There are numerous fungi in the house environments. These fungi are generally originated from soil. After floating the fungal cells such as spores and hyphae in air, they attached on the surface of dwelling house. If the conditions in indoor environments are suited to fungi, the fungal contamination is apparently progress so soon. Among the fungi, Cladosporium are most predominant species that specially detects from air, contaminated materials and the dampness environments. This mold is easily scattering around the indoor environments under wetty conditions. Therefore, in case of dampness in dwelling house, it should pay attention to the moisture conditions.
Most of fungi such as Cladosporium, Alternaria and Mucorales are inactive less than Aw 0.90, Aspergillus and Penicillium are less than Aw 0.80 and also xerophilic fungi such as Eurotium are less than Aw 0.65. In this paper, the fungal ecology and biology in indoor environments are introduced in detail.

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House dust mites are well-known as the most important major allergen that causes allergic diseases such as bronchial asthma and allergic rhinitis in the indoor environment. Fungi are known as indoor allergens that cause IgE-mediated allergic diseases such as bronchial asthma, allergic rhinitis, atopic dermatitis as well as IgG-mediated and/or cell-mediated allergic diseases such as allergic bronchopulmonary aspergillosis (ABPA) and hypersensitivity pneumonitis. However, details about the mechanisms of action and analyses of allergens in fungal allergies have not been as fully examined as in mite allergies. Candida albicans and Malassezia, which are normal flora in the human body, and Alternaria, Cladosporium, Aspergillus, and Penicillium, which are frequently identified as outdoor fungi, are important fungal allergens. Allergen extracts of those fungi have been widely used for skin tests and detection of IgE antibodies in sera for diagnosis of causative allergens. Recently, the roles of the xerophilic fungi Aspergillus restrictus and Eurotium, which prefer dry environments such as house dust on the floor to wet conditions such as in the bath room, have been attracting attention as causative allergens of allergic diseases in the indoor environment. More studies are needed to elucidate the importance of those fungal allergens.

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There were few reports on the collection efficiency of the airborne bacteria sampler using biological particles in a laboratory.
We studied collection efficiency on the 5 kinds of samplers for biological particles using the test chamber atomized microorganisms and proved the slit sampler (casella) of the impaction type show surpassing collection efficiency in 1970. However, as the study was qualitative, we have developed the skillful method and designed the test equipment for collection efficiency using biological particles of the samplers and performed a quantitative experiment. (1993) As the results of these experiments, the collection efficiency of samplers indicates the significant difference and the collection efficiency of the portable type samplers indicates lower than that of the fixed type samplers.
Nakata et al. developed the portable sampler which has as high collection performance as fixed type samplers examined by the above quantitative method. (1999)
Here, we introduce these results.

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Air filters are used for reducing indoor air contamination caused by suspended particulate matter in non-occupational environments. Recently, as the concerns have being gathered for the problem of the indoor air pollution by viable particles, air filters are expected not only in removal of suspended particles but airborne microbes. There are various kinds of air filters and the evaluation method of the filtration efficiency is according to the purposes.
In this paper, firstly, filtration mechanisms of an air filter, i.e., inertial impaction, interception, diffusion, and electrostatic attraction, were described. Secondly, the JIS (Japanese Industry Standard) method and ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) method for evaluating an air filter were introduced. Regarding the JIS B 9908-2001, air filters are classified by 3 types according to the object particle size, and the filtration efficiency of these 3 types are evaluated by particle size method, dust spot method, and weight method, respectively. About ASHRAE 52.2, the filtration efficiency is evaluated only by particle size method. Finally, the in situ experimental results about the filtration efficiency of low- and medium-efficiency particulate air filter over both suspended particles and airborne microbes under real operating conditions were reported. Results show that there are significant correlations of filtration efficiency between airborne microbes and distributed suspended particles. Each of the filtration efficiency over airborne Staphylococcus aureus, bacteria, and fungal spores is almost equal to the filtration efficiency over suspended particulates larger than 1 μm, 2 μm, and 5 μm in diameter, respectively.

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It has been reported during the past decades that allergic diseases including bronchial asthma, allergic rhinitis, and atopic dermatitis have been increasingly prevailing especially in developed countries. The clear reason is still poorly understood, but it has often been assumed that the drastic alteration of modern architecture technologies such as airtight and insulating structure of housing has allowed mites and molds to inhabit and propagate not only at the limited season of high temperature and humidity favorable to these organisms, but all the year around. Dust mites are most likely to have the allergens that induce the allergic diseases. Clean hygienic environment of modern housing seems also to contribute to the recent prevalence of allergic diseases due to the reduction of “hygiene hypothesis”.
Influenced by lots of findings suggesting that dust mite allergens are the most responsible to the allergic induction, house inhabitants have been trying to eliminate the dust mites from the indoor environment not only with use of vacuum cleaner but also other modern methods. This review attempts to overview the current activities in Japan for the elimination of indoor mites by means of modern technologies including active ions, polyphenol, enzyme, and high-density cloth.

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A description is given on mites and small insects, which damage health and cause discomfort in indoor environment. For indoor-environmental studies, mites and small insects are classified into the following three types: “indoor space outbreak type” coming from infested construction materials and ventilation ducts,“outdoor outbreak invasion type” brought indoor from affected plants in the garden and verandah, and “article adhesion invasion type” carried in with furniture and goods from outside. Another classification, by ecology and the pattern of damage to humans, divides them into sanitary insect pest, house-hold insect pest, food stuff insect pest, clothing harmful insect pest, and nuisance, among others.
This paper discusses the morphological and ecological characteristics of 12 kinds of mites [American house dust mite (Dermatophagoides farinae) et al.] and 19 kinds of insects [cigarette beetle (Lasioderma serricorne) et al.] that typically infest indoor environment.

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The preliminary experiments were tried to obtain the basic data for determination of the air-cleaner evaluation method on removability of airborne microbes. An examination room for spray of living microorganisms was prepared, the spores of Wallemia sebi and Penicillium frequentans were prepared for the spray, a nebulizer method and an ultrasound method were adopted for spray of the spores, and gelatin filters were used for sampling of the scattered spores in the air of the examination room. Both nebulizer method and the ultrasound method were applicable for spray of spores. The preliminary evaluation tests on removability of airborne microbes were tried on a commercially available air cleaner. Although the decreasing effect of airborne microbes with the filter was detected, the decreasing effect was not detected with the emission of cluster ions at the air cleaner.

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