Comparison of Multiple Systems for Laboratory Whole Room Fumigation

Abstract

Fumigation of high-containment microbiology facilities is an international requirement and in the UnitedKingdom this process is still commonly undertaken using formaldehyde vaporization. Formaldehyde usage is simple and inexpensive, but concerns exist over its toxicity and carcinogenicity. Alternative fumigants exist, although independent, parallel comparison of these substances is limited. This study determined the level of biocidal efficacy achievable with formaldehyde and compared this with other commonly used fumigants. Three different hydrogen peroxide-based fumigation systems were evaluated (two vapor and one dry-mist methods), along with true gas systems employing ozone and chlorine dioxide. A range of challenge microorganisms was used at different room locations to assess the efficacy, usability, and safety of the fumigation equipment. These microorganisms included Geobacillus stearothermophilus, Clostridium difficile, Mycobacterium fortuitum, and Vaccinia virus. Only chlorine dioxide and formaldehyde fumigants gave consistently high levels of antimicrobial efficacy across all bacterial challenge tests (typically greater than a 5-log reduction). All systems performed similarly against Vaccinia virus, but variable results were noted for Geobacillus, C. difficile, and M. fortuitum for the hydrogen peroxide-and ozone-based systems. The study also revealed inconsistencies in system reliability and reproducibility, with all fumigant systems aborting midcycle on at least one occasion. In contrast, formaldehyde fumigation was confirmed as extremely reliable, largely because of its simplicity (liquid plus hot plate). All the fumigants tested have UK workplace exposure limits of 2 ppm or less, yet residual fumigant was detected for the formaldehyde and hydrogen peroxide systems following cycle completion, even after room aeration. Articles

The role of ‘no-touch’ automated room disinfection systems in infection prevention and control

“…The HPV system was faster than the aHP system, as in the study by Fu et al 70 These results indicate that HPV is faster and more effective for biological inactivation than aHP. 69,70,75 However, these studies were not performed in a clinical setting and did not evaluate surface decontamination directly or impact on pathogen transmission.…”

“…Recent evidence published by Pottage et al and others indicating that catalase-positive bacteria are less susceptible to H 2 O 2 -based NTD systems than bacterial endospores provides a further reason to use stringent challenges for these systems. 70,75,79,80,125 There is a parallel with standards for liquid hospital disinfectants. For example, the EPA requires a hospital disinfectant to achieve a >6-log 10 reduction of certain vegetative bacteria in vitro.…”

“…For example, H 2 O 2 vapour systems are more able to penetrate increasing levels of organic soiling than aHP. 70,75 However, few studies have evaluated how the level of precleaning influences the efficacy of NTD systems in situ. One study of HPV and one study of UVC demonstrated significant reductions on pathogen contamination when the NTD systems were applied without pre-cleaning, suggesting that precleaning protocols could be truncated.…”

“…12 Chlorine dioxide has a high level of efficacy against a range of pathogens. 75 However, concerns about safety and material compatibility mean that it is unlikely to be used in healthcare settings. 75,98 'Fogging' with various chemicals, including super-oxidized water and solutions of H 2 O 2 mixed with other chemicals, has been evaluated.…”

“…75 However, concerns about safety and material compatibility mean that it is unlikely to be used in healthcare settings. 75,98 'Fogging' with various chemicals, including super-oxidized water and solutions of H 2 O 2 mixed with other chemicals, has been evaluated. 17,18,115e120 These systems are limited by directional introduction of the active agent and consequent non-homogeneous distribution, and the potential for the accumulation of large volumes of chemicals that require postprocess removal, with associated risks to operators.…”