According to on-site inspection reports, a significant percentage of workshops are currently suspended or delayed from certification due to faulty airflow design causing cross-contamination in the analytical culture area. Suboptimal cleanroom layout planning for microbiological testing directly leads to inaccurate test results.

Designing a standard quality control system requires strict adherence to GMP cleanroom standards. The problem of unidirectional airflow distribution and technical pressure gradient needs to be thoroughly addressed.

This article provides a detailed layout plan based on current international standards. We will explore the optimal arrangement and integration of supporting equipment from Duc Duong to pass the audit.

1. Dust Particle Limit Classification

1.1 Microparticle Density According to WHO GM

Cleanroom quality management systems classify the environment based on the density of airborne particles. According to the World Health Organization (WHO-GMP Annex 2) guidelines, the hardware system establishes four cleanliness levels in GMP factories: Grade A, Grade B, Grade C, and Grade D. Each classification requires strict control over the maximum allowable number of dust particles in both at-rest and in-operational states.
For particle sizes >= 0.5 mu, GMP cleanliness levels stipulate that Grade A must be below 3,520 particles/m³ in both states. Meanwhile, Grade B in the operating state allows up to a maximum of 352,000 particles/m³. This particle grading is the core foundation for mechanically removing suspended contaminants and preventing fungal spores from adhering to the agar plates.

1.2 Establishing a Local Grade A Zone on a Grade B Base

Sensitive sample transfer and contamination testing operations require an absolutely sterile environment. We plan a localized, closed Grade A (Class 100) ultra-clean zone directly on a Grade B cleanroom base.
This fluid dynamics combination completely isolates the culture area from external microbial fluctuations. The GMP cleanliness level in this zone limits the number of colonies (CFU) obtained through air agar plates to below 1 CFU to eliminate the risk of false positives.

2. One-Way Flow Planning

2.1 Establishing a Forward Flow Sequence

The operation of a test cleanroom must strictly adhere to the principle of one-way forward flow. The standard floor plan establishes a continuous flow path from the zone with the lowest cleanliness level to the zone with the highest cleanliness level: Airlock -> Culture Preparation Room -> Microbiology Room.

Inspectors move sequentially through separate changing rooms (Clothing Rooms) to mechanically disinfect their clothing. This planning principle prevents personnel from moving in the opposite direction, causing disruption and carrying dirt from the raw area into the clean area.

2.2 Application of Pass-Box for Isolation of Materials

The transfer of glassware and test samples between different cleanroom zones is carried out via a sample transfer box (Pass-box). This device is installed through the isolation partition between the instrument preparation room and the sterile microbiological inoculation room.
The integrated door system with a mechanical interlock mechanism ensures that two doors cannot be opened simultaneously. This technical solution completely prevents free pressure drop in the cleanroom and eliminates the risk of convective leakage of contaminated air between rooms.

3. Establishing a Differential Pressure System

3.1 Standard Positive Pressure Slope in Microbiological Cleanrooms

To create an aerodynamic barrier protecting the sterile environment, the microbiological inoculation room must maintain the highest positive pressure slope. The standard differential pressure index is controlled to fluctuate from +10 Pa to +15 Pa relative to the adjacent dressing room.

This gradient pressure model ensures a continuous, high-pressure airflow from the cleaner zone to the cleaner zone when the airlock is opened. This physical principle sweeps away suspended dust particles, completely eliminating the risk of reverse entry of bacteria from the corridor.

3.2 Controlling the Air Exchange Rate via AHU HVAC

The central air conditioning system (AHU/HVAC) is responsible for continuously maintaining airflow for the entire area. For Grade B and Grade C cleanrooms, the mechanical and electrical (M&E) system needs to establish a standard air exchange rate of 20 to 40 times/hour.

We distribute supply air vents evenly on the ceiling panels and return air vents near the floor. This fluid flow separation forces all dust particles to move downwards in a gradient, optimizing the self-cleaning ability of the lab.
Are you looking for a solution to synchronize your HVAC system and design a 3D perspective drawing of a one-way cleanroom for testing that meets stringent GMP inspection requirements? Please fill out the Contact Us form directly to receive in-depth cleanroom standards documents and a free consultation from our project engineers.

4. Synchronizing the configuration of the culture cabinet

4.1 Mechanical dust particle separation mechanism of HEPA H14 filter

The process of transferring and isolating microbial strains requires an absolutely sterile working area, Class 100. The LM-1800V microbiological culture cabinet distributed officially by Duc Duong is the ideal hardware solution to meet this configuration.
The equipment parameter data axis is directly linked to the website of the international manufacturer LK Lab Korea. The technological pillar of the cabinet is the HEPA H14 filter, which performs mechanical dust particle separation with a high efficiency of >= 99.995% for particles of 0.3 mu size. The ultra-clean airflow completely removes all suspended mold spores and exotoxins, protecting the agar plate safely.

4.2 Forward Airflow Speed ​​for Sample Protection

The laminar airflow mechanism of the cabinet maintains a stable and continuous airflow velocity between 0.3 m/s and 0.5 m/s. The vertical forward airflow sweeps across the work surface, preventing the breath of the tester from contaminating the agar samples.
The system incorporates a short-wavelength UV lamp (253.7 nm) to perform an effective sterilization cycle of the work chamber before work begins. This synchronized mechanical and physical combination eliminates contaminants, maximizing the accuracy of the test.

5. Aerosol Contamination Control

5.1 Mechanism of Toxic Aerosol Formation from Micropipettes

In a sterile cleanroom environment, the tester’s manipulation behavior is the largest source of trace contamination. When performing liquid sample dosing using a piston volumetric device, pressing and releasing the button too quickly can easily break the fluid structure.
This mechanical tearing force transforms a portion of the culture solution into ultrafine aerosol particles that disperse freely into the air. These microbial aerosol particles, carried by the convection current, adhere to the panel walls or adjacent surfaces, creating an extremely dangerous risk of cross-contamination within the system.

5.2 Standard Operating Procedure for Piston-Type Volumetric Instruments

To thoroughly control aerosols, laboratory personnel must strictly adhere to the 17 points to note when using Duc Duong micropipettes. The standardized SOP requires holding the pipette shaft vertically at a 90-degree angle, releasing the button slowly, and dispensing the solution slowly along the test tube wall.

We should use tips with mechanical particle filters to retain micro-droplets. Micropipette equipment must be made of heat-resistant material, allowing for complete sterilization at 121°C to ensure sterility.

6. Cleanroom Measurement Schedule

6.1 Frequency of Measurement and Classification of Microscopic Dust Particle Density

After commissioning, sterile cleanroom systems need to be continuously monitored and re-validated. According to the national standard TCVN 8664-2 (equivalent to ISO 14644-2), the measurement of particulate matter concentration and HEPA filter leakage testing must be performed every 6 to 12 months.

In addition, the mechanical and electrical engineers need to perform a cleanroom recovery test. This test accurately assesses the ability of the AHU to self-clean dust generated during the work shift, ensuring the room returns to its resting state within 15-20 minutes after personnel leave.

6.2 Digitizing Daily Differential Pressure Parameter Logs

Environmental parameter monitoring records are the most important legal evidence in GMP inspections. The QC lab needs to be equipped with an automatic measurement sensor system and digitize daily logs recording differential pressure, temperature (22°C ± 2°C), and humidity (50% ± 5% RH).

The closed-loop data storage, which cannot be manually edited or deleted, ensures absolute data integrity. This is a prerequisite for a microbiology laboratory to achieve the stringent ISO 17025 certification.

Conclusion

The construction of infrastructure and functional planning of the lab according to GMP cleanroom standards requires a synchronized and precise technical mindset. The core principles include strict particle size distribution from Grade A to Grade D, one-way airflow planning through a closed-loop airlock system, positive pressure control with a slope of +10 Pa to +15 Pa, synchronized installation of LK Lab microbiological inoculation cabinets for mechanical separation of contaminants, standardized micropipette operation for aerosol removal, and rigorous implementation of the 17025 periodic measurement cycle. Duc Duong Company is proud to offer a comprehensive turnkey solution for cleanroom design and construction, providing high-quality, officially licensed equipment, and fully supporting your company’s journey towards achieving international quality certification.

To receive a free guide to calculating cleanroom HVAC airflow and a 3D microbiological zone layout drawing, please register your information directly at DUC DUONG SCIENCE AND TECHNOLOGY COMPANY so our project specialists can provide in-depth assistance.

 

DUC DUONG SCIENCE AND TECHNICAL COMPANY

Address: 1014/67 Tan Ky Tan Quy, Binh Hung Hoa, Binh Tan, HCM

Tel: (028) 3762 8042 – 3762 8043 – 3750 8514 – 3750 8793

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Email: ducduong@ducduongco.com

Website: ducduongco.com

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FAQ

1. Why is it mandatory for personnel movement in a microbiological cleanroom to pass through an airlock changing room system?

The airlock changing room system acts as a physical barrier, isolating the microbiological cleanroom from the outside raw material storage corridor. As inspectors move in a one-way direction through the closed airlock doors, the positive outward pressure will dislodge all dust particles adhering to the clothing, preventing cross-contamination of the airflow carrying microorganisms from entering the cleanroom.

2. What is the difference between the at-rest and in-operational states of a GMP cleanroom?

The at-rest state is when the cleanroom HVAC system is operating stably, the cleanroom has all the necessary hardware equipment, but no personnel are operating it. The in-operational state is when the cleanroom has all the necessary machinery and materials, and the maximum number of personnel are performing actual tests according to the standard SOP procedure.

3. How does the LM-1800V vertical laminar flow microbiological culture cabinet create a locally sterile Grade A environment?

The LK Lab series of microbiological culture cabinets distributed by Duc Duong utilizes a fluid convection fan system that forces the airflow through a dense fiberglass HEPA H14 filter. This mechanical separation process retains >= 99.995% of ultrafine dust particles and mold spores as small as 0.3 µm, creating an ideal vertical airflow that continuously sweeps across the agar plate surface, completely isolating the working area to achieve a Class 100 ultra-clean, bacteria-free environment.

4. How does the aerosol dispersion phenomenon when using micropipettes in a cleanroom pose a risk to testing?

When the tester presses and releases the piston button too quickly or forcefully discharges the last drop of fluid from the plastic tip, the mechanical tearing will cause some of the culture solution to be dispersed into microscopic aerosol particles that are freely released into the air. If these aerosols contain bacterial cells or endotoxins, they will adhere to other adjacent agar plates, destroying the integrity of the test data and leading to false positive results.

5. Why is it necessary to perform a Cleanroom Recovery Test every 6 to 12 months?

The recovery test aims to assess the electromechanical capacity of the AHU/HVAC system in automatically clearing away dust particles generated during the work shift. GMP cleanroom standards stipulate that the system must be able to return the air cleanliness from an operating state to a resting state within an ideal timeframe of 15 to 20 minutes after personnel leave, ensuring the cleanroom environment is always ready for the next testing session.