In a pharmaceutical factory’s clean production system, transferring materials, equipment, or samples between areas of different clean grades is a key weak point in pollution prevention and control. Direct transmission through the door is likely to cause air convection between clean and non-clean areas, or between high- and low-level clean areas. This may lead to cross-contamination of particulate matter and microorganisms, violating the core GMP requirement of “preventing contamination and cross-contamination.” As a device designed to address cross-regional pollution transmission, the transfer window—with its precise structural design and functions—serves as an “invisible barrier” to ensure production quality. This article will analyze its application advantages in pollution prevention, production efficiency, and compliance management.
Core Advantage One: Blocking air convection to prevent cross-contamination from the source
Cross-contamination is a major quality risk in pharmaceutical production. Air exchange during cross-regional transmission is the main route for such contamination. The transfer window uses a double-door interlocking system and internal purification to block the pollution chain. This achieves both physical isolation and active purification—its core application value. (1) The double-door interlock delivers physical isolation.
The core structure of the transfer window is designed in such a way that “the two side doors cannot be opened simultaneously”. The state of the door is strictly controlled by mechanical locks or electronic interlocking devices: when one side of the door is opened, the other side of the door is forcibly locked and cannot be opened. Only when the open door is completely closed and sealed can the other side door be unlocked. This design fundamentally avoids direct air circulation between the clean area and the external area.
Take the material transfer in the “general area → D-level clean area” of the solid dosage form workshop as an example: If the transfer window is not used and the two connecting doors are directly opened, air convection will be formed instantly. Dust in the general area (the concentration of suspended particles with a diameter of ≥0.5μm can reach more than 10⁶ per cubic meter) will directly flood into the D-level clean area (the standard requirement is ≤ 352,000 per cubic meter), causing the cleanliness of the clean area to exceed the standard instantly. When the materials are transferred through the transfer window, they first enter the transfer window, and the side door of the general area is closed. After the door is sealed, they are taken out through the side door of the clean area. The entire process has no direct air exchange, which can reduce the contamination risk of cross-area transfer by more than 99%.
(2) Internal purification and enhanced pollution removal
In addition to physical isolation, the mainstream transfer Windows are all equipped with active purification systems to further remove contaminants adhering to the surface of the transferred materials. According to the cleanliness level requirements, purification systems can be classified into three categories:
Ultraviolet disinfection type: Equipped with an internal ultraviolet sterilization lamp, it irradiates the transferred equipment, packaging materials, etc., with ultraviolet light for 15 to 30 minutes, killing over 90% of the bacteria, fungi, and other microorganisms on the surface. It is suitable for material transfer in D-level clean areas.
High-efficiency filtration (HEPA) supply air type: Clean air is delivered into the transfer window through an internal HEPA filter (filtration efficiency ≥99.97%@0.3μm), creating a slight positive pressure. At the same time, the internally contaminated air is discharged through the return air outlet for filtration. It is suitable for the transfer of materials and samples in C-class and B-class clean areas.
Sterile air shower type: On the basis of HEPA filtration, A high-pressure air shower device is added to perform 360° blowing on the surface of the material to remove adhering dust particles. It is suitable for the core material transfer in sterile preparation workshops (with an A-level background).
The actual measurement data of a certain cephalosporin sterile preparation enterprise shows that after adopting the sterile air shower type transfer window, the microbial residue on the material surface has decreased from the original ≤5CFU/piece to ≤1CFU/piece, and the dust residue has decreased from ≤10mg/piece to ≤0.5mg/piece, completely eliminating the pollution risk of cross-regional transfer.
Second, Core Advantage Two: Optimize the transmission process and enhance production and operation efficiency
In pharmaceutical production, the transfer of materials and equipment involves the collaboration of multiple departments (such as warehousing, production, and quality inspection). Traditional transfer methods require manual door opening and multiple cleaning and disinfection processes, which are cumbersome and time-consuming. The transfer window, through standardized and automated design, has significantly optimized the transfer process, reducing labor and time costs.
(1) Simplify the transmission process and reduce manual intervention
The traditional transfer process is as follows: materials arrive at the entrance of the area → Notify the recipient → The recipient wears clean suits and arrives at the entrance → both parties hand over → the recipient takes the materials back to the clean area for cleaning → the materials are put into use. The entire process requires the cooperation of 2 to 3 people and takes 15 to 20 minutes.
After using the transfer window, the process is simplified to: The materials are placed in the transfer window → the outer door is closed → the purification system is turned on → the receiving party is notified through the walkie-talkie or indicator light → After the receiving party confirms the purification is completed, the inner door is opened to take the materials. Only one person is needed to operate, the time is shortened to 3-5 minutes, the labor cost is reduced by more than 60%, and at the same time, the additional pollution risk caused by frequent cross-area movement of personnel is avoided.
(2) Adapt to various transmission requirements and enhance scene compatibility
The transfer window can be customized and designed according to the different transfer requirements of pharmaceutical factories, adapting to various scenarios.
Customized by size: From small reagent sample transfer Windows (volume ≤50L) to large equipment spare parts transfer Windows (volume ≥1000L), it can meet the transfer requirements of materials of different specifications.
Material compatibility: For corrosive materials (such as acid and alkali reagents), 316L stainless steel material is adopted. For sterile materials, the inner wall mirror polishing process (roughness Ra≤0.8μm) is adopted, which is convenient for cleaning and sterilization.
By function expansion: It can integrate functions such as temperature and humidity monitoring, material traceability scanning, and automatic log recording and transmission, meeting the management requirements of intelligent workshops.
For instance, a certain traditional Chinese medicine extraction workshop adopts a custom-made large transfer window, which can directly transfer the filter elements of the extraction tank with a diameter of 1.2 meters without disassembling the filter elements. This avoids material loss and contamination during the disassembly process. Each transfer can save 40 minutes of filter element assembly time and increase production efficiency by an average of 15% per day.
Iii. Core Advantage Three: Compliant with regulatory requirements and a complete quality traceability system
GMP has clear requirements for the “traceability” and “process controllability” of pharmaceutical production. The transfer window is not only a pollution control device but also the “hardware support” for the compliance of the quality system. Its design and operation data can directly meet the requirements of regulatory audits.
(1) The hardware design complies with GMP standards
The structural design of the transfer window strictly adheres to the requirements of GMP for clean equipment:
The shell and inner wall are made of stainless steel, with no dead corners or cracks, which is convenient for cleaning and disinfection.
The door body is equipped with silicone rubber sealing rings, which have excellent sealing performance (leakage rate ≤0.5%).
The electrical components are equipped with explosion-proof and dust-proof functions, meeting the safety requirements of clean areas.
The key components of the purification system, such as filters and ultraviolet lamps, have clear model numbers and replacement records, which can be traced back to their sources.
In GMP on-site audits, the compliance of transfer Windows is one of the key inspection items. A compliant design of transfer Windows can directly prevent audit deficiencies caused by “loss of control in the transfer process”.
(2) Traceable operation data supports quality control
Modern transfer Windows are generally equipped with data recording functions, which can automatically record the time of each transfer, the operator, purification parameters (such as ultraviolet irradiation time, air shower duration), temperature, and humidity. The data can be stored for ≥1 year and support USB export or connection to the workshop MES system.
This traceability not only meets the GMP requirements for “process documentation” but also enables the rapid identification of potential risks in the transfer process when quality issues arise. For instance, a tablet manufacturer found that the microbial content exceeded the standard during the finished product inspection. By tracing the operation log of the transfer window, it was discovered that the ultraviolet lamp was not properly turned on during the transfer of a certain batch of materials. The cause of contamination was promptly identified, thus avoiding a wider product recall.
Four. Core Advantage Four: Reduce maintenance costs in clean areas and extend the service life of equipment
The maintenance cost of the clean area (such as the replacement of high-efficiency filters, cleaning and disinfection consumables, and energy consumption) is one of the main operating costs of a pharmaceutical factory. The transfer window reduces the maintenance pressure in the clean area indirectly by minimizing the intrusion of external contaminants and prolonging the service life of the core purification equipment.
(1) Reduce the air purification load in the clean area
The high-efficiency air filter (HEPA) in the clean area is the core purification equipment, and its service life is directly related to the concentration of pollutants entering the clean area. The air convection caused by the traditional transfer method will allow a large amount of external pollutants to enter the clean area, accelerating the clogging of the HEPA.
The operation data of a certain D-level cleanroom shows that when the transfer window is not in use, the replacement cycle of HEPA is 6 to 8 months, with an annual replacement cost of approximately 300,000 yuan. After using the HEPA air supply type transfer window, the replacement cycle of HEPA has been extended to 12-15 months, the annual replacement cost has dropped to 150,000 yuan, and the maintenance cost has decreased by 50%.
(2) Reduce the frequency of cleaning and disinfection and the consumption of consumables
The invasion of external contaminants will increase the frequency of cleaning and disinfection in clean areas (such as floor wiping and space fumigation). After the use of the transfer Windows, the dust concentration and microbial concentration in the clean area have been significantly reduced. The cleaning frequency can be reduced from twice a day to once a day, and the consumption of disinfection consumables (such as alcohol and disinfectants) has been reduced by more than 40%, further lowering the operating costs.
V. Conclusion
As a “tiny but crucial” device in the clean production system of pharmaceutical factories, the value of the transfer window is not only reflected in its basic function of “physical isolation”, but also in its multi-dimensional empowerment of pollution prevention and control, efficiency improvement, compliance guarantee and cost optimization, which builds a “full-chain quality defense line” for cross-regional transmission. Against the backdrop of the pharmaceutical industry’s increasing emphasis on quality compliance and efficiency improvement, choosing a transfer window that suits the scene requirements and establishing a standardized usage and maintenance system have become an inevitable choice for pharmaceutical enterprises to ensure drug quality and reduce operating costs.
In the future, with the development of intelligent manufacturing technology, transfer Windows will further integrate with the Internet of Things and big data to achieve full-process intelligence of “automatic material identification – intelligent purification initiation – automatic data upload – automatic abnormal alarm”, providing more solid hardware support for the high-quality development of the pharmaceutical industry.
