In the process of drug production, air cleanliness is directly related to the purity, stability, and safety of drugs, and is one of the core elements to ensure the quality of drug production. Medium-efficiency air filters, as a crucial component of the air purification system in pharmaceutical factories, play an irreplaceable role in multiple scenarios, such as pretreatment, terminal protection, and local purification, due to their highly efficient interception capacity for particles of specific sizes. This builds a solid air quality defense line for pharmaceutical production.
I. The Core Role of Medium-Efficiency Air Filters in Pharmaceutical Factories
The filtration efficiency of medium-efficiency air filters lies between that of primary and high-efficiency filters. They mainly intercept suspended particles ranging from 1 to 10 μm, such as dust, pollen, microbial spores, and certain aerosols. Their core functions are reflected in three dimensions:
Protect key downstream equipment. As the “pre-guard” of high-efficiency air filters (HEPA), medium-efficiency filters can pre-filter out most of the larger particles in the air, significantly reducing the load on high-efficiency filters, preventing them from clogging prematurely, and extending the service life of high-efficiency filters (usually by 3 to 5 times), while also lowering replacement costs and the frequency of downtime for maintenance. Ensure the continuous and stable operation of the purification system.
Controlling particulate pollution in the production environment: In scenarios such as the transition areas between clean and non-clean zones and auxiliary production areas in pharmaceutical factories, medium-efficiency filters can directly achieve initial air purification, controlling the concentration of suspended particles in the air within a certain range, laying the foundation for subsequent high-efficiency purification processes and reducing the risk of particulate pollution to raw materials, semi-finished products, and finished products of drugs.
Auxiliary maintenance of pressure difference balance in clean areas: The stable operation of the air filtration system is the key to maintaining the pressure difference in different clean level areas of the pharmaceutical factory. The medium-efficiency filter, through a reasonable resistance design and in combination with the system fan, can help regulate the intake and exhaust air volumes of each area, ensuring that the clean area maintains positive pressure (or negative pressure) compared to the non-clean area and the high-clean-level area compared to the low-clean-level area, such as in a biosafety laboratory, and preventing cross-contamination caused by air backflow.
Having outlined the fundamental functions, we now turn to specific applications of medium-efficiency air filters based on the production scenarios found within pharmaceutical factories.
This is the most fundamental and core application scenario for medium-efficiency filters. In the centralized air purification system of a pharmaceutical factory, the air first passes through a primary filter (intercepting particles larger than 5μm), and then enters a medium-efficiency filter for secondary filtration. This stage mainly processes the air after the mixture of outdoor fresh air and return air, removing most of the dust, fibers and other impurities to prevent these pollutants from entering the interior of downstream equipment such as surface coolers, heaters and humidifiers, which may cause scaling, corrosion or microbial growth of the equipment, thereby affecting the air treatment effect and the service life of the system.
Typical application areas: All fresh air handling units in production workshops, laboratories, storage areas, etc. that rely on centralized air conditioning and purification systems.
(2) Transition areas between clean zones and non-clean zones
In transitional areas such as personnel passages and material transfer passages in pharmaceutical factories, air turbulence is prone to form, causing pollutants from non-clean areas to spread into clean areas. Medium-efficiency air filters are often used in conjunction with air curtain machines and local supply air outlets to form an “air barrier” in the transition area. For instance, before personnel enter the clean area, they need to pass through an air shower room. The supply air outlets of the air shower room are usually equipped with medium-efficiency filters to ensure that the air blown towards personnel has removed most of the particles, preventing the dust carried by personnel from entering the clean core area. Medium-efficiency filters will also be installed inside the material transfer window to prevent the materials from being contaminated by air pollutants during the transfer process.
Typical application areas: air shower rooms, buffer rooms, material transfer Windows, and the connection areas between clean corridors and ordinary corridors.
(3) End-of-pipe purification in medium-clean production areas
For some production areas with medium cleanliness level requirements (such as the crushing and screening workshops for solid dosage forms, where the cleanliness level is usually Class D), medium-efficiency filters can be directly used as terminal purification equipment. Although the requirements for air particles in such areas are lower than those in aseptic preparation workshops (A/B grade), the concentration of particulate matter still needs to be controlled to prevent drugs from absorbing moisture, caking, or being contaminated by microorganisms. The medium-efficiency filter evenly supplies air through the ceiling supply air outlet or side supply air outlet, and in combination with the return air outlet, forms a circulation purification to control the concentration of suspended particles in the area within the D-level clean standard range (the number of particles greater than or equal to 0.5μm per cubic meter does not exceed 3,520,000).
Typical application areas: solid dosage form workshops, storage and preparation areas for pharmaceutical excipients, and refining workshops for non-sterile active pharmaceutical ingredients.
(4) Air purification in auxiliary production areas
Although the auxiliary areas of a pharmaceutical factory, such as laboratories, office buildings, and staff restrooms, do not directly participate in drug production, pollutants in the air may indirectly affect production quality through personnel movement, ventilation systems, etc. Medium-efficiency filters can be used at the end of the air conditioning systems in these areas to improve indoor air quality, reduce the impact of dust, pollen, etc. on the accuracy of experimental instruments, and at the same time provide employees with a comfortable working environment, indirectly ensuring production efficiency.
Typical application areas: Quality inspection laboratories (non-sterile inspection areas), administrative office buildings, staff changing rooms, and rest rooms.
Iii. Key Points for Selection and Maintenance of Medium-Efficiency Air Filters
To fully leverage the role of medium-efficiency air filters in pharmaceutical factories, it is necessary to strictly control the selection, installation, and maintenance processes to ensure that they precisely match the production demands.
(1) Scientific selection: Match the cleanliness requirements with the system characteristics
Selection of filtration efficiency: Choose a filter with an appropriate efficiency level based on the cleanliness requirements of the application scenario. The commonly used efficiency grades of medium-efficiency filters include G4 (EN779 standard) and F5-F9 (EN779 standard). Among them, G4 grade is suitable for the pretreatment section, F5-F7 grade is suitable for the transition area and auxiliary production area, and F8-F9 grade can be used for the end purification of the medium-cleanliness level production area. For instance, it is recommended that F7 grade be selected for the pretreatment section in the aseptic preparation workshop to better protect the downstream high-efficiency filters. For the end of the solid dosage form Class D workshop, Class F8 can be selected.
Resistance characteristic matching: The initial resistance of the filter should be compatible with the air pressure of the fan in the air purification system to avoid insufficient air volume in the system due to excessive resistance or incomplete filtration due to insufficient resistance. Generally, the initial resistance of medium-efficiency filters should be controlled between 50 and 150Pa, and attention should be paid to the variation curve of resistance with the increase of dust holding capacity. Products with a gentle increase in resistance should be selected.
Material compatibility: In some areas of the pharmaceutical factory, there are high temperatures, high humidity, or corrosive gases (such as solvent evaporation during the production of active pharmaceutical ingredients), so filter materials that are resistant to temperature, humidity, and corrosion should be selected. For instance, filter paper can be made of glass fiber or synthetic fiber (such as polyester fiber), the frame can be made of galvanized steel plate or aluminum alloy, and the sealant should be a non-toxic and non-volatile product that meets the standards of the pharmaceutical industry.
(2) Standardized maintenance: Ensure the continuous and stable filtration efficiency
Regular monitoring and replacement: Establish a filter maintenance ledger and regularly (usually every 3 to 6 months) check the resistance changes of medium-efficiency filters. When the resistance reaches twice the initial resistance, it must be replaced in a timely manner to avoid a decrease in system air volume due to excessive resistance or secondary pollution caused by contaminants penetrating the filter.
Clean control during the replacement process: When replacing medium-efficiency filters in the clean area, the replacement area should be disinfected in advance. Operators should wear clean suits, gloves, and masks to avoid introducing new contaminants during the replacement process. The replaced waste filters should be sealed and packaged and disposed of in accordance with the regulations for hazardous waste treatment to prevent the spread of pollutants within them.
System interlocking inspection: After replacing the filter, it is necessary to check the sealing condition between the filter and the frame (the smoke emission method can be used for detection) to ensure there is no air leakage. After the system is started and running for 30 minutes simultaneously, the cleanliness indicators in the detection area (such as the number of suspended particles and the concentration of microorganisms) should be checked. Only after confirming that they meet the production requirements can production be resumed.
Iv. Application Value and Development Trends
The application of medium-efficiency air filters in pharmaceutical factories not only directly ensures the air cleanliness during the drug production process, but also reduces the nonconformity rate of drugs caused by particulate contamination, and helps pharmaceutical enterprises meet the strict requirements for the production environment stipulated in the Good Manufacturing Practice (GMP) for drugs, providing key support for the quality and safety of drugs.
With the continuous improvement of the cleanliness requirements in the pharmaceutical industry, medium-efficiency air filters are developing towards higher efficiency, lower resistance, and longer service life. For instance, medium-efficiency filters that adopt the new type of composite fiber filter material can reduce the initial resistance by more than 20% while maintaining an F8 filtration efficiency. Filter materials with antibacterial functions can inhibit the growth of microorganisms on the surface of the filter, further enhancing the purification effect. In the future, medium-efficiency air filters will be deeply integrated with intelligent air purification systems. By using built-in sensors to monitor filtration efficiency in real time, they can be replaced as needed and maintained intelligently, providing more precise and efficient guarantees for the quality of drug production in pharmaceutical factories.
