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Morimoto S.,Shinryo Corporation | Tang H.,Shinryo Corporation | Tanabe S.-I.,Waseda University | Tsutsumi H.,Showa Womens University | Hori S.,Juntendo University
Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate | Year: 2014

If a patient is diagnosed with an airborne infectious disease, medical workers can use airborne precautions and isolate the patient in a negative pressure room. However, if the patient has not been diagnosed with the airborne disease, then the medical workers cannot use precautions due to the unwieldy nature of the N95 respirator as well as Powered Air Purifying Respirators (PAPR) being expensive. Furthermore, the patient may share a 4-bed room with compromised patients. In this study, we discussed the reduction methods of droplet nuclei concentration to reduce the infection risk in 4-bed rooms. We conducted the experiments in a full-scale test room. Air supply diffusers were on the ceiling, a square cone diffuser was in the center and four linear slot diffusers were on the step side of each bed between a wall and a partition wall. The largest drop in concentrations occurred with smaller air volumes for the square cone diffuser and larger air volumes for the linear slot diffusers. The concentrations were reduced further by using a rolling screen.

Morimoto S.,Shinryo Corporation | Hori S.,Juntendo University | Sakimura Y.,Toda Corporation | Ito A.,Akira Ito is with Nikken Sekkei Ltd. | Hiramatsu K.,Juntendo University
IAQ Conference | Year: 2011

The negative pressure room is indispensable for controlling airborne pathogens such as measles virus and Mycobacterium tuberculosis. However, the conventional negative pressure room is usually designed to regulate air change volume and temperature, but no dynamic analysis of distributions of droplet nuclei under the various air conditions has yet been discussed. We analyzed the dynamics of droplet nuclei in the negative pressure room affected by various air directions, using a Computational Fluid Dynamics (CFD) method. The concentrations of droplet nuclei in the room were increased immediately and reached a steady state 30 minutes, after patient entry. The droplets in a patient's breath were estimated to be diluted approximately 1,100 times soon after release. Once patient has been removed from the room, the concentrations of droplet nuclei were dropped to one thousandth by 60 minutes. No reflux to the anteroom was observed unless the inner door was closed. After opening the door, the concentrations in the anteroom and the corridor increased dramatically by the refluxed air. In addition, the ideal alignment of an exhaust and supply which affected the concentrations was assessed under the same air change rate. It was concluded that directional airflow from feet to the head of patients can reduce the concentrations of droplet nuclei better than conventional ventilation. Dynamic analysis of the distribution of droplet nuclei using a CFD method is useful in designing the optimal isolation room for patients with airborne pathogens. © 2011 ASHRAE.

Arai K.,Waseda University | Ogata M.,Waseda University | Fujiwara M.,Waseda University | Tsutsumi H.,Showa Womens University | And 4 more authors.
Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate | Year: 2014

We propose an infection-control bed as an infection-control technique using a push-pull local ventilation system and evaluated this bed in this study. The effectiveness in reducing the risk of airborne infection was evaluated using a cough-simulation machine. The machine releases carbon dioxide (CO2) as a tracer gas. The simulated cough was set up to be released in two directions. The directions were assumed such that they typically pose an infection risk to the doctor. In addition, the diffusion-prevention effect in the hospital room was also studied. When the cough was released directly above the bed, the amount of CO2 gas sampled at the measurement points above the patient decreased. The concentration at the most effective measurement point was 91.1 % lower as compared to that in the control case. When the cough was released directly in the doctor's direction, the concentration at the doctor's respiratory area was 56.7 % lower as compared to that in the control case.

Ogata M.,Waseda University | Suzuki M.,Waseda University | Tanabe S.-I.,Waseda University | Hori S.,Juntendo University | And 2 more authors.
Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate | Year: 2014

The objective of this research is to investigate the relationship between the size of a multibed patient room and the risk of airborne infection. Computational fluid dynamics simulations were used to address a number of room sizes with two types of ventilation systems. Assuming that one patient was infected and that infectious agents were contained in exhaled air, the risk of airborne infection was evaluated by the respirable concentration of each patient and the concentration distribution. The results of the simulations show that the airborne infection risk reduced with an increase in the room area, and that the risk of airborne infection tended to increase when the distance between the source of infectious agents and the exhaust outlet was larger than 2.3 m under personal ventilation conditions. In ceiling cassette type conditions, an increase in the room area may increase the risk of airborne infection because the decline in ventilation efficiency and the increase in the ventilation rate decrease the risk of airborne infection.

Fukada K.,Shinryo Corporation | Sakai K.,Meiji University | Ono H.,Environmental Science Research Laboratory
14th International Conference of IBPSA - Building Simulation 2015, BS 2015, Conference Proceedings | Year: 2015

In this paper, we compared measurement results with the CFD analysis results using several of modeling methods for a four-way cassette type outlet. As a result, we compiled possible phenomenon in the case of inappropriate modeling methods. For example, the influence of the Coanda effect was overestimated than measurement results when we placed the outlet to the height that was the same as a ceiling and set diagonal airflow condition. Finally we described a modeling method of CFD parts which is appropriate for business and the design phase even if we carry out CFD analysis using a coarse mesh.

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