The core principle of a positive pressurized container is to establish and maintain an internal pressure higher than the external environment. This prevents hazardous or toxic gases from entering, providing a clean and safe environment inside the box. The operating mechanism mainly includes the following aspects:

1. Establishing and Maintaining Positive Pressure

A positive pressurized container continuously supplies clean air into the container through an external air supply system (typically consisting of fans and air ducts).
  • Fan-driven Air Supply: Fans draw in external air and deliver clean air into the container.
  • Pressure Difference Maintenance: As the air volume inside the container increases and the exhaust rate remains slow, the internal pressure rises, forming a positive pressure higher than the outside.
  • Positive Pressure Effect: This pressure difference ensures airflow moves only from inside to outside, preventing external contaminated gases from entering.

2. Pressure Monitoring and Control

The positive pressurized container is equipped with differential pressure sensors and control systems to monitor the internal pressure in real-time.
  • Minimum Pressure Requirement: Considering adjacent spaces, the positive pressure system should maintain at least 25 Pa of pressure when 50% of all outlets (excluding doors) are open. A drop below 25 Pa indicates system failure.
  • Pressure Sensors: Measure the internal pressure and send data to the control system.
  • Alarm System: If the internal pressure becomes abnormal (too high or too low), the system triggers visual and audio alarms to alert operators for timely inspection.
  • Delay in Alarm Triggering: In case of door openings causing a temporary drop in pressure and external air entering the room, delayed alarms may be used. Door position sensors may be installed to verify the door status and airflow changes.

Note: Unless using a buffer room/air-lock door system, opening the door will reduce the pressure difference, potentially triggering unnecessary alarms.

3. Sealing and Airtightness

The structural design of the positive pressure box must ensure excellent airtightness to prevent pressure loss and the infiltration of pollutants.
  • Sealing Materials: High-performance rubber or silicone gaskets are commonly used at joints to ensure no air leakage.
  • Container Design: Precisely engineered frames and panels reduce gaps and enhance overall airtightness.

4. Temperature and Humidity Control

The air quality inside the positive pressurized container depends not only on filtration but also on temperature and humidity control (suitable for specific application scenarios).
  • Temperature Control: Some positive pressurized containers include heating or cooling systems to maintain optimal working temperatures.
  • Optional Humidity Adjustment: Dehumidification or humidification systems regulate air moisture levels, preventing overly dry or moist conditions from affecting operations or sample storage.

​5. Air Exchange Frequency and Volume

The air exchange efficiency of a positive pressurized container is a crucial performance indicator.
  • Air Change Frequency: Rapid air exchange removes polluted air from the container and replaces it with clean air. The air change rate should be at least five times per hour.
  • Air Volume: The positive pressure and overall manual ventilation system should provide an air exchange volume at least ten times the room’s capacity. Exceptions may be validated through analysis in accordance with standards GB/T3836.147-2019 like 6.4.4 or 7.5.3. 
  • Pollutant Removal: Under the influence of positive pressure and airflow, contaminants are quickly expelled by the exhaust system, ensuring a consistently clean environment.

Conclusion
The positive pressurized container ensures a clean and uncontaminated working environment through precise air supply, sealing design, and pressure monitoring. While preventing external pollutants, it maintains airflow direction, cleanliness, and a stable positive pressure state. These features make it widely used in industries such as pharmaceuticals, biotechnology, semiconductor manufacturing, and laboratory research.
 

TLS Offshore Containers / TLS Special Containers is a global supplier of standard and customised containerised solutions. 
Wherever you are in the world TLS can help you, please contact us.
 
 
Product brochures:
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MCC | Switchgear | VFD | VSD pressurised shelter
 
Keywords:#Hazardous Gas Prevention，#Pressure Difference，#Positive Pressure Effect，#Pressure Monitoring，#Differential Pressure Sensors，#Alarm System，#Sealing and Airtightnes
 
 

 

Written by Snowy