The International Standards Organization (ISO) is responsible for the latest classifications for clean room environments. These global standards, which have more classes than previous United States systems, are carefully judged, since the slightest error can often affect the sensitive materials that must stay in them. Because of this, you can only get cleanroom certification if you meet the standards in several categories. Here we have a brief explanation of the major categories in this process so that you can learn a bit about the subject before diving into your own classification process.
The first part of clean room classification is to measure the number of particles you can find per micrometer. It ranges widely, and the fewer particles found, the higher the possible ISO classification. It’s important to note that the number of particles at any given time varies with the number of people in the room and the activity level. If you bring in people and equipment, no matter how thorough you are in the decontamination process, are very likely to bring in extra particulates with them.
You don’t want contaminated air rushing into the clean room every time you open the door, so it’s important to make sure your clean room maintains positive pressure. Most people use air locks to accomplish this.
To meet proper air flow standards, you need to address three factors: air change rate (ACR), ceiling fan coverage, and air flow velocity. These are all combined in a single chart where all factors must be satisfactory for a certain type of clean room certification. For instance, an ISO 8 only must replace the room’s air with filtered outdoor air 5-48 times per hour while ISO 1 requires 360-600 changes per hour. ISO 8 needs 5-15% ceiling fan coverage while ISO 1 needs 80-100%, despite the immense power these fans use. As for the ventilation efficiency, ISO 8 needs the air moving at 1-8 feet per minute while ISO 1 needs it moving at 600-100 feet per minute.