Clean Room

When analyzing trace element abundances and isotope compositions in extraterrestrial materials, sample preparation must be performed in a clean environment to minimize the contamination from terrestrial materials. Cleanroom is a facility that supplies air from which particles have been removed by filtration with an air filter to control airborne particulates in the room. HEPA filter, which can retain 99.97% particles that are 0.3 μm or larger, is commonly used for making clean air for cleanroom.

Each cleanroom has an index of cleanliness that is quantified by the number and size of particles permitted per volume of air. For example, Class 100 and Class 1000 defined by the US federal standard denote 100 and 1000 particles of size >0.5 μm are permitted per ft^3 of air, respectively. Cleanroom is always kept at a positive pressure (a pressure higher than the outside), and the inflow of dust from the outside can be suppressed. Our cleanroom consists of three sections: changing room, clean section, and the cleanest section. The airflow comes from the cleanest section toward the changing room in order to effectively scavenge the particles in the cleanroom. The cleanliness of the cleanest section is better than Class 1000. In the cleanest section, there are 10 working stations in which chemical treatment for meteorites samples is performed. The cleanliness of the working stations, each of which is equipped with a small HEPA filter, is better than Class 100.