Cn =The maximum permitted concentration (in particles per cubic meter of air) of airborne which is rounded to the nearest whole number, using not more than three significant figures.
N = The ISO classification number, which shall be from 1 to 9.
D = The considered particle size, in micrometers i.e. 0.1 µm to 5.0 µm
0. 0.1 = A constant
Controlled areas are not only expensive to build but these are also more expensive to maintain. Following points should consider while designing the cleanrooms.
1. Air supplied through HEPA filters with high air changes to dilute and remove the particles and microbial contamination generated by personnel and the machinery.
2. The area should be constructed in such a way that the particles should not be generated and should be clean easily. Usually the material like metal id used for walls and ceiling while the floor should be of Vinyl of Epoxy.
3. The operators and other supporting staff should wear the covering clothes like mask and gloves etc. to minimize the dispersion of particles and microbes in area.
4. A positive should be maintained in area to avoid the entrance of particles and contamination through air.