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JACA (Japan Air Cleaning Association)

The Abstracts of the paper carried by the Journal of JACA

vol.58-5(2021/1/31)

Characteristics of hypochlorous acid

Hypochlorous acid is characterized by not only an oxidizing agent but also a weak acid (pKa=7.5). Oxidizing power of hypochlorous acid is due to an electrophilic action of Cl (Cl+) of the molecule. Depending on the solution pH, hypochlorous acid (HOCl) is dissociated into OCl and H+. Interfacial behaviors of undissociated, i.e., electrically neutral HOCl differ from those of ionized OCl. HOCl exerts a strong antimicrobial action because of its permeability across cell membrane. In addition, HOCl can decolorize pigments and deodorize flavor components sorbed in plastics and elastomers. On the other hand, OCl has a cleaning power against organic soils on a solid surface owing to oxidative degradation and replacement. The use of concentrated alkaline sodium hypochlorite solution gives cleaning and disinfecting effects simultaneously by actions of OCl in conjunction with OH. Furthermore, HOCl is volatile and gaseous HOCl can contribute to the inactivation of microorganisms and viruses in a room space.

Generation of hypochlorous acid water by electrolysis and application examples

Aqueous solutions containing hypochlorous acid (HClO) have different names depending on the concentration and pH. In this paper, the generation method of three types of HClO water included in JIS B 8701 (pH2.2-8.6, HClO:10-100mg/kg), the specifications, and the HClO content rate of the solutions are presented. The HClO water have bactericidal and viral inactivation effects while ensuring its safety as a food additive. The HClO water (40mg/kg) have a higher bactericidal effect than sodium hypochlorite solution (1000mg/kg). Furthermore, the maximum usable volume of HClO water has been estimated considering the amount of chlorine gas generating by the HClO water in relation to the outside air volume.

Bactericidal effect of fogging weak acid hypochlorous solution and case study in the flooded area

Weak acid hypochlorous solution (WAHS) has used for the purpose of disinfection and deodorization in the medical, welfare and food field. We research the bactericidal effect of fogging WAHS against attached bacteria. We already know this effect is closely depend on the concentration of fogging WAHS. Considering torrential rain in western Japan in 2018, the number of falling bacteria inside the damaged house are about 100 times that of a normal room condition. These falling bacteria are suppressed by spraying or ultrasonic atomizing. In addition, WAHS wiping has higher bactericidal effect against attached bacteria and fungi than tap water. It is considered that WAHS is useful for hygiene control in the shelter and implementation of safe recovery efforts by volunteers in flooded area during infectious disease epidemic.

Development and application for humidification and decontamination system using two-fluid nozzle

We develop a humidification and decontamination system using two-fluid nozzle, which system can be installed as a building equipment. This paper explain the overview of the system, the installed example in an actual facility, and the operation effects. The system is installed in a nursery of a commercial facility and can be used as humidification in the daytime and decontamination in the nighttime. These operation conditions are determined via contamination tests with a biological indicator in the actual location. The adherent bacteria are investigated 3 years after the operation is started to evaluate the operational effects. Because the decontamination operation is performed regularly, the number of adhered bacteria is lowered in general. After the decontamination, the number of bacteria decreased further, and their decontamination ability is confirmed.

Humidifying air purifier for business use utilizing hypochlorous acid water

As new coronavirus infections spread worldwide, concern about indoor air quality is growing. We developed Pure Washer, a humidifying air purifier for business use, considering that the needs for a safe indoor environment extend to public spaces. This product is equipped with an air washer that can perform humidification, deodorization, and air cleaning. The technology has the advantages of reducing ventilation through deodorization, eliminating airborne viruses, and preventing contaminants from accumulating on the surface like filters. Furthermore, by using hypochlorous acid water generated within a device, contamination around the water by microorganisms can be suppressed, so that it can be used safely in the living space. As one of infection prevention measures, this paper introduces humidifying air cleaning mechanism using hypochlorous acid water, performance evaluation results, and utilization examples of hypochlorous acid water.

Deodorant effect to sulfur compounds using hypochlorous acid water

To estimate the deodorization mechanism by hypochlorous acid water, the removal test of mercaptans has been conducted. The higher amount of free residual chlorine as the index of acidity strength of hypochlorous acid, the better removal performances have done. When methyl mercaptan gas is injected into a closed container filled with moist air, including an aerosol of acidic electrolysis water (50mg/L), 90% of the initial concentration of 1ppm of the gas is instantaneously removed, and the formation of methane sulfonic acid has been confirmed. The estimated reaction pathway is as follows: CH3SH→CH3SSCH3→CH3SO3H. When air containing methyl mercaptan (0.003ppm) is ventilated with moist air, including an aerosol of less harmful acidic electrolyzed water (5mg/L), neutralization and deodorization are achieved, with slight odor of hypochlorous a