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JACA (Japan Air Cleaning Association)

The Abstracts of the paper carried by the Journal of JACA

vol.55-6(2018/3/31)

Grasp of microbial sterilization characteristics using chlorine dioxide gas

The objective of this study is grasp of the characteristics of sterilization using chlorine dioxide (ClO2) gas, which has been widely used in the U.S. since a few decades ago as an alternative sterilization agent of carcinogenic formaldehyde gas.  First, the humidity dependence of sterilization effect is examined using commercial biological indicators.  As the result, it is confirmed that the more humidity increases, the more sterilization completion CT value decreases.  Furthermore, the grasp of the surviving microbial number in sterilization is investigated.  As experimental results, the linear relationship between the logarithm survival rate under ClO2 gas exposure is confirmed using self-making biological indicators.

The performance evaluation method of air curtain at the entrance of refrigerating warehouse : Part 2

When open the delivery entrance of refrigerating warehouse, the heat convection will be occurred by temperature difference.  An air curtain can reduce the heat convection, and we have reported the evaluation method of heat insulation performance previous paper1).  We have reevaluated to verify the heat insulation performance in 3.7 times larger test room and longer gate opening time as for 10 minutes.  We have observed over 75% of heat insulation efficiency at 25℃ temperature difference in such conditions, as same as previous results.

Thermal and clean performance evaluations of the operating room air-conditioned by dual heat control systems

Surgery staffs who directly assist the surgeon and circulating staffs who support surgery staffs and monitor the patient have different thermal requirements.  Dual heat control air- conditioning systems are proposed in order to provide double individual thermal environments in an operating room.  One of these air-conditioning systems covers surgery staffs and its inlet-temperature is controlled to be constant.  The other one covers circulating staffs and its inlet-temperature sometimes waves to keep the temperature of the area where the thermal sensor is set constant.  In this system, even if the inlet-temperature waves more than 10℃ difference, the temperature of circulating staffs’ working area waves only a few degrees difference.  The performances of these systems have been made clear by CFD simulation and real-size-mock-up-model experiments.

Dust loading test with super jet mill

Performances of mid- to high- efficiency filter are evaluated based on JIS B 9908 Type 2 and Type 3.  However, the filter performances obtained by evaluation based on the standard are not in good agreement with filter performances in service due to difference in particle size distribution.  Therefore, there are great interests in reproduction of filter performances in service in laboratory tests. In this study, performance evaluations based on JIS B 9908 are carried out with super jet mill instead of ejector.  First, particle size distribution of loaded particle by super jet mill has been investigated and compared with loaded particle by ejector.  As a result particle size distribution wasn’t effected by air pressure set for this study of super jet mill and mode diameter was 1.1μm.  These diameters are smaller than loaded particle by ejector around 2μm.  These tests have showed super jet mill can load smaller particle than ejector.  Second, performance evaluations of mid-to-high efficiency filter has been carried out with super jet mill.  These test results revealed air flow resistance reached final air flow resistance with smaller amount of dust than the test results with ejector. Performance evaluations of pre-filter have been also carried out with super jet mill.  These test results showed it is difficult for jet mill specifications for this study to evaluate performances because high concentration and a large amount of dust are loaded with vigor and there have the potentials to change particle size distribution and dust concentration of loaded dust during evaluation tests.  These phenomena make accurate performance evaluations of pre-filter with jet mill difficult.

Performance improvement by optimizing internal structure of nanofiber filter-media

Performance improvement of filter-media by using various nanofiber is underway, because water-resistance and time-related deterioration of cellulose nanofiber (CNF) is not clear yet, and PTFE (Poly Tetra Fluoro Ethylene) nanofiber is not reasonable by comparing with commercial glass fiber-media.  Because wet-laid is superior to dry-laid and meltblown in controlling the filter-media structure, we have done a trial of wet-laid filter-media by using glass nanofiber which isn’t being used for commercial filter-media, with changing fiber mixing ratio and dry temperature.  As a result, the trialed filter-media has higher Qf value (Quality factor) and smaller MPPS (Most Penetrating Particle Size) by comparing with commercial filter-media.  This research will be useful for improvement and development of filter-media.

Studies on the actual conditions of the odour substance pollution in the residence and its countermeasure technique

In recent years, odour substance contamination in houses has been regarded as one of factor that impedes daily comfort.
Dead bodies, fire accidents and odour substances derived from pets may remain in the room for a long period of time, so the housing management companies may not be able to rent or sell until the same odour contamination is eliminated.
In this research, in order to solve this problem, at first we quantitatively investigated the actual condition of odour substance contamination in houses.  Specifically, we’ve measured odorant concentrations in houses where dead bodies were left for a long time.  Next, the amount of odour substances generated from tatami mats and wallpapers collected from the same house has been determined by a small chamber test.
As a result of actual survey, aldehydes and fatty acid have been detected in Japanese room B where the strongest odour intensity caused by corpses.  In the chamber test, the same substance as the odour substance have been detected in Japanese room B was detected from tatami.  On the other hand, odour substances were hardly detected from the wallpaper in the same room. Furthermore, by chamber test under heating conditions, the emission of odour substances from tatami mats was promoted, and effective heating conditions for bake-out could be obtained.

Study of influence on indoor air quality environment by stack effect

Stack effect occurs in tall buildings during the winter.  Stack effect is thermal convection phenomenon that generates upward flow due to the buoyancy of air.  This effect brings various problems in indoor environment.  For example, intrusion of cold air, wind noise, opening and closing failure of door etc.  Recently, also the other problems on indoor air quality by stack effect became to be recognized.  Contamination that generate in lower floors is transported to upper floors by airflow caused by stack effect.  However, these trouble about indoor air quality has known around only workers like building administrator or building designer.  There is few researches that stack effect associate with indoor air quality environment.  In this research, an advance model of stack effect was developed.  This model is based on fluid dynamics and, this enable the prediction of unsteady phenomenon like a mass transport.  So, this model can predict air advection route and amount of advection air each room in building.  The new method is applied to the building model which has 10 stories and a elevator shaft or stairwell.  As a result, the phenomenon known among workers is enabled to simulate by new calculation model.  By comparison of shaft model and stairs model, it was found that the difference of air flow in shafts influences indoor air quality.  In addition, this paper introduces the application of natural ventilation method using the stack effect to improvement of indoor air quality.

Practical application of automatic and continuous measurement instrument for acidity (pH) and chemical ions in PM2.5
―Measurement of acidity (pH) of surface on PM2.5

Recent years, many studies point out that the fine particles matter less than 2.5 µm has more damage to human body.  Especially, the measurement of acidity in PM2.5 is essential for investigation of risk to human health.  In this study, an automatic continuous measurement instrument of chemical ionic components and acidity in PM2.5 was developed.  The developed instrument consists of an inertial impactor, a parallel plate type diffusion scrubber for removal of air pollution gases such as NO2, SO2, NH3, HCl and HNO3, and a mist chamber for collection and extraction of PM2.5.  The sample solution of PM2.5 collected and extracted by mist chamber is introduced to ion chromatograph. Chemical ions such as Na+, NH4+, K+, Mg2+, Ca2+, F, HCO3, Cl, NO3 and SO42- in the sample solution can be separated and determined by ion chromatograph with concentration column. The acidity of PM2.5 solution is also measured by micro pH electrode. Sequencer controls air pumps, liquid pumps and ion chromatograph for allowing measurement of concentration of chemical ions and acidity in PM2.5 every hour automatically and continuously.
Water content of the aqueous phase on PM2.5 is necessary to calculate pH of the aqueous phase on PM2.5 (In-situ Acidity) by H+ concentration of PM2.5. According to the method estimating water content of the aqueous phase on PM2.5 from the concentration of deliquescent materials such as (NH4)2SO4, NH4NO3 and NaCl, water content of the aqueous phase on PM2.5 collected in Yokohama from July 25 to August 7, 2015 ranged from 1 to 46μg/m3, and its average was 11±8 μg/m3(n=158). As the results, pH of the aqueous phase on PM2.5(In-situ Acidity)ranged from -2.1 to -0.7, and its average was -1.4±0.3(n=158). It was found that the aqueous phase on PM2.5 was highly acidic.

Closed recirculating land-based aquaculture system

Closed recirculating land-based aquaculture system is one of the industrial facility for food production.  In this technological review, the characteristics of that system are explained including our research: 1) growth enhancement and maturation arrest of the farmed fish by environment controls that cannot be realized in natural water environment, 2) combined food production, e.g., aquaculture and hydroponics with material recycling and 3) utilization of renewable energy and industrial heat waste.

Analysis of infection spread with agent simulation

Agent simulations make it possible to analyze the emergent social phenomenon based on the microscopic activity of individuals.  Proper modeling of the target phenomena is required in order to derive perception from the simulation results.  Several study cases of infection spread with the agent simulation have been introduced.  Epstein and Axtell (1996) have proposed Sugarscape model and have used it to simulate the infection spread and the acquisition of immunity.  Tanuma and Deguchi (2007) have developed Spot Oriented Agent Role Simulator (SOARS) and have evaluated the effect of the school closure on the infection spread.  Nagano et al. (2016) have used artisoc, which is one of the multi agent simulation tools, and have investigated the site of occurrence of the infection in the detailed plan of the building.  The agent simulations help a lot to offer numerous suggestions how to control the infection spread.