Why Airlocks?

cleanroom door airlock

Ante Rooms Are So Important in GMP Facilities

Airlock systems play an important role in pharmaceutical industries, protecting clean rooms from contaminants, and preventing cross-contamination. As the name indicates, airlock refers to a locking system utilizing air pressure as a primary mechanism, as a means of protection in cleanrooms against contaminants during human and material movement. An airlock is produced by creating differential pressure between two areas, produced by the HVAC System.

The Design of Airlock:

An airlock is a closed room between two cleanrooms of different classes. Both doors of the airlock should not be opened simultaneously. Interlocking systems should be installed in airlocks to prevent the opening of both doors at the same time, with an alarm system that alerts the simultaneous opening of both doors should it occur. The doors of the airlock should be opened towards the higher-pressure side, so that it can easily be closed by air pressure.

The Principle of Airlock:

As we know, air moves from an area of higher pressure towards an area of lower pressure. All airlocks work on the same principle; changing the pressure in airlocks or in adjacent areas will produce different types of airlocks.

Types Of Air Locks

There are three types of airlocks:

cascade airlock

Cascade AirLock

In a cascade air locking system, pressure increases or decreases in ascending or descending order respectively, (from 30 Pa to 20 Pa to 10 Pa \or\ 10 Pa to 20 Pa to 30 Pa). Thus, air moves from higher pressure to lower pressure, preventing cross-contamination. This type of airlock is commonly used in Tablet manufacturing facilities where higher pressure remains in the corridor to keep drugs inside the cubicle.

bubble airlock

Bubble AirLock

In a bubble airlock, pressure inside the airlock is high or positive, and is low or negative on adjacent sides. Thus, 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, thus producing a bubble as it pushes air outside from the airlock. This type of Air locking system is commonly used in Injectable manufacturing facilities so that air contaminants from outside do not contaminate the product.

sink airlock

Sink AirLock

In sink airlocks, the pressure inside the airlock is negative, and is positive in adjacent areas, such that the air moves from higher pressure to lower pressure areas. Higher pressure on both sides of the airlock prevents contaminants from escaping the primary manufacturing area. It is commonly used in the manufacturing of harmful substances such as poison.

What are the driving factors need to consider into design for airlock?

Effective of Airlocks depending on its Design, operation, and maintenance. Each phase is described in below section.


  • Airlocks are basically work on the displacement principal. Air will flow from high pressurized space to the low pressurized space. According to ISO 146644-3 guidelines differential pressure between adjacent cleanroom or clean zone typically ranges of 5.0 Pa to 20.0 Pa which will allow smooth door opening and closing and avoid unwanted airflow due to turbulence.
  • Doors of the cleanroom should be airtight so that unwanted infiltration or exfiltration will not change the differential pressure. For achieving certain pressure inside the airlock supply or return cfm should be determine by adding or removing Leakage cfm.
leakage cfm
  • Orientation of Doors should be maintained in such as a way so that they will remain opened or closed due to pressure inside the rooms.
  • Airlock’s doors should have a window panel which help to provide sight of person from other side.


  • Doors should be operated in such a way then one door opened at one time otherwise it will lose differential pressure and allow the unwanted airflow.
  • Manual or automatic interlock need to provide to avoid operating both doors at same time. 
  • Magnehelic gauge or digital display should be installed which can provide accurate information of differential pressure.   
  • Nothing should be interfering in the closing and opening operation of doors.


  • There should be schedule airlock inspection to evaluate airlocks are working well or not.
  • Inspection of bottom seal sweeper, door closers, interlock and magnehelic gauge.