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JACA (Japan Air Cleaning Association)

The Abstracts of the paper carried by the Journal of JACA

vol.57-5(2020/1/31)

Background determinants for building sanitation management standards and the recent scientific knowledge

The Law for Maintenance of Sanitation in Buildings was enacted in 1970 in Japan. The Building Sanitation Management Standards was also established as the decree of the Ministry of Health and Welfare, which specified management standards for control of indoor air quality (IAQ), management of water supply and sewage, cleaning and the control of rodents and insects. This law is applied to specially designed buildings such as offices, stores, hotels, entertainment facilities, assembly halls, libraries and museums, whose total floor areas exceed 3,000m2 and schools exceed 8,000m2 in Japan. The standards for IAQ regulate seven items, i.e., indoor air concentration of carbon dioxide, carbon monoxide, suspended particles, formaldehyde, and temperature, relative humidity and air flow. An increasing variety of new buildings have been designed because of requirements for energy saving, higher convenience or comfort. Thus, regular maintenance and management for the sanitary environment has been more important for the buildings. And then, the appropriate maintenance and management for each intended use building might be needed. Fifty years has been elapsed since establishment of the Building Sanitation Management Standards. In this article, background determinants for building sanitation management standards have been reported. In addition, the recent scientific knowledge for seven items of the standards have been reviewed.

State of nonconformity rates on indoor air environments in specific buildings

The nonconformity rates of humidity, temperature and carbon dioxide concentration have increased with the number of specific buildings since 1999. And reports made by the owners of specific buildings are substituted for inspections by government officials in most prefectures. One of the factors in the increase of nonconformity rates of temperature, humidity and carbon dioxide concentration is the increase of reports using measurement data by building maintenance suppliers. The frequency distribution of the differences between indoor concentration and outdoor concentration in Tokyo follows Weibull frequency distribution. The increase of ambient concentration is thought to increase the indoor concentrations in specific buildings. The nonconformity rates of carbon dioxide concentration depend on not only ambient concentration but also the rates of ventilation reduction and survey methods by governments. The nonconformity rates were calculated using an equation composed on the basis of Weibull frequency. The coefficients of these factors were calculated using the equation and the survey data on all Japan. The increase of ambient concentration made the nonconformity rate of indoor concentration 3.1% higher and ventilation reduction made it 7.2% higher and the change of survey method made it 11.6% higher in these nineteen years.

Indoor environment of working spaces in each scale of office buildings

In order to clarify indoor environment of working spaces in small, medium scale and specified buildings, the questionnaire survey was conducted among approximately 170 office buildings during the winter and summer of 2018. The number of medium scale buildings, which need not to meet to ‘Law for Maintenance of Sanitation in Buildings’, was estimated to be half of specified buildings through statistical data provided by ‘Ministry of Land, Infrastructure, Transport and Tourism’. This investigation aims to provide the outcomes for discussion whether to extend the range of specified buildings. Office workers in medium scale buildings tended to complain the occurrence of static electricity and perception of moldy odor during winter in comparison with office workers working in specified buildings. And during summer, more office workers in medium scale buildings complained feeling indoor dampness, perception of moldy odor and unpleasant smell than in specified buildings. These indoor problems in working spaces of office buildings were related to indoor humidity and it seems to reflect the building characteristics of medium scale buildings which are not enough to keep indoor humidity adequate without the equipment for indoor humidity control. In addition, female office workers have dissatisfaction for indoor environment in working spaces.

Current status of indoor temperature and humidity in specific buildings

Although diversification and sophistication of monitoring technology based on the Law for Environmental Health in Buildings is required due to the complex use of buildings and changes in building facilities, the proportion of buildings which do not conform to building environmental health management standards (non-conformity rate) for specific buildings is increasing. Among others, relative humidity tends to be low and non-conforming in winter, and it has been pointed out that this may be because humidification is being reduced as a means of saving energy. In this report, we are going to give examples of the indoor thermal environment using on-site inspection data for specific buildings in Tokyo. In addition, we present survey results for office buildings as examples of the indoor thermal environment of buildings equipped with a vaporizing humidifier and individual air-conditioning systems, which is a trend in recent building equipment.

Carbon dioxide concentration in specific buildings

The mean nonconformity rates of SPM (suspended particulate matter), CO and airflow velocity have been low, while those of CO2, air temperature and relative humidity have demonstrated an increasing trend year by year. In particular, the nonconformity rates have increased rapidly after the Great East Japan Earthquake (2011), and the year after the revision of energy saving law (1999) and the Law of Environment and Health in Building (2002). It leaded to the deterioration of indoor air temperature and humidity, and also the reduction of ventilation (increasing of CO2 concentration).
In today’s society, LEHB is being questioned as to how should control and manage the indoor hygiene environment in line with the increase of large-scale buildings, compounding of usage, and technological advances in building equipment, diversification and sophistication of monitoring technology etc.

Design methods and system selection for industrial clean room

Japanese production facilities in the manufacturing sector not only demand maintenance of quality but also a reduction in production costs. In large-scale clean rooms in particular, the demand for energy conservation measures is high, as the standard energy consumption of these types of facilities is enormous. A large amount of conveyance power is required to maintain the interior temperature, humidity, and cleanliness standards in clean rooms because large volumes of clean air must be continuously circulated through a high-performance filter. As a first step toward the reduction of this conveyance power, we explain the relationship between the air circulation process and the interior conditions. Understanding this relationship is key to reducing the conveyance power required. Furthermore, we propose the use fo our company’s unique technology, a Swirling Induction Type HVAC system (TCR-SWIT) that can efficiently manage the air conditioning and cleanliness requirements of such large-scale clean rooms. This study also introduces the basic technical descriptions of the TCR-SWIT system.