Airlocks in pharmaceutical Industries

Airlock system plays an important role in pharmaceutical industries to protect clean rooms from contaminants and to prevent cross-contamination.

As the name indicates, airlock means a locking system which is produced by utilizing air pressure. In simple words, we can say that the airlock system is a locking system for the protection of clean areas from contaminants which can contaminate the clean rooms during men and material flow.

An airlock is produced by creating differential pressure between two areas and differential pressure is produced by HVAC.According to WHO a differential pressure of 10-15 pascals should be maintained. To produce a higher differential pressure cost of the system is also increased.

Purpose of Airlock

  • The main purpose of the airlock system is to prevent cross-contamination.

  • To prevent the entry of contaminants from less classified area to a highly classified area.

  • In a sterile area prevent the entry of less clean air to high clean area.

  • In a sterile area prevent the entry of microbes from the less clean area to the high clean area. 

  • In oral solid dosage forms, manufacturing areas prevent the outflow of powders.

In most of the pharmaceutical industries, a common airlock system is used for the entry of men and materials it is wrong practice.

Personnel Airlock (PAL)

The airlocks which are used for the entry of personnel into the cleanroom is called personnel airlock (PAL).

Material Airlock(MAL)

The airlock which is used for transferring of materials is called Material air Lock (MAL).

Design of Air Lock

The airlock is a closed room between two cleanrooms of different classes for example between Cleanroom Class B and cleanroom class C and same way between Class C and Class D.Air lock is usually with two doors one door open in one clean room like in class C and other door opens in another class area like in class  D.So if we want to enter from class D to class C, first of all, we will enter from Class D into Airlock and then from the airlock to Class C.

Both doors of airlock should not be opened simultaneously. First Of all open one door and enter into airlock from Class D then close that door and open other door to enter into Class C.Interlocking system should be installed in airlocks to prevent the opening of both door at the same time. An alarm system should be installed which give an alert if both doors are opened at the same time. The doors of air look should be opened towards higher pressure side so that it can easily be closed by air pressure. The airlock should always be free from any furniture, chairs, table, shoe covers etc.

Principle of Air Lock

As it is a general role that air moves from an area of higher pressure towards the area of lower pressure. So all airlocks work on the same principle just we have to change the pressure in airlocks or in adjacent areas to change the type of airlock either it is a bubble, sink or cascade. 

Types Of Air Locks

There are three types of an airlock system

  • Bubble Airlock

  • Sink Air Lock

  • Cascade Air Lock

Bubble Air Lock  

In bubble airlock pressure inside the airlock is high or positive and in adjacent sides, the pressure is less or negative.

For example in airlock pressure is 20 Pa and in both the sides, the pressure is 10 Pa so air moves from 20 Pa(Airlock) to 10Pa in (adjacent sides). Mean air moves from the airlock to the primary manufacturing area and in the same way from the airlock to the corridor. Higher air changes are produced in the airlock. It is called bubble because it pushes air outside from the airlock.

Sink Air Lock

In sink airlock, the pressure inside airlock is negative and in adjacent areas pressure is positive so air moves from higher pressure area to lower pressure area mean from adjacent rooms to the airlock.

For example in airlock pressure is 10 Pa and in both sides, the air pressure is 20 Pa so air moves from 20 Pa(Adjacent sides ) to 10Pa in (Airlock). Mean air moves from Adjacent areas to airlock e.g from the primary manufacturing area to airlock and in the same way from the corridor the airlock. It is called sink because the air from both sides come into the airlock.

Cascade Airlock

In cascade airlock system pressure increases or decreases in ascending or descending order for example from 30 Pa to 20 Pa to 10 Pa or 10 Pa to 20 Pa to 30 Pa. So air moves from higher pressure to lower pressure side and prevent cross-contamination.


Take the example of a  simple layout, we have one primary room where we want to manufacture the product for example granulation area of tablet manufacturing section. Outside the primary room is a corridor and on other side of the corridor is compression room so we want to prevent cross-contamination of granulation area to compression room or from compression room to granulation room. we will build an airlock room between granulation room and corridor and in the same way between corridor and compression room.

we can prevent cross-contamination either by maintaining Bubble or cascade airlock system.

For Bubble Air Lock

Suppose we want to prevent cross-contamination by Bubble airlock for granulation area, we will build an airlock room between granulation area and corridor and create positive in airlock pressure by supplying more air through HVAC say it is 20 Pa. In granulation room produce 10 Pa so when we will open the door, clean air will move from airlock to granulation area and powders from granulation will not enter to airlock because of differential pressure. In the same way in corridor create 10 Pa so when we will enter from corridor the clean air from air look will move into the corridor.

If inside granulation room is positive e.g 20 Pa and in the lock is 10 Pa the powder from granulation area will enter in the airlock and if in the corridor is 8 Pa then this powder will move from airlock to corridor and will contaminate other areas.

For Cascade Airlock

Cross-contamination can also be prevented by creating a cascade airlock. For cascade airlock inside of granulation area is maintained negative for example at 10 Pa and airlock is maintained at more positive e.g 20 Pa and corridor is maintained at 30 Pa mean highly positive. According to principle air will move from higher pressure to lower pressure 

so air will move from corridor to airlock and from airlock to manufacturing area. In this case, the corridor will be cleaned corridor having high air changes.

Also Read:

Clean rooms classification in pharmaceutical industries.

In oral solid dosage form areas, we keep inside of the manufacturing area at negative pressure to prevent our flow of powders.

So critical monitoring of air pressure maintenance is required in all areas because any drop or increase in the pressure of any area may result in cross-contamination.

For sterile areas inside is maintained at positive pressure, so air moves from the high clean area to outside low clean area.

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