Contamination-free conditions provided by cleanrooms are essential for modern industry to ensure their products are not contaminated during manufacturing, and will malfunction. Cleanrooms are used in the manufacture of a variety of electronic and mechanical devices essential for computers, cars, aeroplanes, spacecraft, televisions, etc. They are also used in the manufacture of medicines, medical devices, and food, to ensure that these products are not contaminated with microbes that cause infections in people. Cleanroom technology is divided into three parts, namely, design, testing, and operation, of cleanrooms, and this book discusses these three subjects. The book is mainly intended for people who have recently entered the cleanroom industry, as well as providing information for educational courses. The author has written the book called ‘Cleanroom Technology -Fundamentals of Design Testing and Operation' but there was a need for a simpler and shorter book that contained the most important information about cleanroom technology. This present book is an abbreviated version of the previous book, and one quarter the size.