Estimation on humidification and ventilation for infection control in residence for the elderly

Purpose / Context - The aim of this study is to clarify an estimation method of humidification for infection control in residences. In Japan indoor humidity is very low in winter especially in recent insulated houses without unvented stoves. Dwellers know that it is necessary to keep humidity ade-quate for infection control, but most of them don’t know the moderate humidity or the effect of venti-lation for infection control. In this study, the state of influenza infection control was evaluated using the measurement results on indoor air in the rooms of six Japanese facilities for the elderly. The temperature is kept better in these residences than that in common Japanese houses. But the humid-ity is quite very low in winter. The energy saving is thought to be one of the causes of this state. Methodology / Approach - Under the assumption that influenza virus generate at a constant rate, the concentrations of survived influenza viruses in indoor air were calculated using an equation, which is given on the basis of the survival tests on influenza virus by G.J.Harper. The equation gives the concentration of influenza viruses using the ventilation rates and absolute humidity. Then an index on virus reduction which integrates ventilation effect and humidity effect was proposed. Results - The energy consumption of ventilation and humidification for infection control is calculated using this index. The results show that it is effective to control ventilation rate for both of infection control and saving energy in many rooms in these facilities. Key Findings / Implications - Effective strategies for infection control in residences are discussed using the index of influenza infection control. Originality - The index of influenza infection control is proposed in this study. This index is useful to estimate indoor air quality. The index is expected to be used for the design of building performances and air conditioning systems.