Abstract
In general, the Japanese spend some eighty percent of their day working in thermally-insulated, air-tight residential or office buildings. Lack of proper ventilation in these buildings give rise to a number of problems including concentration of hazardous chemical substances emitted from building materials and open type heaters, and a rise in room humidity and condensation. Furthermore, lack of proper ventilation promotes increased growth of room bio-pollutants (allergens), such as mites, mold and house dust, and studies of allergic diseases traceable to these substances have shown a marked tendency to increase over the years. Currently, one-third of all Japanese suffer from some form of allergic diseases, while about one-tenth are hypersensitive to chemical substances.
Now believed to be responsible for anaphylaxis to chemical substances, concentrations of formaldehyde (HCHO) and volatile organic compounds (VOCs) given off by interior finishing materials and furniture is very low in residential spaces. To accurately measure these concentrations, it is necessary to concentrate the air sample during sampling and to employ high-precision analyzers such as a gas chromatographic (GC) analyzer to obtain the results. Since these complicated sampling and analytical operations require a high-level of expertise, the development of an on-the-spot precise measuring instrument has long been awaited. This study examines the application of three semiconductor-based odor sensors each capable of measuring and evaluating HCHO and VOCs levels in low concentrations quickly and in a timed sequence. HCHO and VOCs in a variety of concentrations were measured both in the field and in a special laboratory chamber. To evaluate the characteristics of each sensors, the results of the measurements were compared with resultsobtained from high-precision analyzers, such as a GC Analyzer, a Gas Chromatography Mass Spectrometer and a Liquid Chromatographic Analyzer. A relatively good correlation was obtained between the results, indicating the sensors can be used to develop an effective complementary system to enhance the analyzers. Furthermore, the effects of moisture and chemicals which could interfere with the proper operation of the sensors were studied under various conditions to clarify the characteristics of the interference.
In conclusion, this study proposes some the essential technology required to accurately and quickly measure HCHO and VOCs levels in low concentrations in residential spaces.
