An Overview of ISO 14644 Clean Room Classification
All classes of clean rooms, airborn particles and formula to calculate the number of sampling locations.
The area having controlled airborne particle concentration is considered as the clean zone or clean room. These areas are constructed to minimize the introduction, generation, and retention of airborne particles in the area.

The concentration of particles depends on their diameter; hence the bigger particles will be less in number than the smaller particles in any clean room environment.

The airborne particles play a considerable role in aseptic processing because the viable particles i.e. bacteria, fungus etc. are associated with non-viable particles and may cause
contamination in pharmaceutical sterile preparations.

Classification of these areas are given in many guidelines but the base of all other guidelines is ISO i.e. ISO-14644-1. A proper classification is given in ISO with the formula which gives the concentration of airborne non-viable particles in any class.

Table 1 shows the different classes of clean rooms.

There are 9 classes of clean rooms in ISO but only ISO Class 5 to ISO Class 8 for 0.5 μm and 5.0 μm are applicable in pharmaceuticals. These numbers of particles are calculated for every class and for all particle sizes by the formula given below-

Where,
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 clean rooms.

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 the area.

4. A positive should be maintained in the area to avoid the entrance of particles and contamination through the air.

Also see:Clean Rooms And Controlled Areas (Sterile Area)