In cleanroom engineering, the Pass Box serves as a critical device for transferring materials between clean and non-clean areas, or between areas with different cleanliness classifications. Its function is essential for maintaining the stability of the cleanroom environment.

By minimizing personnel movement and reducing airflow disturbance caused by door opening, pass boxes effectively prevent cross-contamination. For many cleanroom facilities, they are an indispensable component for maintaining controlled environments.

For companies planning to purchase a pass box, understanding the different types and their application scenarios is the first step toward making the right decision. As a professional cleanroom equipment manufacturer, we have summarized the most common types of pass boxes available on the market for your reference.

1. Classification by Working Principle and Structure

This is the most common classification method and directly affects both the functionality and cost of the equipment.

1.1 Standard Pass Box (Mechanical Interlock Type)

Working Principle

This is the most basic model. Both doors of the pass box are equipped with a mechanical or electronic interlock system. When one door is opened, the opposite door is automatically locked and cannot be opened simultaneously. This prevents direct airflow between the two areas.

Application Scenarios

Suitable for environments where the cleanliness requirement is moderate and the primary purpose is physical separation. Typical examples include:

• Electronics manufacturing workshops

• General food processing clean areas

• Industrial cleanrooms

Features

• Simple structure

• Cost-effective solution

• Easy maintenance

• One of the most widely used pass box types

1.2 Clean Pass Box (With Air Purification System)

Working Principle

Based on the standard pass box design, this type includes a HEPA filter and fan system. When the pass box operates, the fan circulates air through the HEPA filter, purifying the air before supplying it into the chamber.

The system typically creates positive or negative pressure inside the chamber, blowing clean air across the material surface to remove dust particles.

Application Scenarios

Ideal for environments that require strict contamination control, such as:

• GMP pharmaceutical production workshops

• Biological laboratories

• Precision electronics manufacturing

Features

• Self-cleaning capability

• Reduces particle contamination on materials

• Often equipped with a differential pressure gauge to monitor filter resistance

1.3 Laminar Flow Pass Box (Unidirectional Airflow Pass Box)

Working Principle

This is an upgraded version of the clean pass box. The fan and HEPA filter are installed at the top of the chamber, generating a vertical unidirectional airflow (laminar flow) without turbulence.

The uniform airflow moves across the material surface, effectively removing contaminants.

Application Scenarios

Suitable for highly controlled environments such as:

• Grade A/B sterile cleanrooms

• Pharmaceutical aseptic production areas

• Sensitive material transfer applications

Features

• Superior purification performance

• Can provide ISO Class 5 (Class 100) or higher local clean environment

2. Classification by Chamber Material

Material selection mainly depends on cleanroom standards, durability requirements, and cleaning convenience.

2.1 Powder-Coated Cold-Rolled Steel Pass Box

Features

The chamber is constructed from high-quality cold-rolled steel sheets treated with acid pickling, phosphating, and electrostatic powder coating.

• Lower cost

• High structural strength

• Suitable for general industrial environments

Applications

Commonly used in general industrial cleanrooms where corrosion resistance requirements are not extremely strict.

2.2 Stainless Steel Pass Box (SUS304 / SUS316L)

Features

Manufactured entirely from stainless steel sheets.

• Excellent corrosion resistance

• Smooth surface without dead corners

• Easy to clean and disinfect

• Fully compliant with GMP standards

Applications

Widely used in industries requiring high hygiene standards, including:

• Pharmaceutical manufacturing

• Biotechnology

• Medical facilities

• Cosmetics production

• Food processing

Among them, SUS316L is often used in environments involving strong chemicals or highly corrosive conditions.

3. Classification by Interlock System

The interlock mechanism is the core component of a pass box and determines operational safety and reliability.

3.1 Mechanical Interlock Pass Box

Working Principle

The interlock is achieved through a purely mechanical mechanism such as rods or locking hooks. When one door is opened, the mechanism physically blocks the other door from opening.

Features

• Extremely reliable structure

• Not affected by electronic failures

• Slightly heavier operation

• Limited electronic integration capabilities

3.2 Electronic Interlock Pass Box

Working Principle

The interlock function is controlled through electromagnets, micro switches, and electronic control circuits. When one door is opened, the system automatically cuts power to the electromagnetic lock of the other door.

Features

• Smooth and convenient operation

• Fast response time

• Easy integration with additional functions such as:

• UV sterilization control

• Access control systems

• Status indicator lights

This type is currently the most widely used solution in the market.

4. Additional Functional Features

Modern pass boxes can be equipped with additional features to improve safety and efficiency.

UV Sterilization Function

UV lamps are installed inside the chamber to provide auxiliary sterilization for material surfaces. This is standard in pharmaceutical and medical applications.

Intercom System

Allows operators on both sides to communicate easily during the transfer process.

Voice Reminder System

Provides voice alerts when improper operations occur, such as leaving the door open for too long, helping standardize operating procedures.

Pass Box Selection Recommendations

When selecting a pass box, we recommend considering the following factors:

1. Cleanroom Classification

• Basic isolation → Mechanical interlock pass box

• Surface decontamination → Clean pass box

• Sterile environments → Laminar flow pass box

2. Industry Regulations

Pharmaceutical facilities should select stainless steel pass boxes with UV sterilization to meet GMP requirements.

3. Material Size

Choose the pass box chamber size according to the largest material dimensions to be transferred.

4. Usage Frequency

For high-frequency operations, electronic interlock systems are recommended for easier and more efficient operation.

Professional Cleanroom Pass Box Manufacturer

As a professional cleanroom equipment supplier, we provide a full range of pass boxes with multiple specifications and customization options. Our products strictly comply with GMP standards and have been widely used in pharmaceutical, electronics, and biotechnology industries.

If you have specific purchasing requirements or technical questions, please feel free to contact us for consultation.