Design of Clean Air Conditioning for Microbiology Laboratory

Microbiology laboratories conduct experiments and research on microbial isolation, cultivation, identification, morphology, utilization, variation, and hazards. What functional rooms are required for construction? How to design the air conditioning system? This article reveals the answers.

Main functional rooms include preparation room, buffer room, sterile room, cultivation rooms (bacterial, fungal, TB cultivation rooms), identification room, cleaning/disinfection room, reagent room, and strain storage room. Composition and scale may vary based on application (testing, teaching, research, monitoring).

(1) Biosafety Levels

Microbiology laboratories primarily examine pathogenic microorganisms, focusing on infectious diseases and hospital-acquired infection monitoring. Clinical microbiology testing ensures rational antimicrobial use. Conventional laboratories comply with Biosafety Level 2 (BSL-2). Medical BSL-2 labs are classified into standard and enhanced types, with key technical requirements compared below:

 

Standard BSL-2 labs have simpler design requirements. Mechanical or natural ventilation is acceptable.

Enhanced BSL-2 labs require mechanical ventilation. Core workspaces must not have openable windows. Buffer rooms are installed at entrances. Core workspaces maintain negative pressure with visible pressure displays. Exhaust systems install HEPA filters. Fresh air systems are recommended to control humidity and pressure gradients.

(2) Air Conditioning Load Calculation

Loads include building envelope load, fresh air load, lighting load, equipment load, personnel load, and other loads. Biosafety labs have significantly higher loads than offices due to:

Heat emission from lab equipment: High-heat devices (ultra-low temperature freezers, centrifuges, CO₂ incubators, autoclaves) increase sensible heat load.

Fresh air compensation: Local exhaust equipment (e.g., biosafety cabinets) requires additional fresh air beyond personnel needs to maintain room air balance.

(3) Ventilation and Air Conditioning Systems 

Standard BSL-2 labs offer flexible design options: all-air systems, air-water systems, VRF systems, or split units based on technical-economic analysis. Enhanced BSL-2 labs typically use all-air (100% fresh air) systems. Air change rates: 6-12 times/hour, determined by load, procedures, and material risk levels.

When using externally vented biosafety cabinets:

· Exhaust via ducts independent of building ventilation.

· If shared with lab exhaust, fan pressure must overcome cabinet resistance (~500Pa).

Separate exhaust systems for cabinets and labs require interlock control: cabinet exhaust activates first and deactivates last to prevent backflow. Enhanced BSL-2 labs need HEPA filters on exhaust and backup fans.

All labs must ensure directional airflow from low-to high-contamination zones. Avoid dead zones or vortices. Do not install supply outlets above biosafety cabinets or aerosol sources. Per GB50346-2011:

Exhaust outlets in ceiling-supply/floor-return systems:

Lower edge: 0.1-0.15m above floor

Upper edge: ≤0.6m above floor

Exhaust velocity ≤1m/s.