What is Clean?
Clean is a relative term. Think about the cleanliness level in your home. Some rooms are cleaner than others. For instance, the kitchen is cleaner than the garage. This is because the activities that take place in these rooms are very different. When the door is open, dirt and leaves often gather in the garage. The kitchen is cleaner than the garage because the door to the kitchen is smaller and the kitchen is cleaned more frequently because it is used to prepare food. Like your house, laboratories and businesses have different levels of clean.
Standards are used in industry to give an accurate measure of the quality of a particular process or product. According to the dictionary a standard is “a degree or level of requirement, excellence, or attainment.” Science teachers rely on the National Science Education Standards to guide their teaching strategies, professional development, and support necessary to deliver high quality science education to all students. Standards also exist for cleanrooms. Federal Standard 209E establish standards for cleanliness for airborne particulate levels in cleanrooms. This document also describes methods for monitoring the air in the cleanroom and procedures for verifying the classification level of cleanrooms. Classifications of cleanrooms are established by the number of particulates that are one micron (μm) or larger
in a cubic foot of space per minute. One micron is equal to one millionth of a meter or 1/1000 millimeter. The chart below shows examples of common objects that are measured in microns.
Table 1: Examples of items measured in microns Example
Cigarette smoke particles
0.01 – 1
0.3 – 40
0.5 – 20
Diameter of human hair
40 - > 100