What Is A Cleanroom Airlock?

Airlocks are used to keep contaminants out of cleanrooms when personnel enter or exit a cleanroom or when material is brought into or taken out of cleanrooms. Only 1 door is opened at a time to prevent contaminants from having a straight path into the cleanroom. Air locks typically have HEPA filtration to remove contaminants from inside the airlock and interlocked doors to ensure that only one door can be opened at a time. Types of airlocks include personnel airlocks, material transfer airlocks, pass thru’s, and air showers.

Figure 2 shows a study on the effectiveness of doors and airlocks in preventing particles from entering cleanroom from outside. A single door will prevent 80% of particles from entering the cleanroom. An airlock with 2 doors (no HEPA filtration) will prevent 96% of particles from entering the cleanroom. Adding HEPA filtration to the airlock will prevent even more of particles from entering the cleanroom.

Personnel Air Lock (PAL) are often called gown rooms since they serve the dual purpose of providing a clean area for personnel to put on their cleanroom garments and providing a barrier to particles entering the cleanroom when personnel enter and leave.

Material Air Locks (MAL) are air locks designed to bring material in and out of cleanrooms while providing a barrier to particles entering the cleanroom. Larger ones often use interlocked motorized roll up doors and have HEPA filtration. Smaller ones can use less expensive swing doors and may or may not have HEPA filtration.

Pass thru’s are a smaller type of material airlock. They typically use mechanical interlocks to prevent both doors from being open at same time. Cart pass thru’s are designed to allow the use of carts to move larger quantities of materials in and out of cleanrooms. Pass thru’s can have HEPA filtration added if desired.

Cleanroom Interlocks are often used on airlocks to prevent both doors from being opened at same time. Electronic interlocks consist of mag locks, sensors and PLCs are used for swing doors. Motorized roll up doors electronic controls can be wired to prevent both doors from being opened. Pass thru’s typically use less expensive mechanical interlocks. 

Another method cleanrooms use to keep particles out the cleanroom is positive pressure. Most cleanrooms are designed so cleanroom airlock is higher pressure than outside the cleanroom. If you open the door the air flow is out of the airlock so less particles enter. Likewise, the cleanroom is typically higher pressure than the airlock so when you open the interior airlock door air flows out of the cleanroom into the airlock so less particles enter. This is called a cleanroom pressure cascade.

Cleanroom air Showers are another type of airlock typically used in series with gown room airlock. Air showers use high velocity HEPA filtered air to blow particles off cleanroom garbed personnel as they enter the cleanroom. Additionally, the air showers doors are interlocked to prevent both doors from being open at same time. A new trend is to use air showers for material pass thru’s to combine the airlock functionality with cleaning material before bringing the material into the cleanroom.

Summary: Airlocks are used to prevent particulates from entering cleanrooms when personnel enter or exit cleanroom or when material is brought into or brought out of cleanrooms. They have 2 doors with only one being opened at a time. Personnel airlocks (PALs)  are typically called gown rooms while smaller material airlocks (MALs) are often called pass thrus and larger ones called material transfer rooms. Features include door interlocks, HEPA filtration, and air showers.

Author: The author Anthony Chien has worked at American Cleanroom Systems for past 12 years.  He has more than 40 years of cleanroom experience. Anthony has a BS and MS in Electrical Engineering specializing in semiconductor manufacturing from the University of Illinois. American Cleanroom Systems is a design build modular cleanroom manufacturer based in Rancho Santa Margarita CA. It is expert in ISO-5 through ISO-8 (class 100 to class 100k) modular cleanrooms for pharmaceutical cleanrooms, medical device cleanrooms, and industrial cleanrooms.