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Animal Facility Air Purification & Airflow Design: Key Technologies for Pressure Control and Pathogen Prevention

Created on 02.05
Animal research facilities are critical infrastructure for life science research and biopharmaceutical development. Environmental quality directly affects animal welfare, the reliability and reproducibility of experimental data, and overall biosafety. Designing an efficient airflow system that integrates air purification, pressure control, and pathogen isolation is the cornerstone of safe and stable animal facility operation.
This article provides an in-depth analysis of three key technologies: high-efficiency air supply combined with laminar (unidirectional) airflow design, room pressure gradient control, and strategies to prevent cross-transmission of pathogens.
Stainless steel pass-through chamber with digital display and secured glass door.

I. High-Efficiency Air Supply & Laminar / Unidirectional Flow Design: The “Highway” of Clean Air

1. High-Efficiency Air Supply Systems

Animal facilities require a continuous supply of highly filtered clean air. A three-stage filtration system—pre-filter, medium filter, and high-efficiency particulate air (HEPA) filter—is commonly adopted. This configuration effectively removes particles ≥0.3 μm with an efficiency of 99.99% or higher, eliminating most airborne dust, microorganisms, and aerosols.
Core objectives of high-efficiency air supply:
  • Deliver stable, uniform, and sufficient clean air
  • Rapidly dilute and remove indoor contaminants such as odors, hair, and microorganisms

2. Laminar Flow and Unidirectional Flow

  • Laminar flow:
Air moves in parallel streams at a uniform velocity and in a single direction, forming an “air curtain.” It is widely applied in critical clean operation zones such as IVC cage-changing stations and animal surgical tables, creating localized ultra-clean micro-environments to protect both animals and operators.
  • Unidirectional flow:
A broader concept referring to guiding overall airflow in a predetermined direction through strategic placement of supply and return air outlets—typically from clean areas toward contaminated areas. In whole-facility layouts, single-direction airflow prevents backflow and short-circuiting.
Key advantages:
  • Efficient contaminant removal: Pollutants are discharged along the designed airflow path, preventing diffusion within the room
  • Enhanced animal protection: Reduced risk of cross-infection, especially critical for SPF (Specific Pathogen Free) animal housing
  • Energy-saving potential: Optimized airflow organization can maintain cleanliness while reducing air volume and energy consumption
Laboratory storage room with shelves of yellow containers.

II. Room Pressure Gradient Control: An Invisible “Isolation Barrier”

Pressure differentials are a fundamental method for preventing air cross-contamination. By controlling pressure differences between adjacent rooms, airflow is forced to move only from clean zones to potentially contaminated zones.

1. Principles of Pressure Design

  • Positive and negative pressure:
    • Positive pressure areas (e.g., clean corridors, animal holding rooms) prevent external contaminated air from entering
    • Negative pressure areas (e.g., quarantine rooms, infection experiment rooms, dirty corridors) prevent internal contaminants from escaping
  • Pressure gradients: A typical animal facility pressure cascade is:
Clean preparation area (highest pressure) → Clean corridor → Animal holding room → Dirty corridor → Washing & disinfection area (lowest pressure)
Adjacent rooms usually maintain a pressure difference of 10–15 Pa.

2. Key Technical Measures

  • Automatic control systems: Integration of pressure sensors, variable-frequency fans, and motorized dampers enables real-time monitoring and automatic adjustment of supply and exhaust air volumes to maintain stable pressure differentials
  • Airtight construction: Doors, windows, wall penetrations, and joints must be carefully sealed to prevent air leakage that could compromise pressure control
  • Airlocks / buffer rooms: Installed between areas with large pressure differences to minimize pressure fluctuations and air exchange during door opening

III. Preventing Pathogen Cross-Transmission: A Systematic Control Strategy

Pathogens can spread via air, contact, and personnel movement. Therefore, airflow design must work in coordination with operational and management measures.

1. Blocking Airborne Transmission

  • Directional airflow design: Ensure air always flows from healthy animal areas toward quarantine or infection experiment zones, with no reverse flow
  • Exhaust air treatment: Exhaust air from infectious animal rooms must pass through HEPA filtration or thermal inactivation before discharge
  • Individually Ventilated Cages (IVC): Providing independent supply and exhaust air to each cage creates micro-isolation, effectively preventing cage-to-cage cross-infection

2. Control of Personnel and Material Flow

  • Separation of people, materials, and animals: Dedicated routes are designed to avoid crossing paths
  • One-way movement principle: Personnel and materials must move from clean to dirty areas; return requires thorough disinfection or transfer via pass boxes or transfer hatches

3. Monitoring and Maintenance

  • Continuous monitoring: 24/7 monitoring and recording of pressure differentials, temperature, humidity, and cleanliness levels
  • Regular validation: Includes airflow visualization (smoke tests), HEPA leak testing, and pressure recovery tests to ensure systems operate as designed
  • Strict maintenance: Periodic replacement of filters, duct cleaning, and fan maintenance to prevent performance degradation

Conclusion

The air purification and airflow system of an animal facility is a highly sophisticated environmental control project. High-efficiency air supply and laminar/unidirectional flow form the foundation by providing clean air; pressure gradient control acts as the central “command system,” directing airflow in an orderly manner. Together, they serve the ultimate goal of preventing pathogen cross-transmission.
Only by integrating these technologies with rigorous operational management can a safe, reliable, and efficient animal research environment be established—providing solid support for scientific research and the advancement of the biopharmaceutical industry.
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