This air supply must be accounted for in the cleanroom HVAC calculations. The equipment in the room, along with the product manufacturing, generate dust that must be removed with the correct amount of air.Ĥ) The fume hood or biosafety cabinet (BSC)Ī fume hood or laminar flow cabinet needs constant air supply-just like the cleanroom. The heat gain produced by the equipment inside the cleanroom is used to determine the cooling required. Similar to people, equipment generates heat and dust. Therefore, it is important to maintain a comfortable environment, usually between 66.5☏ and 70☏ (19☌ and 21☌). People in the cleanroom usually wear coveralls to limit contamination. The number of operators is also used to calculate the level of conditioning to compensate for the heat that they produce. People generate airborne contaminants, but also heat. The more people working in the cleanroom, the more airflow is needed to get rid of the contaminants. When designing the HVAC system, the number of people working in the room at the same time must be taken into account. Airborne particles, such as skin flakes, cosmetics, perfume, spittle, clothing debris (lint, fibers) and hair, are the usual suspects. People are responsible for most of the particles generated in a cleanroom. The airborne contamination level of a cleanroom depends largely upon the activities in the room and the personnel. You can see the difference by comparing the airflow in the calculator using the same inputs but varying the size of the room or the height of the ceiling.Ģ) The number of people working in the room People often forget that the height of the room directly impacts the CFM (airflow). One way to save on costs is to lower the ceiling. The width, length, and height of the classified rooms and their layout must be used for HVAC calculations. The bigger the room, the more air you need. The volume of air in the cleanroom will influence the amount of airflow needed. The use of a fume hood or biosafety cabinet (air extraction).The number of people working in the room.Below are some other elements that influence the required airflow. But operations occur in cleanrooms and must be accounted for in the HVAC calculation. It is easy to make a room clean if no one is inside, with no equipment, and no material movement. What influences cleanroom HVAC engineering? The air changes per hour and CFM must be calculated by an HVAC engineer based on experience and understanding of the particle-generating potential of the process. If there is a significant generation of particles in the process, the higher number in the range is selected. At Mecart, using our cleanroom airflow calculator, we assumed 10 to 30 air changes per hour (ACH) for an ISO 8 30 to 65 ACH for an ISO 7 80 to 150 ACH for an ISO 6 200 to 450 ACH for an ISO 5. Various recommendations for air change ranges can be found on the Internet. A cleanroom with activities that generate few particles versus one that generates a lot of airborne particles, even if both ISO 7, will not require the same air changes per hour. Notice that the term “range” is used-not “value”. The ISO cleanliness level (ISO 8, ISO 7, ISO 6 and ISO 5) however gives a hint on the ACH range required. The concentration of particles of ≥0.5 µm should be below 352,000 particles of ≥1 micron should be below 83,200 and particles of ≥5 microns should be below 2,930. For example, for ISO 7, particles smaller than 0.5 microns (≥0.1 µm, ≥0.2 µm, ≥0.3 µm) are not taken into consideration. ISO 14644-1:2015 can only tell you the result that you must aim for: the maximum concentration limits for particles. Air changes per hour is the number of total replacements of a room’s air in one hour. ISO 14644-1:2015 does not specify the air changes per hour (ACH) for each cleanroom class because it depends on many factors. However, classification alone isn’t sufficient for calculating the airflow. This means that the HVAC system must be capable of conditioning more than double the air. The amount of air is different in an ISO 6 and ISO 8 cleanroom. ISO classification doesn’t dictate airflow It takes a mix of engineering skills, understanding the particle-generating potential of the process, and experience. Cleanroom HVAC engineering is not an easy thing. We get a lot of questions about HVAC calculations and the airflow requirements of a cleanroom.
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