"At a given ClO2 gas concentration, ClO2 residues on tomatoes significantly (P < 0·05) increased with increasing RH, and there were close correlations between log reductions of pathogens and ClO2 residues on tomatoes."

"Pathogen populations reduced more under 90% than under 50 and 70% relative humidity. No significant differences in reduction levels between 50 and 70% relative humidity."

****!!!!****!!!!**** "In comparison, chlorine dioxide required an exposure period of 60 min to reduce both B. atrophaeus and G. stearothermophilus by 5 logs." "For chlorine dioxide treatment, increased the relative humidity within the chamber to 65%." "ClO2 tests at 25°C due to problems with condensation at 35°C on the Minodox/ ClorDiSys/ PrimaTec) photometer lens in the ClO2 generator (external to the chamber and therefore at a lower temperature) causing the decontamination cycle to continually abort." "Recommended (by ClorDiSys) biological indicator to validate processes for ClO2: B. atrophaeus." ***** "The increase in the humidity above that normally found in the chamber may allow the water vapor to microcondense onto surfaces and penetrate into a dried population of microorganisms. Chlorine dioxide readily dissolves in water; if this water has condensed onto the surfaces and surrounds the spores, then there will be greater penetration into the coupons and a quicker kill... Initial slow reduction in survival fraction may be a lack of penetration of water vapor during the preconditioning and conditioning phases, followed by absorption of the ClO2 into the dried spore population on the coupons." [???]

{Applications at various Relative Humidity} Based on past remediation efforts, it is generally accepted that in order to achieve adequate kill, chlorine dioxide fumigation of a building requires a minimum relative humidity (RH) of about 65%, with a target ClO2 concentration and exposure time of 750 ppmv for 12 hours, for a total concentration of 9000 ppmv-hrs (CT). Other researchers have recommended a RH of greater than 70% for ClO2 concentrations between 125 and 10550 ppmv. Under current EPA guidelines, applications of ClO2 for building remediation require 75% relative humidity and an exposure of 9000 ppmv-hrs. {Includes info on corrosion mitigation.}

"Variations in RH [relative humidity] have great effect on the solubilization of ClO2 gas on tomato surfaces considering that ClO2 residues on tomatoes increased with increasing RH. Also, the amount of ClO2 residues on tomatoes is positively correlated with the level of inactivation of pathogens."

****!!!!****!!!!**** "Spray-applied solutions of ClO2 at measured concentrations of 3000−4000 ppm were effective against B. anthracis on several nonporous building surfaces but ineffective or not consistently effective on porous surfaces and soils" "If porous materials (carpet and particle board) were immersed in a 1000 ppm, 6 LR of B. anthracis was achieved. Improved effcacy through immersion at a lower concentration suggests that the limited effcacy of spray-applied liquids could be due to spray-application parameters (e.g., droplet size or insuffcient number of applications). ****!!!!!*** Perhaps ClO2 in the aqueous phase could be lost through volatilization from spray droplets or from the wetted surface during the application." "Aqueous solutions of ClO2 5000− 6000 mg/L were produced via easy-use product with sodium chlorite and sodium bisulfate. When applied as a ***fog,*** the ClO2 solutions were effective on a number of materials." "spore populations of B. subtilis... effective decontamination using ClO2 gas levels ranging from 350 to 750 ppm. In a series of six small-chamber experiments conducted at either 100 or 200 ppm of ClO2 (75% RH, 24 °C; CTs ranging from 2 to 12 h), several building materials were effectively decontaminated" "aqueous ClO2 can be generated electrochemically using sodium chlorite and sodium bromide." "relatively cooler temperature that may be encountered in a subway system (11 °C), the lower temperature greatly diminished the decontamination effcacy128 In this same study, lowering RH from 75 to 50% (at 24 °C) also greatly reduced effcacy."