Negative Air Ionization Research Articles

Enhanced removal of viral aerosols using nanosilver/TiO2-chitosan filters combined with a negative air ionizer

The presence of airborne viruses in bioaerosols is a significant and ongoing public health concern. In this context, this study aimed to develop a new filter that integrates nanosilver into a TiO2-chitosan matrix (nano-Ag/TiO2-CS) to inactivate the non-enveloped bacteriophage MS2 as a viral aerosol surrogate. The materials were characterized using various techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS). The SEM images showed that the nano-Ag particles were spheres with a high surface area for virus interactions and that the fiber surfaces were covered by nano-Ag, which enhanced contact with viruses. The optimal 5 wt% nano-Ag/TiO2-CS filter combined with a negative air ionizer (NAI) showed the highest viral aerosol removal efficiency, which reached 97 %. The use of an NAI during filtration enhanced the inactivation of the viral aerosols. A long-term antiviral efficacy assessment showed that the nano-Ag/TiO2-CS filter demonstrated robust durability, which is vital for real-world applications. The nanofilter proposed in this work is simple, safe, and cost-effective for inactivating viral aerosols to improve indoor air quality.

High-efficiency carbon-coated steel wool filter for controlling cooking-induced oil smoke

Cooking oil smoke (COS) contains many harmful substances, such as particulate matter, formaldehyde, and phenyl esters. Currently, commercial COS treatment equipment is expensive and requires a large space. Furthermore, a large amount of agricultural waste is generated and is mainly burned onsite, producing large amounts of greenhouse gases and air pollutants. This waste could be reused as a precursor for biochar and activated carbon. Therefore, this research used saccharification and catalytic hydrothermal carbonization to process rice straw and produce compact carbon-based filters (steel wool-C) for removing cooking-induced pollutants. Scanning electron microscopy indicated that carbon layers were coated on the steel wool. The Brunauer-Emmett-Teller surface area of the carbon filter was 71.595 m2/g, 43 times larger than that of steel wool. The steel wool filter removed 28.9%–45.4% of submicron aerosol particles. Adding a negative air ionizer (NAI) to the filter system enhanced the particle removal efficiency by 10%–25%. The removal efficiency of total volatile organic compounds was 27.3%–37.1% with the steel wool filter, but 57.2%–74.2% with the carbon-containing steel wool filter, and the NAI improved the removal efficiency by approximately 1%–5%. The aldehyde removal efficiency of the carbon filter with NAI was 59.0%–72.0%. Conclusively, the compact steel wool-C and NAI device could be promising COS treatment equipment for households and small eateries.

Estimating aerosol particle removal in indoor air by ion-enhanced deposition

Small air ions have the ability to charge airborne particles, thereby increasing their accumulation on surfaces. Indoor air purification by applying ionization uses electrostatic particle deposition. Respiratory pathogens, including viruses and respiratory droplets carrying viruses or other pathogens, represent bioaerosols, whose particle size distributions contain increasingly larger proportion of fine and ultrafine particles, as the evaporation process proceeds. We have generated two model aerosols: the nebulized NaCl solution, resembling human saliva, and the cigarette smoke, having relatively low water content. We have conducted real life experiments of such surrogate aerosol particle deposition without ionization, using bipolar ionization, as well as using unipolar negative air ions. Particle number concentrations have been measured in the 10 nm–10 μm particle size range. The calculated deposition rates and aerosol particle half-life times were correlated with bioaerosol pathogens based on the core pathogen sizes. Bipolar ionizers emitting equal concentrations of positive and negative ions had low impact to the particle concentration decrease. Intense negative air ionization resulted in pronounced deposition rate increases, particularly in the particle size range of viruses including the SARS-CoV-2. The impact of negative air ionization was most pronounced in the same size range where the deposition rates without ionization were the lowest. Therefore, the results are very promising from the standpoint of air purification and bioaerosol pathogen removal, bearing in mind that the effect of ions will be most pronounced if the unipolar ion rich air stream is directed towards the breathing zone.

Effect of negative air ionization technology on microbial reduction of food-related microorganisms

Negative air ions (NAI) have been shown to have bactericidal effects on various microbial species.Different concentrations of NAI and ozone (106-7x106 NAI cm-3 s−1, 2.20 mg h-1 of ozone or 8 × 106-2x107 NAI cm−3 s−1, 0.02 mg h−1 of ozone, respectively) were studied to determine whether the effect of these treatments on six food-related microorganisms was due to NAI or also to the ozone that forms.Bacillus subtilis, Escherichia coli, and Listeria monocytogenes showed a significantly microbial reduction after the treatments of NAI with a low concentration of ozone, while Pseudomonas fluorescens, Penicillium roqueforti, and Saccharomyces cerevisiae were affected mainly by NAI and higher ozone concentration. It should be noticed that the reduction of the pathogen L. monocytogenes has been 2.17 Log after 72 h treatment to NAI and low ozone concentration.The results proved that ions (NAI) contribute to microbial killing. However, the sensitivity of microbial species is different and depends on individual parameters of the different microorganisms.NAI technology with low ozone production can be rapid, green, and low-cost and it can represent an alternative to the use of chemicals for the sanitation of air and surfaces in the food sector in order to reduce microbial contamination.

Recovery after effort is essential in maintaining optimal physical condition

Playing a sports game at a competitive level requires considerable physical effort that can only be sustained by excellent physical condition. The effort provided during both training and official competitions must be permanently in the attention of the specialised coach, who should be primarily concerned with preventing excessive fatigue in athletes. A clinical form of chronic pathological fatigue (an imbalance of the whole body, which strongly affects both the physical and mental spheres) is caused by overtraining. Modern means of tracking physical parameters in real time allow the coach to correctly dose exercise intensity as well as the frequency and length of the necessary breaks. The coach also has modern means of restoring the functional systems used during exercise, while being aware that these systems recover at different time intervals. The correct relationship between the recovery process and the recovery time of energy sources is essential in the effectiveness of the athlete’s body recovery technique. The proper load-recovery ratio is the key to the training process, and the decision on the recovery procedure will affect the physical condition of athletes. In the recovery process, specialists can use relaxation techniques, oxygenation, negative air ionisation, active or passive rest, medication, alkaline diet, massage, sauna, acupuncture, acupressure, thermotherapy, cold compression/therapy, vibration therapy, electrostimulation and lymphatic drainage.

Exploring the performance of system changes in Dutch broiler production to balance animal welfare, ammonia emissions and particulate matter emissions with farm profitability

CONTEXTIn response to societal concerns, the European Union set up goals to address the negative impact of intensive broiler production on animal welfare, the environment and human health. OBJECTIVEThis paper aimed to 1) explore combinations of system changes that perform best in terms of farm income, animal welfare, emissions of ammonia (NH3) and particulate matter (PM10) and 2) are robust to changes in society's expectations relating to animal welfare and environmental sustainability. METHODSThe prevailing system in the Dutch broiler market was used as a baseline for evaluating system changes. Animal welfare, NH3 emissions and PM10 emissions were the three external factors chosen for this evaluation. Farm income was quantified by the net return to labor and management (NRLM). Expert knowledge elicitation was used to identify system changes that were likely to be implemented in the baseline system. Combinations were made by selecting system changes from each of the chosen external factors. A deterministic model was used to calculate the effect of each combination of system changes on net return to labor and management. The performance of each combination was evaluated by estimating a benefit-of-the-doubt composite indicator. RESULTS AND CONCLUSIONSResults show that 8 out of 70 combinations indicated a better outcome and were more robust to potential changes in society's expectations relating to animal welfare and environmental sustainability. These combinations included two or more of the following system changes: ‘lower density’ (30 kg/m2), ‘2 types of enrichment’, and ‘daylight’. Furthermore, these combinations included ‘tube heaters’ for the abatement of NH3 emissions, and ‘negative air ionization system’ or ‘ionization filter’ for the abatement of PM10 emissions. To compensate for the decrease in NRLM associated with these practices and abatement techniques, a price premium was required that ranged between 4.8 and 18.5 eurocents/broiler. We conclude that combinations including animal welfare related system changes (lower density, enrichment and/or daylight), tube heaters and an ionization technique performed best and were robust to changes of societal expectations of these external factors. SIGNIFICANCEThe insights obtained from this paper can support decision making in improving the sustainability of current broiler production systems.

Removal of benzophenone aerosols by a rice straw-based activated carbon filter combined with a negative air ionizer

The widely used ultraviolet (UV) protective ingredient benzophenone and its derivatives (BPs) are endocrine-disrupting chemicals and are directly or indirectly released into the environment, posing a threat to human health and environmental ecology. Therefore, this research aims to develop an environmentally friendly purification technology to eliminate BPs from air. Recycled rice straw was used to prepare activated carbon (AC), which was applied to filter BPs in the air. The surface morphology, elemental composition, specific surface area, functional groups, and thermal stability of AC were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), nitrogen adsorption/desorption isotherm analysis, Fourier transform infrared (FT-IR) spectrometry and thermogravimetric analysis (TGA). A negative air ionizer (NAI) was used to enhance the filtration efficiency of the AC filter. The experimental results show that the AC filter can effectively remove BP particles from the air, with a removal efficiency of up to 80% (filter quality factor 10 mm-H2O−1). The NAI further increased the removal efficiency of the filter system to over 99% (the filter quality increased to 60 mm-H2O−1), showing the superiority of this approach. The most important filtration mechanism in this system is the external electric field generated by the NAI.

Feasibility of using bed filters packed with rice-straw-based activated carbon and selected biomass waste for the control of frying fume exhaust.

Open-air burning of rice straw (RS) on sites after harvesting produces tremendous amounts of air pollutants in Southeast Asia. Additionally, cooking oil smoke (COS) from high-temperature frying is classified as "Probably carcinogenic to humans" (Group 2A) by the International Agency for Research on Cancer. To mitigate the air pollution from COS, RS was recycled to prepare activated carbon (AC), which was used as a bed filter (BF) packing material for COS removal, and to our best knowledge, this study is the first one. Besides, a negative air ionizer (NAI) was firstly utilized to enhance the removal efficiency (η) of COS particles. Other biomass waste, including tea leaves (TL), wood dust (WD), rice hulls (RH), and coffee grounds (CG), were also used as packing materials for comparison. Specific surface area and pore volume of the packing materials were determined by nitrogen adsorption/desorption isothermal. Laser airborne particle counters and volatile organic compound (VOC) monitors (photoionization detector) were utilized for real-time recording of the particle and VOC concentration of COS. Economic assessments for the control of COS was also conducted. For submicron particles, the removal efficiency of the BFs ranged from 0 to 98% and the AC filter had the highest quality factor. The NAI remarkably enhanced the η value and filter quality factor. For the removal of particles larger than 2.5μm, all BFs had η > 96%. The removal efficiency of volatile organic compounds (VOCs) (ηVOC) of the test BFs ranged from 18.22 to 90.8%. The AC filter had the largest pore volume (0.432cm3/g) and surface area (877m2/g) among all packing materials, causing this filter to have the highest ηVOC and adsorption capacity (over 28.3mg-VOCs/g-AC). The annual operating costs of the TL, WD, RH, CG, and AC filters were 319.4, 23.3, 29.1, 189.4, and 62.9 US$, respectively. Therefore, using RS to prepare an AC bed filter for the removal of COS is a practical and sustainable strategy for COS control.

Electrostatic precipitator for fine and ultrafine particle removal from indoor air environments

An electrostatic precipitator was evaluated to reduce nanometric and micron-sized particles in indoor air environments. This process consists in a negative air ionizer assisted by a parallel-plate collector. The ionization stage contained four or eight corona needles, which were supplied by a negative high-voltage DC. The collection stage was designed in a plate-to-plate configuration, of which the plates are alternately connected to a high-voltage DC supply and the ground. Fractional efficiency (expressed in number) was investigated using NaCl ultrafine particles and atmospheric aerosol according to different geometric, environmental and operating parameters (concentration, relative humidity, collector and ionizer voltage, collector length, number of needles, and airflow rates). The results are discussed according to particle size. Under optimized conditions (eight needles, 20 cm collector length, −7 kV ionization voltage, 5 kV collection voltage, 1 m/s air velocity), the process revealed high performance levels. The efficiency of particles of 10–25 nm in diameter was 94%, between 30 and 300 nm the efficiency was 99%, while in the most penetrating particle size, the efficiency was 96%, with an ozone concentration at the outlet of the process less than 5 ppbv. This process generated a very low ozone concentration, which is an essential challenge for indoor air treatment. The results confirmed the existence of the partial charging regime for particles less than a few tens of nanometers for which the efficiency was lower. For these particles, the collection conditions (collection time and voltage) had no influence on the efficiency. For larger particles, both the parameters of the charging phase (ion concentration, charging time) and the parameters of the collection phase (collection time and voltage) had a significant influence on the collection efficiency.

Air Ionization in Livestock Buildings – A Review

Abstract Research has shown that microclimate is determined not only by air microparticles, but also by the degree of air ionization. Ions affect the body through the respiratory tract and skin. Exposure of reared chickens to elevated air temperature (37°C–23°C) was found to accelerate the break-down of negative ions compared to temperature lower by 10°C. Negative air ionization offsets the adverse effect of elevated temperature on chickens. Higher (85%) air humidity during rearing of chickens was also observed to destroy negative ions. Research findings indicate that air ionization is an environmental element that contributes to improving performance in broiler chickens. Many studies have also confirmed a positive effect of air ionization on the body weight and health of piglets.

Experimental determination of the dispersion of ions from a point source in the environment

ABSTRACTThe dispersion of ions from a point source has been extensively modelled but there have been very few attempts to experimentally verify the theoretical findings. The main reason for this has been the difficulty of discriminating between cluster ion and charged particle concentrations in the air. In this paper, we describe a novel technique for the experimental determination of the dispersion of ions from a point source in air. Laboratory experiments showed that the lifetime of cluster ions in an aerosol cloud was of the order of minutes. However, once they attached to aerosols, the particles retained the charge for at least 30 min, suggesting that they may be carried long distances in natural winds. A negative air ionizer was used to produce ions and charged particles in an open field in the presence of a steady horizontal wind. A neutral cluster and air ion spectrometer was used to measure cluster ion and charged particle concentrations as a function of downwind distance from the source. The results are broadly consistent with the Gaussian dispersion model for a continuous point source. We estimate that cluster ions can be carried up to a distance of several hundred metres before they fully attach to particles which can then be carried as far as 3–4 km. Therefore, these observations have important bearing on exposure to cluster ions and charged particles downwind of ion sources such as high voltage power lines and busy roads.

Effect of turbulence intensity and particle characteristics on the deposition of submicron particles enhanced by the ionic air purifier

A negative air ionizer (NAI) is a common indoor air purifier for aerosol particles. The turbulence intensity can influence the performance of NAI. Besides, the dielectric constants (p) of particles can affect the electric mobility and deposition of particles in the electric field. Hence, this study aims to exam the difference between the deposition rate of NaCl (p = 6.1) and sucrose (p = 3.3) submicron particles when an NAI is operating under various turbulence intensities.The experiments were conducted in a stainless steel chamber under 50% relative humidity. Polydisperse submicron particles (PSPs) of 30–300 nm and monodisperse submicron particles (MSPs) of 30, 50, 100, 170 and 300 nm were used for testing. In the experiments of particle deposition, the aerosol particle number concentration and size distribution were monitored continuously by a Scanning Mobility Particle Sizer. The decay constant of particle concentration (k) and effective cleaning rate (ECR) were determined from the time profiles of particle concentration.When the NAI was off, k of NaCl and sucrose particles was similar. However, when the NAI was operating, the deposition rate of NaCl particles was higher than that of sucrose particles and the NAI performed better under lower turbulence intensity. Because the coagulation coefficient of PSP was larger than MSP, the decay constant of PSP was superior to that of MSP. The ECR was negatively correlated with particle size and was higher under lower turbulence intensity.Conclusively, the NAI is more efficient in charging particles with higher dielectric constants and performance better under lower turbulence intensity.

Evaluation of oil spraying systems and air ionisation systems for abatement of particulate matter emission in commercial poultry houses

The present study evaluated the performance of four systems for abatement of particulate matter (PM) emission inside full-scaled commercial poultry houses: a fixed oil spraying system (OSF) inside two broiler farms and one laying hen house, an autonomously driving oil spraying vehicle (OSV) in one laying hen house, a negative air ionisation system (NAI) inside two broiler farms, and a positive air ionisation system (PAI) inside two laying hen houses. The systems were evaluated using case-control approaches. At each farm, six 24-h measurements were scheduled of PM 10 , PM 2.5 , ammonia, odour, and carbon dioxide concentrations (the latter for estimation of the ventilation rate and herewith emissions). This paper presents the layout of the systems, compares their performance in practice with that under experimental conditions, discusses improvement possibilities, reports the baseline emission rates of the poultry houses, and discusses the validity of the case-control approaches. The emission reductions of PM 10 and PM 2.5 were: 60% and 53% for the OSF in broilers (at 12 mL m −2 d −1 ), 21% and 31% for the OSF in laying hens (at 15 mL m −2 d −1 ), 32% and 38% for the OSV in laying hens (at 30 mL m −2 d −1 ), 49% and 68% for the NAI in broilers, and 6% and zero for the PAI in laying hens. None of the systems significantly reduced the emission rate of odour or ammonia. On the basis of this work, emission reduction factors of the OSF, OSV, and NAI have been adopted in Dutch regulations.

Combined effect of antimicrobial coatings, gamma radiation and negative air ionization with ozone on Listeria innocua, Escherichia coli and mesophilic bacteria on ready-to-eat cauliflower florets

The objective of this study was to evaluate the effect of a bioactive edible coating combined with a low γ-radiation dose or negative air ionization (NAI) with ozone on the microbiological quality of ready-to-eat cauliflowers. Results showed that each treatment alone was effective on Listeria innocua, Escherichia coli and mesophilic bacteria. After 7 d, treatment with γ-radiation reduced L. innocua and E. coli of 1.8 and 3.6 log CFU g−1 respectively while NAI+ozone reduced L. innocua and E. coli of 2.0 and 2.8 log CFU g−1 respectively. Mesophilic bacteria were reduced of 1.8 log CFU g−1 after γ-radiation and 1.4 log CFU g−1 after NAI+ozone. This study demonstrated that the bioactive coating acts in synergy with γ-radiation, inducing no bacterial growth of L. innocua and E. coli, as well as a control of the growth of mesophilic bacteria during 7 d. The combination of bioactive coating and NAI+ozone induced an additive effect on L. innocua, E. coli and mesophilic bacteria, and suggests potential antioxidant properties of the coating.

Deposition Removal of Monodisperse and Polydisperse Submicron Particles by a Negative Air Ionizer

Indoor particulate matter exposure is one of the main environmental risk factors influencing human health. Previous studies have indicated that the degree of hazards about ultrafine particles was associated with the particle surface area and number concentration. Polydisperse submicron particles (PSPs) contribute most of the indoor aerosol particle number and are usually used for removal testing. However, the behaviors of monodisperse submicron particles (MSPs) are easier to analyze. This study aims to investigate the difference between the deposition removal efficiency of MSP and PSP by the negative air ionizer (NAI) under different settings of freestream air velocity (FAV). The particle-removal experiments were conducted in a stainless steel test chamber under the condition of 50% relative humidity and FAV of 0.56, 1.2 and 2.0 m/s. The NaCl and oleic acid PSPs were generated from a constant output atomizer and the NaCl MSPs (30, 50, 100, 170 and 300 nm) were generated by passing the polydisperse NaCl aerosol through a Differential Mobility Analyzer. The concentration and size distribution of the particles in the chamber were monitored with a Scanning Mobility Particle Sizer (SMPS). The decay constant of particles number concentration, particle removal efficiency (PRE), enhancement factor of deposition rate (EF) and air cleaner effectiveness (ACE) were determined from the SMPS data. The decay constant of particle number concentration increased with the decrease of FAV and decreased with the increase of particle size. Both of the PREs of MSP and PSP were quite high, especially for the smaller particles and under low FAV. The EFs ranged from 4.4 to 115.5 and were proportional to the particle size. In addition, the ACE ranged from 0.57 to 0.96 and increased as the particle size increased. These results give a better understanding of the deposition of 30– 300-nm particles enhanced by the NAI and the influential factors.

Applications to Engineering Physics for Reducing Air Pollution

Taking advantage of modern technology of the macro ionization of air in the air conditioning systems in order to promote the industrial air conditioning systems can be an appropriate way to resolve industrial centers and hospital's pollution, and also resolve monitoring of air in the urban tunnels. Breathing space around us is a mixture of particles and neutral and charged molecules, so by looking back at industrial achievements of tools and instruments of the air conditioners, electrical discharge method is practical and appropriate. In addition to refining of air pollutants, there is also the possibility of removing germs. Macro Air Ionization Technology (MAIT) in the industrial, hospital and urban tunnels is one of the offering methods of increasing healthy air as usual methods in environment. MAIT is a hi-tech equipment for improving air. One of these technologies is Negative Air Ionization Technology (NAIT). In the NAIT equipment air molecules after ionization change Negative Ion Concentrations in the room, tunnels and sheds. The negative ion molecules especially oxygen, will provide a healthy environment for plants growth process. Using NAIT, anions have the ability to conquest the microbes and microorganism. According to the performed research, utilizing the air ventilation modern technologies, have an efficient effect on the quantity and quality of important place as hospitals. For this reason, negative ion injections by MAIT into the air could be a part of research policies in developing and least developing countries for effective exploitation and correction of the Health and Safety Executive (HSE) conditions, as it was the part of basic research policies in last 40 years in developed countries. In this paper, we try to introduce hi-tech MAIT equipment based on corona discharge method.

There's Something in the Air: Empirical Evidence for the Effects of Negative Air Ions (NAI) on Psychophysiological State and Performance

Numerous reports document advances made in our understanding of the effects of negative air ions on physiological functions and human health. Collectively, these reports demonstrate an increasing awareness of their mechanisms, and reflect contrasting findings about their influence. The purpose of the present paper was to review the evidence base for the beneficial effects of negative air ions (NAI) in improving neuropsychological performance and treating mood disorders. Underlying mechanisms, treatments parameters and the extent to which negative air ionization can represent a valuable treatment for affective disturbances are reported together with experimental data gathered from our laboratory. The analysis, particularly with randomized, controlled trials suggests that NAI treatment for mood disorders is in general effective with effects almost equivalent to those in other antidepressant non pharmacotherapy trials. Despite the growth in clinical research, there remained a substantial gap in mental health services to translate state-of-the-art treatments and incorporate them into mainstream practice.

Air ions and mood outcomes: a review and meta-analysis

BackgroundPsychological effects of air ions have been reported for more than 80 years in the media and scientific literature. This study summarizes a qualitative literature review and quantitative meta-analysis, where applicable, that examines the potential effects of exposure to negative and positive air ions on psychological measures of mood and emotional state.MethodsA structured literature review was conducted to identify human experimental studies published through August, 2012. Thirty-three studies (1957–2012) evaluating the effects of air ionization on depression, anxiety, mood states, and subjective feelings of mental well-being in humans were included. Five studies on negative ionization and depression (measured using a structured interview guide) were evaluated by level of exposure intensity (high vs. low) using meta-analysis.ResultsConsistent ionization effects were not observed for anxiety, mood, relaxation/sleep, and personal comfort. In contrast, meta-analysis results showed that negative ionization, overall, was significantly associated with lower depression ratings, with a stronger association observed at high levels of negative ion exposure (mean summary effect and 95% confidence interval (CI) following high- and low-density exposure: 14.28 (95% CI: 12.93-15.62) and 7.23 (95% CI: 2.62-11.83), respectively). The response to high-density ionization was observed in patients with seasonal or chronic depression, but an effect of low-density ionization was observed only in patients with seasonal depression. However, no relationship between the duration or frequency of ionization treatment on depression ratings was evident.ConclusionsNo consistent influence of positive or negative air ionization on anxiety, mood, relaxation, sleep, and personal comfort measures was observed. Negative air ionization was associated with lower depression scores particularly at the highest exposure level. Future research is needed to evaluate the biological plausibility of this association.

A Comparative Study on Decomposition of Airborne Microorganisms by Negative Air Ions and Nano-Ag/TiO<sub>2</sub> as Photocatalyst in Medical Nursing Institution

This study focused on the investigation of the effectiveness of nano-plasma negative air ionization (NPNAI) and photocatalytic oxidation with combining nano-Ag/TiO2 as photocatalyst and UV light irradiation to enhance the disinfecting capability of full-scale bacterial restraining equipment in the medical nursing institute. Results show the bacteria removal efficiencies (η) of different methodologies, respectively. In this removal method, the contributions of photocatalytic oxidation (PCO) as nano-Ag/TiO2 (ave. bacterial restraining rate = 73%) were higher than those of NPNAI (ave. bacterial restraining rate = 17%) for the removal of airborne microorganisms. The proposed equipment can disinfect air to restrain bacteria effectively as demonstrated on-site in medical nursing institutions; the results will be valuable references for designing a full-scale commercialized device for large-scale applications in the future.

Contaminant particles removal by negative air ionic cleaner in industrial minienvironment for IC manufacturing processes

This study was carried out in a closed test chamber under natural decay, negative ionic air cleaner application, as well as air mixing mechanism with negative ionic air cleaner. Among three operation modes, the air mixing mechanism with negative ionic air cleaner can reduce particles better under the flow field condition. In the air mixing, especially vigorous one (5 ACH (Air Changes per hour)), enhanced the air cleaning effect. The highest removal efficiency was measured at a height of 0.6 m from the floor and it was decreased substantially with an increase in height. The relative effectiveness of negative ionic air cleaners was predicted to decrease with an increasing particle size. We also found that there was a limited horizontal diffusion of ions. The empirical curves fit based for the concentration gradient of NAI (Negative air ionization) generated was developed for estimating the NAI concentration with different heights and distances from the source of negative ionic air cleaner discharge.