To determine the cleanliness of your critical environment, you will first need to identify which clean room classification system you will be using. Cleanroom classification standards started with the English system. The English system is the original system, but now-a-days you will find most people using the ISO systme. The cleanroom classification system estimates the number of various sized particles contained within one cubic foot of air. The amount of particles will determine the cleanroom classification. For example, what we mean when we say "Class 100" (English system) cleanroom, is that the most common particle count is greater than one-half micron, and that count should not be greater than 100 per cubic foot of air to meet Class 100 of the English classification system. The English Class 100 corresponds to the ISO Class 5.
In our example, we have established that in our Class 100 cleanroom we cannot have any more than 100 particles sized one-half micron or greater. We will determine that using a measurement tool because one-half micron particles are not visible to the naked eye. Measurement tools have greatly advanced in the last 5-10 years. The measurement tool is called an Air Particle Counter, APC. The APC has a sampling cone of a specific dimension and shape. Within the device there is a vacuum that draws in the sample across a laser where the particles are counted according to selected size. It is very important when using an APC to check the last calibration date displayed on the unit. Calibrations for air particle counters are only good for 12 months. Because this is a very sensitive instrument, it must be calibrated every 12 months. APCs are available in a three-channel model that can count particles of three different sizes during one sampling period. During typical operation, the unit will be programmed to sample the air over a one-minute period. The unit operator needs to only turn the unit on and press the "run" button. The proper way to use an air particle counter is to don the appropriate attire, wipe down the particle counter, and then take the particle counter into the cleanroom and do three sets of samples. The first set is taken "at rest" when the HEPA filters are on, but there are no process tools operating. Take particle counts at random areas around the cleanroom. The second particle count is taken when the HEPA filters are on and the process equipment is on. The third particle count is taken when the HEPA filters are on, the process equipment is on and the cleanroom operators are within the environment. This helps you isolate sources of potential contamination in your cleanroom environment.
In summary, to establish the cleanliness of your cleanroom you must first establish which cleanroom classification system you are going to use (English or ISO) and identify your cleanroom level. Once you know what level you must achieve, you must have the appropriate measurement tool. Using your properly calibrated measurement tool, you must do three counts within your cleanroom to determine the actual classification of the air in your clean room. Clean room classification readings will vary based on many variables which is why it is important that you have a very rigorous and accountable procedure regarding the frequency of your particle counts.
At Valutek we are dedicated to helping you maintain a compliant critical environment. Request your samples now!