ISO 14644 Clean Room Classification

What is Clean Room :

A clean room is designed in such a way which is having the provisions to reduce or control particulate contamination and to maintain the environmental parameters such as temperature, humidity and Differential pressure.

Clean room is a controlled environment that has a low level of pollutants such as dust, airborne microbes, aerosol particles, and chemical vapors and has a controlled level of contamination that is specified by the number of particles per cubic meter at a specified particle size.

The High Efficiency Particulate Air (HEPA) filter is used to trap particles that are 0.3 micron and larger in size.

All of the air delivered to a clean room passes through HEPA filters, and in some cases where stringent cleanliness performance is necessary, Ultra Low Particulate Air (ULPA) filters are used.

Clean rooms can also use ultraviolet light to disinfect the air and UV devices can be fitted into ceiling light fixtures and irradiate air, killing potentially infectious particulates, including 99.99 percent of airborne microbial and fungal contaminants.

Where clean Rooms are Used:

Clean rooms are used in industries where small particles can adversely affect the manufacturing process. They vary in size and complexity, and are used extensively in industries such as pharmaceuticals, biotech, medical device, Operation theaters (OT) and life sciences, as well as critical process manufacturing common in aerospace, optics, military and Department of Energy.

History of Clean room :

The modern clean room was invented by American physicist Willis Whitfield and he was the employee of the Sandia National Laboratories, Whitfield created the initial plans for the clean room in 1960.

Personnel Contamination in Clean room :

The greatest threat to clean room contamination comes from the users themselves.

In the healthcare and pharmaceutical sectors, control of microorganisms is important, especially microorganisms likely to be deposited into the air stream from skin shedding. Studying clean room micro flora is of importance for microbiologists and quality control personnel to assess changes in trends.

In assessing clean room microorganisms, the typical flora are primarily those associated with human skin (Gram-positive cocci), although microorganisms from other sources such as the environment (Gram-positive rods) and water (Gram-negative rods) are also detected, although in lower number.

Clean room Air Flow Principles:

Clean rooms maintain particulate-free air through the use of either HEPA or ULPA filters employing laminar or turbulent air flow principles.

Laminar, or unidirectional, air flow systems direct filtered air downward in a constant stream and this systems are typically employed across 100% of the ceiling to maintain constant, unidirectional flow. Laminar flow criteria is generally stated in portable work stations (LF hoods), and is mandated in ISO-1 through ISO-4 classified clean rooms.

Classification of Clean Room:

The clean room classification standards FS 209E and ISO 14644-1 require specific particle count measurements and calculations to classify the cleanliness level of a clean room or clean area. Classification of area are given in many guidelines but the base of all other guidelines is ISO-14644-1.

As we know that there are 9 classes of clean rooms in ISO but in pharmaceuticals mostly ISO Class 5 to ISO Class 8 are used for 0.5 μm and 5.0 μm.

ISO-14644-1 defines the maximum concentration of particles per class and per particle size. The below table shows the different classes of clean rooms accordingly to ISO-14644-1 Standards.

EU GMP classification:

EU GMP guidelines are more stringent than others, requiring clean rooms to meet particle counts at operation (during manufacturing process) and at rest (when manufacturing process is not carried out, but room AHU is on).


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