Door Interlocking In Pharmaceutical Industries

Different types of dosage forms are manufactured in the pharmaceutical industry and product quality is one of the most important factors which is ensured during product manufacturing.

Cross Contamination

During manufacturing, the product quality may be affected by the cross-contamination and to prevent cross-contamination an airlock system is built between different primary manufacturing areas and corridors.

Clean Rooms

As we know that clean rooms are the areas where viable and non-viable particles are kept under control & to protect the higher cleanroom class from less clean room class, airlock systems are built.

What Is an AirLock?

The airlock is a lock created by the air pressure between various clean rooms to maintain the status of a clean room or between different manufacturing areas to prevent cross-contamination. The airlock is the room which has two or more doors which open into various areas.

What Is Interlocking?

Interlocking is the concept which was introduced in pharmaceutical industries to make strong controls over cross-contamination by controlling the opening & closing of doors of airlocks, pass boxes and transfer hatches.

Interlocking is the locking system which is applied to the doors of airlocks to ensure that both doors are not opened at the same time.

Why Interlocking?

It is a common observation in pharmaceutical industries that most of the personnel don’t follow the strict SOPs of airlock passage which are as follows,

  • During man or material flow through the airlocks, always enter from one door and then close it tightly and when it is assured that the door is closed they open the next door.This procedure helps to prevent cross contamination due to differential pressure built inside the airlock & adjacent areas 

Wrong Practice

Apart from adopting the above-mentioned practice most of the personnel in pharmaceutical industries open both doors simultaneously which may result in following,

  • Movement of air from less clean areas to high clean areas.
  • Cross-contamination
  • Movement of  microorganisms from one clean room to another.

Working Principle Of Interlocks

  • Interlocking in pharmaceutical industries works on the principle of a mutual locking system meaning if one door is open, the other will not be opened.

Importance Of Interlocking

  • Nowadays installation of interlocking systems is the requirement of many regulatory bodies.
  • It gives alertness if any door remains open after a man or material flow.
  • Provide extra measures to prevent cross-contamination.
  • Installation of the interlocking system provides awareness to the working staff for proper usage of airlocks.
  • Apart from using interlocking in airlocks, this system is also used for different types of pass boxes installed in pharmaceutical industries.

Components Of Interlocking System

A good interlocking system has the following main components,

  • Electric Lock
  • Green Light
  • Red Light
  • Alarm
  • Control Panel

Electric Lock 

The main component of an interlocking system is an electric or magnetic lock which is opened & locked depending upon the usage. It is attached to the upper portion of the door to perform its functions.

Green Light

The lighting system is also used in the interlocking system to show the status of the door whether it is opened or closed. When the green light is on it means that the door is properly closed.

Red Light

Red light as we know is usually used for different kinds of alerts so in the case of an interlocking system when a red light is on, it means the door is open.

Red light is not only an indicator of the opening of the door, but it also gives alertness if the door is not properly closed due to any fault or reason.


An alarm system can also be used in an interlocking system to ensure the proper opening & closing of doors. 

As we know that booth doors should not be opened simultaneously so if anyone opens both doors at the same time an alarm rings.

Control Panel 

A control panel is used to control all the working of locks, lights and alarms.

An important note

Interlocking systems should be designed in such a way that during any emergency like a fire accident or electrical failure both locks should be in a neutral state to prevent any mishap & to allow easy escape of working staff.

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