!****!!!!**** (2020) "hospital infectious disease ward in Taiwan" "For studying the factors affecting the disinfection efficiencies of the two treatment protocols, the relative humidity and temperature in the SR and DR were detected with a humidity temperature... A Q-TRAK IAQ Meter... was used to detect the airflow velocity and CO2 concentration. The luminance was measured using a TES-1335 Digital Light Meter (TES Electrical Electronic Co., Taiwan). Afterward, the number of individuals in the room on each sampling occasion was counted and recorded.""By comparing these two studies, it was found that the efficiencies were very different because in the present study, the space was not closed during the disinfection and people can come in and out freely."

****!!!!****!!!! {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."

"American foulbrood disease is an economically important, reportable bacterial infection of honey bees" "Sporicidal efficacy was dependent on treatment time and gas concentration with effective ClO2 concentrations of 645 ng/ml for 30 min, 195 ng/ml for 1 h, 21 ng/ml for 2 h, or 16 ng/ml for 4 h. Treatment of surfaces with 230 ng/ml ClO2 for one h or 195 ng/ml ClO2 for 2 h completely inactivated P. larvae spores."

****!!!!****!!!!**** "ClO2 decreased from 10 mg/m3 to 0.8 mg/m3, and the degradation time was 81 min. Reduced to 0.3 mg/m3, degradation time is 96 min; Reduced to 0 mg/m3, the degradation time was 2 h.10 mg/m3 disinfection dose for 30 min, and the total number of bacteria and the number of fungi were 94.6% and 92.1%, respectively. Conclusion ClO2 disinfected the pit air spray with a concentration of 1 000 mg/L and 10 ml/m3, and the sterilization effect was the best for 30 min."

****!!!!****!!!!*** "aerosol spray was applied to 50 mg/L chlorine dioxide at a dosage of 20 ml/m3 for 90 min, and the extinction rate of natural bacteria in indoor air was 91.58%, the extinction rate of natural bacteria in air was 82.00% with 10 mg/m3 ozone fumigation for 60 min, and the extinction rate of natural bacteria in air was 82.00%. The three disinfection methods have a killing effect on natural bacteria in the air, but the chlorine dioxide aerosol spray method has the best effect and the dosage is low."

"For indoor air pollution problems, research scholars have developed chlorine dioxide sustained-release air purification device. When chlorine dioxide release rate is 7.4 mg·h−1 and relative humidity is in the range of 29–31%, 59–61%, and 89–91%, it can effectively purify hazardous substances like formaldehyde generated from interior decoration " "developed a new type of sustained-release solid chlorine dioxide disinfectant for drinking water treatment. Compared to traditional chlorine dioxide disinfectant, it had the advantages of stability, convenient storage and transportation, and long-acting time, etc."

(2020). ****!!!!****!!!!****

(2018) “FarmeTok (Medistick/Puristic) kindly provided by Purgofarm" "ClO2-releasing hygiene stick showed the very strong inhibition of bacterial growth but had different inhibitions to the bacteria above 96.7% except for MRSA of 90% inhibition. It is difficult to explain why the MRSA were not inhibited less than others at this point. It can be only suggested that more releasing ClO2 should be essential to kill or inhibit the MRSA. B. subtilis, S. agalactiae, S. pyogenes, E. coli O157:H7, S. typhi (S. enterica serotype typhi) and S. marcesence were inhibited over 99%. It can also suggest that the inhibition may not be affected by the Gram positivity and Gram negativity." [****Note: The measurement method used here seems unclear: "the released ClO2 gas concentration was 13 ppmv/hr"]

****!!!!****** "UVC irradiance could not be detected in all the cases. For analyzing the UV content at the short distance, the measurements were conducted at the distance of 10 cm. Negligible amounts of UVA and UVB were detected at 150 and 200 cm from all CFLs." "In order to compare UV irradiance in three angles (0, 45, and 90), one-way ANOVA indicated that difference between three angles was not significant statically"

****!!!!****!!!!**** (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"

The results show that:when the concentration of chlorine dioxide gas is 0.3mg/m3,the sterilization time is 60min,the sterilization time period is from 20∶ 00to 21∶00(under fluorescent lights),sterilization rate to the atmosphere can reach 99.8%,and the sterilization rate to the objects' surface can reach 93.9%.Under the premise of human activity,it is the optimal sterilization conditions for hospital wards.

****!!!!**** "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."

An allergen inactivating agent for preventing allergic manifestations or alleviating symptoms by reducing antigenicity of an allergen through contact with the allergen includes dissolved chlorine dioxide as an active ingredient. "0] For the concentration of chlorine dioxide that reduces the antigenicity of the allergen, from 0.05 ppm to 1 ppm is preferable, from 0.1 ppm to 1 ppm is more preferable, and from 0.1 ppm to 0.6 ppm is still more preferable. When the concentration is above 1 ppm, a safety problem may occur, and when below 0.05 ppm, effects as expected may not be obtained. Example of the forms of application include a nasal lavage fluid, collyrium, eye-drop, nasal solution (nasal spray), spray for throat, liniment for throat, and gargle. Specifically, it is possible to prevent allergic manifestations and alleviate allergic symptoms, by inactivating the allergen with the dissolved chlorine dioxide and washing down the allergen with the agent as wash solution, and thus by suppressing the amount of the allergen to a threshold or less. For example, an appropriate amount of the dissolved chlorine dioxide (aqueous solution of chlorine dioxide) having the concentration of from 0.1 ppm to 0.6 ppm may be applied externally as the nasal lavage fluid, collyrium, gargle or the like, 3 to 6 times per day." "to thereby obtain 1,000 ml of an aqueous solution of chlorine dioxide including chlorine dioxide gas dissolved therein, sodium chlorite, and sodium dihydrogenphosphate."

****!!!!****!!!*** "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."

"The air disinfection simulation field test shows that the atomization concentration of the disinfection machine is 250ppm. Chlorine dioxide disinfectant, the use amount is 20ml/m3, the killing rate of 15 Staphylococcus albicans in the air is 99.99%."

*****!!!!****!!!!*** {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.

{Study mentioned with Chlorine Dioxide} "viruses... exposed to fogging from a machine capable of generating fogs at 30ml/min until desired concentrations were achieved. The chlorine dioxide (ClO2) exposure was 10 min. ... the ClO2 product only showed reductions of 1.7 log10, 0.6 log10, and 2.4 log10 respectively. However, the exposure times used in the study were extremely short..."

{***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. "

****!!!!****!!!!**** 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.