Introduction

Vantsteri engineers were invited to a pharmaceutical manufacturing facility after suspicious microorganisms were detected during routine environmental monitoring.

Upon arrival, the warehouse manager quickly led the engineering team to the warehouse area. The facility featured a modern automated three-dimensional storage system, with high-rise shelving, organized material placement, clear identification labels, and AGV vehicles moving between storage locations under computer-controlled automation.

Through a dedicated access route, the team entered the weighing and sampling room.

According to the warehouse manager, the quality control department had recently detected a suspicious microorganism during routine environmental sampling. The same suspicious microorganism was also found during raw material sampling. After genetic sequencing, both isolates were identified as the same microbial species.

If the issue could not be resolved quickly, the facility would face a potential production shutdown. Since the company was in its peak sales season, the economic impact could be significant.

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Site Inspection

The affected area was approximately 40 square meters and included:

• Personnel access routes
• Material transfer routes
• Two weighing and sampling rooms

The engineering team conducted an on-site inspection to evaluate the room structure, airflow design, contamination risk points, and possible cross-contamination routes.

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Characteristics of the Weighing and Sampling Room

A weighing and sampling room is a specialized controlled environment used for material sampling, weighing, and analysis. Its main purpose is to prevent dust and particulate matter generated during operations from spreading outside the working area.

This type of room helps protect operators from inhaling powders or materials being handled, while also maintaining a controlled and clean working environment.

The air supply system generally includes:

• Primary filters
• Medium-efficiency filters
• Centrifugal fan pressurization
• Static pressure chamber
• HEPA filtration
• Uniform airflow distribution across the working area

Clean air passes through the work zone at a controlled face velocity, forming a high-cleanliness operating environment.

The operating area of the weighing and sampling room is usually maintained under negative pressure. Approximately 10% of the circulating air is exhausted, while the air in the central weighing chamber is recirculated through a three-stage filtration system.

The HEPA filtration system can remove 99.99% of particles equal to or larger than 0.3 μm, reducing airborne dust and particulate contamination within the working area.

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Key Challenges

1. Disinfection of the Weighing Booth

The weighing booth is a critical component of the sampling room.

Because the booth is used for weighing multiple types of materials, it carries a higher risk of cross-contamination. Cleaning and disinfecting the air duct and filtration system of the weighing booth was therefore a key part of this disinfection project.

If the internal airflow system is not properly cleaned and disinfected, microorganisms may remain in ducts, filters, or hidden surfaces, creating a risk of repeated contamination.

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2. Isolation from the Warehouse Environment

The weighing and sampling room was located inside the warehouse. This created an additional challenge: contamination in the warehouse environment could potentially affect the sampling room.

During the disinfection process, the fresh air and exhaust air systems had to be handled carefully. When necessary, temporary ventilation devices were required to prevent recontamination and ensure the effectiveness of the disinfection treatment.

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Disinfection Strategy and Key Considerations

1. Identification of the Contamination Source

The first step was to confirm the microbial species detected during environmental monitoring and determine the outbreak point.

The investigation focused on whether the microorganism originated from:

• The surrounding environment
• Personnel movement
• Raw materials
• The weighing booth system
• Air supply or exhaust pathways

Based on the biological characteristics of the detected microorganism, the disinfection concentration and contact time were determined.

At confirmed outbreak points, the disinfection dosage was adjusted appropriately. Areas with potential contamination risk were also inspected and treated with preventive disinfection when necessary.

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2. Special Air Supply and Exhaust Design

Because the sampling room was located inside the warehouse, both the fresh air intake and the exhaust air were connected to the warehouse environment.

This design can reduce energy consumption, but once microbial contamination occurs, it becomes more difficult to eliminate the source and prevent recurrence.

Before disinfection, Vantsteri engineers installed temporary air supply and exhaust connections. Both the temporary air intake and exhaust discharge were directed outdoors to reduce the risk of air recirculation and cross-contamination during treatment.

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3. Secondary Treatment of the Weighing Booth

The weighing booth required separate treatment.

The booth was opened, and its air ducts and filters were cleaned. After cleaning, a dedicated Vaporized Hydrogen Peroxide (VHP) disinfection process was carried out for the weighing booth system.

This step was essential because the internal airflow pathway of the weighing booth could serve as a hidden reservoir for microorganisms if not properly treated.

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4. Disinfection of the Weighing and Sampling Room

The entire weighing and sampling room was treated using VHP decontamination.

A customized disinfection protocol was developed according to the biological characteristics of the contaminating microorganism and the contamination distribution observed on site.

For the HVAC system, the ducts were cleaned first, followed by VHP treatment of the duct space to reduce microbial contamination inside the airflow system.

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Results

After two rounds of disinfection treatment, the contamination issue in the sampling room was successfully resolved.

Follow-up monitoring showed that the suspicious microorganism was no longer detected in either environmental samples or raw material samples.

During the maintenance season the following year, the pharmaceutical manufacturer followed Vantsteri engineers’ recommendations and modified the fresh air intake and exhaust outlet design of the sampling room.

Since then, the facility has continued to invite Vantsteri engineers every year to perform comprehensive environmental disinfection and maintenance for its workshops and warehouse areas.

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Key Takeaways

This case demonstrates that contamination control in pharmaceutical weighing and sampling rooms requires more than routine surface disinfection.

Effective remediation depends on:

• Accurate microbial identification
• Root cause investigation
• Evaluation of personnel, material, and environmental contamination routes
• Proper handling of air supply and exhaust systems
• Cleaning and disinfection of weighing booth ducts and filters
• VHP decontamination of both room space and HVAC-related areas
• Post-treatment monitoring and long-term facility improvement

By combining source investigation, ventilation system control, weighing booth disinfection, and validated VHP decontamination, pharmaceutical facilities can effectively control microbial contamination and reduce the risk of production interruption.

Conclusion

Weighing and sampling rooms are critical control points in pharmaceutical warehouses because they directly interact with raw materials and controlled production processes.

In this case, the same microorganism was detected in both the environment and raw material sampling, creating a serious contamination risk for production continuity. Through systematic investigation, temporary ventilation modification, weighing booth treatment, HVAC disinfection, and VHP decontamination, the contamination event was successfully resolved.

The case also highlights the importance of long-term environmental maintenance and proper air supply and exhaust design in pharmaceutical warehouse contamination control.