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JACA (Japan Air Cleaning Association)

The Abstracts of the paper carried by the Journal of JACA

vol.59-6 (2022/3/31)

Analysis of nanoparticle loading characteristics of HEPA filter

Typical air filter system for indoor ventilation has been used as a combination of the pre-filter, medium-performance filter, and high-performance (HEPA) filter. Pressure drop of the HEPA filter, which is located at the most downstream, is dominant for ventilation cost, and it is determined by the deposition of fine particles that penetrated pre- and medium performance filters. Therefore, it is important to analyze the particle loading characteristics against nano- and submicron particles. In this study, high concentration NaCl nanoparticles were generated by the six-jet atomizer and they were challenged to the medium and HEPA filter. Pressure drop of both medium and HEPA filters were measured as a function of loaded particle mass. By changing the MPPS (most penetrating particle size) of the medium filter, we found that increase in the pressure drop of HEPA filter can be described in terms of the MPPS. As a result, it was found that the lower MPPS (high performance) medium filter is preferable for protecting HEPA filter.

Airflow control and effect of down-flow air curtain

Demand for insect repellent equipment is increasing due to the mandatory HACCP. There is a blow-down type air curtain as one of the countermeasure equipment, but it is said that the insect repellent performance is low. Therefore, improvements and experiments were conducted for the purpose of improving performance. As a result, we have established an optimal air curtain airflow control method that achieves an insect repellent efficiency of 90% or more. We report the verification of the air curtain airflow and the results of the insect repellent performance test conducted.

Indoor air pollution by unvented combustion appliances

The indoor formaldehyde concentration at 0 minute has been 21.58μg/m3, and the indoor concentration has increased and reached at 89.08μg/m3 after 50 minutes of with use of a radiant type of kerosene heaters. The acetaldehyde concentration has been 11.98μg/m3 at 0 minutes, and indoor concentration has increased to 38.12μg/m3 after 50 minutes. Furthermore, comparing the indoor concentration of 50 minutes after using the appliances with the initial concentration, formaldehyde has increased more than 4 times, and acetaldehyde has increased more than 3 times.
The initial VOC concentration in the chamber has indicated 113.6μg/m3, 371.5μg/m3 after 10 minutes, 574.7μg/m3 after 20 minutes, 767.0 after 30 minutes of use.
After 40 minutes of use, it has reached at 950.3μg/m3. In addition, due to the heat storage of the kerosene heater. VOCs has been generated from the appliance even after the extinguish, and the indoor TVOC concentration has continued to rise, reaching at 203μg/m3 after 50 minutes and 2418μg/m3 after 60 minutes. Of the 47 VOCs to be measured, 26 substances have been measured, and the substances in which a particularly remarkable increase in concentration has been observed in nonane, decane, octane, undecane, heptane, dodecane, tridecane, tetradecane, 2,4-trimethylbenzene, mp-ethyltoluene, pentadecane, and mp-xylene.

Research on test method of gas removal filter

ISO10121-1 and 10121-2 have been established as international standards for gas removal filters, and the JIS B9901 draft drafting committee has been established to fomulate JIS standards consistent with the ISO standards, and new drafts are being prepared. The proposal consists of JIS B 9901-1 for the purpose of material testing conducted in a small-scale test facility and JIS B 9901-2 for the purpose of testing a filter unit conducted in a large-scale test facility. From the results of JIS B 9901-1 conducted as a material test, Murakami et al. have examined the estimation method of the results when the performance of the filter unit made using the same material has been implemented by JIS B 9901-2 and have showed its validity. The authors have newly developed and manufactured a miniaturized test device shown in the new plan JIS B 9901-1. A gas removal performance test of the adsorbent has been conducted using this device. As a result of the test, the VOCs removal rate has been 60% for activated carbon and about 10% for zeolite. Moreover, the gas removal performance of the sample obtained by adding the adsorbent to the above-mentioned activated carbon has been reduced to about 40%.

Deterioration characteristics of removal performance by activated carbon for pollution materials

As people’s standard of living improves, indoor environmental comfort is required, and odor pollution, in particular, is in need of a solution.
Currently, activated carbon with an agent attached to it to increase its removal efficiency is in wide-spread use.
However, there are still many unknowns regarding the adsorption performance and degradation of contaminants on the attached activated carbon.
In this study, we will focus on the type, amount, and method of the additive of the activated carbon, and conduct basic research to develop a new type of activated carbon that can retain odorants efficiently and for a long period of time.
As a result, the adsorption characteristics of non-added activated carbon for each ammonia concentration (3, 10, and 25 ppm) have just been determined. In addition, the adsorption characteristics of ammonia, acetaldehyde, and formaldehyde for different additive methods have been clarified.
From these results, we have clarified the ammonia, acetaldehyde, and formaldehyde adsorption properties of the prototype attached activated carbon.

Electrostatic control in clean rooms

Semiconductor devices (LSI) and Liquid crystal displays (LCD) are produced in an ultra clean environment in order to prevent contamination from fine particles in the air. And also, Static electricity causes electrostatic problems, such as the adherence of fine particles in LSI and LCD production processes. Therefore, the clean rooms for producing LSI and LCD require technologies for eliminating static electricity while maintaining a production environment to be even higher than the integration level of electric circuits on LSI and substrates for LCD. This paper describes: 1) problems caused by static electricity in clean rooms, 2) technologies for solving them and their problems, and 3) two types of advanced ionizers used in clean rooms for solving these problems.

Physics & virology properties and behavior in built environment of SARS-CoV-2

The present article describes the current spread circumstance of COVID-19 pandemic, corona virus and SARS-CoV-2, dose-response relationship, physical & biological laws of SARS-CoV-2, and behavior of SARS-CoV-2 in indoor environment. The key preventions are behavior change such as avoiding 3Cs, wearing a mask and keeping social distancing. Furthermore, since the main generation sources of SARS-CoV-2 are infected person indoors and SARS-CoV-2 are particulate matters, dilution by ventilation and the filtration with a high efficiency filter, and ultraviolet germicidal irradiation are effective measures.