Healthy Buildings 2017 Europe July 2-5, 2017, Lublin, Poland

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1 Healthy Buildings 2017 Europe July 2-5, 2017, Lublin, Poland Paper ID 0128 ISBN: A Study on Effective Control of Influenza Infection Considering Energy Saving in Buildings Motoya Hayashi 1,*, Kenichi Kobayashi 1, Michiko Bando 1, Hoon Kim 1, Noriko Kaihara 1, Haruki Osawa 1 1 National Institute of Public Health, Wako, Japan * Hayashi.m.aa@niph.go.jp SUMMARY Influenza air-borne infection depends basically on indoor humidity and ventilation rate. The authors proposed an index of influenza infection according to these factors, using the results of the experiments on survival rates of influenza viruses in air by G.J.Harper. This index is a ratio of indoor influenza concentration toward the generation rate of influenza viruses from a carrier in a space. The estimate made using this index showed that if the indoor absolute humidity is higher than a critical point, the required ventilation rate is low and the energy consumption for ventilation and humidification is also low. The indoor air environments of specific buildings were estimated using the data of inspections by health centres in Tokyo. The results were as follows. Although humidity is very low in the buildings, the index is low and the risk of infection is low. The reason is that the ventilation rate a person is very high. A case study on the optimization of ventilation rate and humidity, showed that reducing ventilation rate and retaining higher humidity have a good effect on the control of influenza infection and on energy saving. KEYWORDS emvironment and health of buildings, infection control, air quality, ventilation, energy saving 1 INTRODUCTION The act on the maintenance of sanitation in buildings (AMSB) was established in Japan in The owners of specific buildings are obligated to keep indoor air quality according to the administrative standards for the maintenance of building environments and people s health in buildings as shown in figure 1. However, the ratio of the buildings whose indoor temperature, indoor concentration of carbon dioxide and indoor humidity don t meet the standards, has been getting higher since The ratio of the buildings of a low humidity standard exceeded 60% in One factor of this increase is thought to be energy saving, and the spread of slit-type air conditioning systems is thought to be another factor. Humidity is very low in winter in most buildings. Therefore the risk of virus infection increases in many buildings. The aim of this study is to know the state of ventilation and humidification in order to avoid the risks of air-borne influenza infection considering energy saving in winter.

2 Standards for environment and health management of a building (air environment, water supply and drainage, cleaning, rat and other animals) Health in buildings Obligation Health centre in prefecture or city Inspection Report Guidance Order Owner of building Selection opinion Specific building 〇 entertainment facility, department store,shop, office, etc. >= 3000m 2 〇 school >= 8000m 2 Humidity 40-70RH% Air stream 0.5 m/s Formaldehyde 0.1 mg/m 3 Floating dusts 0.15 mg/m 3 CO 10 ppm CO ppm Temperature deg-c Engineer (building environment and health management) Supervise Building maintenance business cleaning, Management of air environment, cleaning of ducts for air adjustment, drinking water quality test, cleaning of drinking water storage tanks, cleaning of drainpipes, prevention of animals, etc. Figure1 system of the act on the maintenance of sanitation in buildings (AMSB1970) 2 METHODS The measurements under the act on the maintenance of sanitation in buildings were made on CO2 concentration, humidity and temperature etc. However, the measurements of ventilation rate and humidification rate were not made, so it is necessary to predict ventilation and humidity in order to investigate the improvement of indoor air quality in buildings. In the former study, a basic calculation method on ventilation rate and humidification rate was proposed and the misture sources were predicted, and the results showed that indoor absolute humidity depends on not only humidification rate but also ventilation rate a person. Health centres inspect specific buildings and measure their indoor environment. Their data of 2013 in Tokyo were used in this study. Table 2 shows the outline of the buildings. The floor area is from 6000 to m 2 and the number of floors is from 4 to 53. These buildings were constructed from 1961 to The risk of influenza infection through the air depends on ventilation rate and indoor humidity as shown figure 2. G.J.Harper showed the influence of temperature and relative humidity upon the survival rate of viruses in chambers. Jeffry Sharman et al. showed that the survival rate of influenza viruses in the air depends on absolute humidity. Table 2 outline of investigated specific buildings in Tokyo (averages) Number of buildings Floor area m 2 26,000 21,000 48,636 56,800 Number of floors Construction year :entertainment space Exhausted virus Influenza virus Inactivation Humidification Active virus Figure 2 mechanism of air-borne influenza infection in a space

3 G.J.Harper showed the decrease of the survival rate of influenza viruses in the air. The survival rates decrese first in the case of high absolute humidity. The correlation coefficients between the approximation lines of survival rate and the measured date by G.J.Harper are high (R 2 = ). The exponent β of the approximation line depends on absolute humidity(r 2 = 0.84). β = 142 e xi (1) where, xi: indoor absolute humidity (g/kg ) When the generation rate of influenza viruses is 0 after t = 0, the indoor concentration of influenza viruses C inf (n/m 3 ) is shown as the next equation (2). C inf (n/m 3 ) is the number of influenza viruses in the air of 1m 3. Cinf (t) = Cinf (0) e β t (2) This equation shows that the exponent β coresponds to ventilation time. Therefore, the concentration of influenza viruses is calculated using the next equation (3) considering the effect of ventilation and absolute humidity. Cinf = Minf / (N+β) (3) Where, Minf: genaration rate of influenza viruses in the air of 1 m 3 (n/(m 3 h)), N: ventilation time (1/h) When the generation rate of influenza viruses from a person Minf p is used, the next equation is given. Cinf = Minf p / (Qp+βVp) (4) Where,Qp: ventilation rate a person (m 3 /hp), Vp: space volume a person (m 3 /p) The ratio of the concentration of influenza viruses to the generation rate of influenza viruses from a person Γ is shown as the next equation. The ratio is thought to be an index of influenza infection control. Γ = Cinf / Minf p = 1/ (Qp+βVp) (5) The index of influenza infection control Γ is 27 when indoor temperature is 24 deg-c and the indoor relative humidity is 40 RH%. The index of influenza infection control Γ is 31 when indoor temperature is 17 deg-c (AMSB1970) and the indoor relative humidity is 40 RH% (AMSB1970). The ventilation rate a person Qp is calculated using the next equation. Qp = M_CO2 p/d_co2 (6) Where, D_CO2: the difference of the indoor conentration and the outdoor concentrations of CO2, M_CO2 p: the ganeration rate of CO2 from a person The energy loads for ventilation and humidification a person Lvhp are calculated using the next equation. Lvhp = ( kt D_t + kx D_x ) Qp (7) Where, kt: coefficient of ventilation (=0.34), kx: coefficient of humidification (=0.834), D_t: the difference of indoor temperature and outdoor temperature, D_x: the difference of the indoor absolute humidity and outdoor absolute humidity

4 3 RESULTS Figure 3 shows the relationship between the index of influenza infection Γ and energy load Lvhp. When Γx10 2 is 2.7 (24 40RH%) and Qp is 30 m 3 /hp, the absolute humidity is 7.2 g/kg, and Lvhp is 0.35 kw/p. In order to make Γ lower, Qp and/or Xi should be higher. These strategies increase Lvhp. When Qp decreases from 30 m 3 /hp to 20 m 3 /hp and Xi increase from 7.2 g/kg to 9.4g/kg, Γx10 2 keeps 2.7, and Lvhp decreases from 0.35 kw/p to 0.27 kw/p. It shows the feasibility of energy saving in consideration of influenza air-borne infection risks. Figure 4 shows the measurement results. Indoor temperatures are almost adequate. However indoor humidity is very low. CO2 concentrations are lower than 1000ppm (AMSB1970). In the case of school, CO2 concentration is set to be 1500 ppm according to a standard for school environmental sanitation, and the required ventilation rate a person is estimated to be almost 11 m 3 /hp. Therefore it is certain that the measurements were carried out when there were very few people. Indoor absolute humidity Xi (g/kg') Γ(Qp=40) Γ(Qp=50) Γ(Qp=60) Γ(Qp=20) Γ(Qp=30) Index of influenza infection Γ = 1/ (Q p +βv p ) β = 142 e xi Energy load of ventilation and humidification L vhp =(k t D _t +k x D _x )Q p k t =0.34,k x = Index of Influenza infection Γx10^2 Lvh(Qp=20) Outdoor absolute humidity: 3 g/kg' Outdoor temperature: 0 deg-c Indoor temperature 24 deg-c Lvh(Qp=30) Lvh(Qp=40) Lvh(Qp=50) Lvh(Qp=60) Energy load of ventilation and humidification a person L vhp (kw/p) Figure 3 relationships between absolute humidity and ventilation rates a person Qp / energy loads of ventilation and humidification a person Lvhp Indoor absolute humidity Xi (g/kg') Temperature (deg-c) Relative humidity (RH%) Absolute humidity (g/kg') CO2 concentration (ppm) 1, Figure 4 inspection results on temperatures, humidity and CO2 concentrations

5 Figure 5 shows analysis results. Qp is higher than a required ventilation rate a person (11 m 3 /hp in school, 30 m 3 /hp in the other buildings) (5-1). In this situation, indoor humidity is very low, because the amount of moisture from humans is little and humidification is not enough (5-2). Capacity in 5-3 is a calculated result on condition that the space is filled to capacity and the CO2 concentration meets a standard value (1500ppm in school, 1000ppm in the other buildings) (5-3). Lvhp at the inspection is 0.35 to 0.6, and it is higher than Lvhp at Capacity (5-3). It also shows that the measurements were carried out when there were very few people in the buildings, so Γat the inspection is lower than at Capacity. Figure 6 shows the results of the studies on optimizing CO2 concentration and relative humidity. When the relative humidity is set to be 40RH%, Γdoes not change and Lvhp increases. When the CO2 concentration is set to be 1000ppm, Γincreases very much and Lvhp decreases very much. Even if relative humidity is set to be 40RH% additionally, the results are almost the same. When relative humidity is set to be 50RH% and CO2 concentration is set to be 700ppm, Γx10^2 is 1.4 to 1.8 and Lvhp is 0.25 to 0.4. These case studies show that the optimization of humidity and ventilation rate is effective for both of the control of influenza air-borne infection and energy saving. Qp (m 3 /hp) H2O(g/kg') Humidifi cation Human Outdoor air Energy load of ventilation and humidification a person: L vhp Capacity Inspection Index of Influenza infection: Γx10^ Figure 5 analysis results of ventilation rate a person, moisture sources, and influenza airborne infection and energy load Energy load of ventilation and humidification: Lvh(kW/p) RH%700ppm 40RH%1000ppm 1000ppm 40RH% Inspection Index of Influenza infection: Γx10^2 Figure 6 index of influenza infection and energy load of ventilation and humidification

6 4 DISCUSSION In order to control influenza air-borne infection in buildings, an index was proposed based on the experimental results by G.J Harper. The characteristics of infection has to be investigated and new knowledge may change the optimization results on ventilation and humidification. The influenza infection risks were estimated using the data of inspections by health centres in Tokyo. Because the data are obtained during the inspections, the measured air environments may not be similar to the usual air environments. In order to control indoor air environment, it is necessary to propose an effective inspection method using a proper estimation of influenza infection. 5 CONCLUSIONS This study shows a feasibility of the optimization of ventilation and humidification to control influenza air-borne infection and energy consumption. Ventilation rate and humidity have to be optimised considering not only these factors but also indoor air pollution, vapour condensation and other factors. When the ventilation rate is kept a minimum and humidity is high, it is necessary to improve insulation to prevent vapour condensation especially at windows. 6 ACKNOWLEDGEMENTS This study was financially supported by a Grant-in-Aid for Health and Labour Sciences Research Grant (H26-health/crisis-007) provided by the Japanese Ministry of Health, Labour and Welfare. The authors express their gratitude to the members of the committee on studies on inspection and guidance about environmental health in buildings. 7 REFERENCES Hoon Kim, Motoya Hayashi, Noriko Kaihara, Haruki Osawa and Michiko Bando Measurement of temperature, humidity and CO2 concentration and estimation on humidity control in facilities for the elderly in winter. Indoor Environment Vol18.No Environment and Health Management of Buildings -Law for Environment Health in Buildingnotification and commentary Japan Architectural Health, Management and Education Center. Azuma K, Ikeda K, Kagi N, Yanagi U, Osawa H. Prevalence and risk factors associated with nonspecific building-related symptoms in office employees in Japan: relationships between work environment, Indoor Air Quality, and occupational stress. Indoor Air Sep 22. DOI: /ina [Epub] G.J.Harper, Airborne micro-organism: Survival tests with four virus J.Hyg; , Thomas P. Weber, Nikolaos I. Stilianakis, Inactivation of influenza A viruses in the environment and modes of transmission: A critical review, Journal of infection , 2008 Jeffrey Sharman, Melvin Kohn; Absolute humidity modulates influenza survival, transmission, and seasonality PNAS vol.106 no9; , March Hoon Kim, Motoya Hayashi, Noriko Kaihara, Haruki Osawa, Michiko Bando, Measurement of temperature, humidity and CO2 concentration and estimation on humidity control in facilities for the elderly in winter, Indoor Environment, Vol18,No2.pp77-87, 2015