Scholars Journal of Engineering and Technology (SJET) ISSN 2321-435X (Online) Sch. J. Eng. Tech., 2014; 2(1):45-49 ISSN 2347-9523 (Print) ©Scholars Academic and Scientific Publisher (An International Publisher for Academic and Scientific Resources) www.saspublisher.com 45 Research Article Comparison of Hepa Filter Testing and Standard Particle Measurement in Clean Rooms Mana Sezdi Dept. of Biomedical Device Technology, Istanbul University, 34320, Istanbul, Turkey *Corresponding author Mana Sezdi Email: Abstract: The high quality air without particle must be provided in operating rooms that are known as clean room. Particles cause the risk of infection in clean rooms. But, the infection risk ratio decreases by using a clean-air system. For a perfect clean room, the clean-air system must be controlled by measuring particles and must be classified in according to the international standard. The related standard is, ISO 14644-1:1999(E) Cleanrooms and associated controlled environments Part 1: Classification of air cleanliness. In according to the standard, the clean room is classified from ISO Class 9 to Class 1 by measuring of particles (0,1μm, 0,2μm, 0,3μm, 0,5μm, 1μm, 5μm). The clean room classification requires a scientific study. But, sometimes, the particle measurement, unfortunately, is performed by non-licensed personnel by only controlling of hepa filters instead of standard methods. In this case, the clean room can not be classified. The objective of this study, is to show the difference between the scientific measurement and the random measurement of particles, and resultly, to consider the unwanted results of the hepa filter testing. In this study, the particle measurements of an operation room were performed by controlling of hepa filters and by applying international standards, respectively. Thus, the results of two measurements were compared. This study announces that the nonstandard measurements that are performed by personnel without license, may cause to report a bad operation room as a good classified room. The subject needs the standardization and the biomedical professionality. Keywords: clean-air system, hepa filter, laminar flow, particle, clean room INTRODUCTION A clean room is an environment that has low level of environmental pollutants such as dust and particles. In other words, a clean room has a controlled level of particle number per cubic meter at a specified particle size. By filtering and cleaning the air, it is possible to circulate the air of 80% without any contamination. Generally, the filters used for air filtration of clean room, are HEPA (High Efficiency Particulate Air) filters. HEPA filters remove the 99.97% of the particles (0.3μm or bigger) [1]. In clean-air systems, according to the DIN standards, the particles are removed by using the filters with 3 steps. All particles and oil-water aerosols are catched in the first filter. The second filter that is the coal filter, sucks up all oil vapor and smell. All microorganisms are filtered in third and the last bacterial filters [2]. Controlling of clean room is performed by using the method of “the clean room classification”. The classification of the clean room is determined by the international standard of particle measurements. The related standard is, ISO 14644-1:1999(E) Cleanrooms and associated controlled environments Part 1: Classification of air cleanliness [3]. The main criteria for the classification of clean rooms is particle size (0,1μm, 0,2μm, 0,3μm, 0,5μm, 1μm and 5μm) and particle concentration [4]. In addition to them, there are many technical points that must be considered during particle measurement. These are;  number of measurement points,  location of measurement points,  measurement repetition,  sample volume,  sampling time and  flow rate and sensitivity of the used particle counter. In according to the ISO 14644-1 standardization, the maximum permitted concentration of particles for each considered particle size is determined from the following equation [3]: C n = 10 N x (0,1 / D) 2,08 where C n is the maximum permitted concentration (particles/m 3 of air) N is the ISO classification number, which shall not exceed a value of 9. D is the considered particle size, in micrometers. 0,1 is a constant.