vol.61-6 (2024/3/31)

Development of PFAS-free air filter media

Perfluoroalkyl substances (PFAS) are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom. In air filtration applications, PFAS are commonly used to impart water and oil repellency to filter media. However, the carbon and fluorine in PFAS are strongly bonded, so they are not easily decomposed, and furthermore, there are concerns about adverse health effects. In this study, PFAS-free air filter media are developed using a water repellent composed of fluorine-free hydrocarbon polymer. The newly developed filter media have the equivalent basic media properties (filtration performance, tensile strength, stiffness and water repellency) to the conventional filter media containing fluorinated repellent. On the other hand, their behaviors toward oil droplets are different.

A study of bio-decontamination of air filters using vaporized peracetic acid

Many microorganisms and viruses are present in the general air environment and they must be removed or sterilized in order to create a sterile environment. Air filters used for the purpose of removing microorganisms and viruses in the air require regular bio-decontamination. In this study, we report on the bio-decontamination of air filters using peracetic acid.

Analysis of high-performance filter decontamination using functional mist

In medical institutions such as pharmaceutical factories and biological research facilities, high spatial cleanliness is required to prevent from the contamination and to ensure the safety of workers. In order to realize such clean space, ventilation systems equipped with high-performance air filters are often used. Especially in the bio-clean space, which aims to prevent microbial contamination such as viruses and bacteria, the prevention of contamination of the air filters themselves is also an important issue. When the air filter is used continuously for a long time, airborne bacteria and microorganisms existing in the atmosphere also accumulate on the filter surface, and their growth occurs on the filter surface. Such bacterial growth not only causes deterioration of the filter, but also requires maintenance such as filter replacement because the filter itself becomes a new source of contamination. Therefore, chemical treatment using various chemicals is performed to remove bacteria deposited on the surface of the air filter, that is, to perform decontamination. For example, liquid decontamination agents have a high decontamination effect, but there is a problem that the load on the filter media is large, and decontamination with vapor also has problems such as environmental impact, corrosion, and low sterilization rate. Therefore, in the study, we examined a decontamination method of air filter using functional mist.

H₂O₂ gas generation method of a practical level using SPC / solid acid method

Sodium percarbonate (SPC) is a white solid that is a 2:3 molar mixture of sodium carbonate and hydrogen peroxide. SPC is mainly used in bleaching agents. In this study, we have attempted to release hydrogen peroxide (H₂O₂) gas from SPC. Simply heating SPC causes decomposition of the H₂O₂ gas itself, making it impossible to extract high-concentration gas. To solve this problem, we have discovered a technique that suppresses the self-decomposition of H₂O₂ by heating a mixture of SPC and solid acid, and generates H₂O₂ gas at a practical level even at relatively low temperatures. Here, we report the usefulness of solid acid addition, the heating temperature, and the optimum conditions of solid acid ratio for H₂O₂ gas generation from SPC.

Particle measurement system using autonomous mobile robots

FFUs in cleanrooms are often operated at a constant speed, that makes the room cleaner than necessary and consumes a lot of electricity. To optimize the operation of FFUs by monitoring the cleanliness of broad areas of cleanroom, we have developed a system that automatically measures particles in a cleanroom by combining a particle counter and autonomous mobile robots.
We have measured the amount of dust emissions by operating this system, and verified that the amount of dust emissions from this system is sufficiently small compared to manual measurements. And we have studied a method using this system to control of FFUs, and developed a system that changes the rotation speed of the FFUs according to the measurement results.

Study on particle generation and three-dimensional motion analysis during operation in cleanroom

Research on particle generation by work assuming operation in cleanroom has been carried out until now. However, no attempt has been made to evaluate the relationship between particle generation and work intensity by obtaining from the numerical values of displacement and acceleration. In this paper, the work was done in clean booth, and particle generation was measured. At the same time, work intensity of operation was quantified non-contact manner using the optical motion capture. Measurement was body-derived particle and breath-derived particle. As a result, both body-derived and breath-derived particle generation tended to increase in a direct proportional to the work intensity. Though the difference by smoking existence was little in body-derived particle generation, that breath-derived particle generation tended to be about quintuple more in smokers. At rest, breath-derived particle accounted for more than half of total. And as the work intensity increased, body-derived particle generation became dominant.