How to ensure that the microbial content in the air meets gmp requirements?

In order to ensure that the microbial content in the air meets GMP (Good Manufacturing Practice) requirements, a comprehensive prevention and control system needs to be built from multiple dimensions such as air purification system design, operation maintenance, monitoring and verification, and personnel management. The following are specific measures:

1. Air purification system design: source control microbial pollution

1. Efficient filtration system
   • primary filter: Intercept particulate matter (such as dust and hair) ≥5μm, protect the intermediate filter and extend its service life.
   • medium efficiency filter: Filter 1-5μm of particulate matter to further purify the air and reduce the attachment of microorganisms to carriers.
   • High-efficiency filter (HEPA): Filtration of particulate matter ≥0.3μm, the efficiency reaches more than 99.97%, directly intercepting bacteria, viruses and other microorganisms. GMP requires that air in critical areas (such as sterile filling areas) be HEPA filtered, and the filter installation position must conform to the direction of air flow to avoid short circuits.
   • Ultra-High Efficiency Filter (ULPA): The filtration efficiency for particulate matter ≥0.12μm reaches 99.9995%, suitable for Class A clean areas (such as cell culture and sterile preparation production).
2. Air flow organization and differential pressure control
   • One-way flow (laminar flow): Vertical or horizontal one-way flow is used in the Class A area, with an air flow speed of 0.36-0.54m/s to ensure that pollutants are continuously discharged and avoid cross pollution.
   • Non-unidirectional flow (turbulent flow): Used in level B, C, and D areas, the air can form a vortex by reasonably arranging the air supply and return ports to dilute the microbial concentration.
   • pressure gradient: Maintain a pressure difference of ≥ 10Pa between clean and non-clean areas to prevent the invasion of external microorganisms. For example, the pressure difference between the sterile filling area and the adjacent room needs to be ≥12.5Pa, and the pressure difference meter needs to be calibrated regularly.
3. climate control
   • temperatureThe temperature in the clean area is usually controlled at 18-26℃ to avoid high temperature causing accelerated microbial reproduction or uncomfortable operation.
   • humidity: Relative humidity control at 45%-65%, to prevent excessive humidity breeding mold (such as Aspergillus, Penicillium), or humidity is too low to cause static accumulation (may adsorb microorganisms).

II. Operation and maintenance of air purification equipment: guarantee continuous purification ability

1. Replace the filter regularly
   • primary filter: Replace every 3-6 months, or replace when the pressure difference reaches 2 times the initial value.
   • medium efficiency filter: Replace every 6-12 months, or replace when the pressure difference reaches 2 times the initial value.
   • high efficiency filter: Replace it every 1-3 years, or replace it when the air volume detected by the air volume meter drops to 70% of the initial value. Integrity testing (such as DOP/PAO testing) is required before replacement to ensure no leaks.
2. Cleaning and disinfection of air conditioning systems
   • Surface air cooler, heater: Wipe and disinfect with 0.1% bromogeramine or 75% ethanol every quarter to prevent the growth of mold.
   • duct system: Clean the inner wall once a year and use a special vacuum cleaner or high-pressure air to purge to prevent dust accumulation from becoming a breeding ground for microorganisms.
   • Air supply outlet, air return outlet: Clean once a month to remove dust and microbial attachments.
3. Ozone or ultraviolet disinfection
   • ozone disinfection: In the unmanned state, use an ozone generator to disinfect the air and surfaces. The concentration must be ≥20mg/m³ and the action time should be ≥30 minutes. Ventilation is required after disinfection to ensure that ozone residue is ≤0.1mg/m³.
   • ultraviolet disinfection: Install an ultraviolet lamp in the return air outlet or air conditioner box with a wavelength of 254nm and an intensity of ≥70μW/cm². Irradiation for ≥30 minutes a day to kill microorganisms in the air.

3. Microbial monitoring and verification: quantitative evaluation of purification effect

1. dynamic monitoring
   • settling bacteria method: Place nutrient agar petri dishes in critical areas (such as level A area), incubate for 48 hours after 30 minutes of exposure, and count the number of colonies (CFU). The standard for Level A area is ≤ 1 CFU/dish, and Level B area is ≤ 5 CFU/dish.
   • Microplankton method: Collect air samples using a plankton sampler (such as Anderson sampler), and count the number of colonies after incubation. The standard for Level A area is ≤1CFU/m³, and Level B area is ≤10CFU/m³.
   • particle counter: Monitoring the number of particulate matter ≥0.5μm and ≥5μm indirectly reflects the risk of microbial contamination. The dynamic standard for Class A area is ≥0.5μm particles ≤3520 pieces/m³, and ≥5μm particles ≤20 pieces/m³.
2. periodic verification
   • Air conditioning system verification: Including installation qualification (IQ), operation qualification (OQ), performance qualification (PQ), verifying whether temperature, humidity, pressure difference, wind speed and other parameters meet the design requirements.
   • filter integrity test: Use DOP/PAO to test the penetration rate of the high-efficiency filter to ensure that it is ≤0.01%.
   • Verification of disinfection effect: Verify that the killing rate of ozone or ultraviolet disinfection is ≥99.9% through microbial challenge tests (such as using Bacillus subtilis spores).

4. Personnel and materials management: reducing the risk of man-made pollution

1. Personnel hygiene control
   • gowning procedure: Personnel entering the clean area must follow the process of “changing shoes → changing clothes → washing hands → disinfecting → drying hands → wearing clean clothes → wearing masks and gloves” to ensure aseptic operation.
   • Code of Conduct: It is prohibited to walk quickly, speak loudly or cough in the clean area to reduce the spread of microorganisms.
   • training assessment: Regularly train employees on microbial pollution control, and can only take up their posts after passing the assessment.
2. Material purification process
   • material delivery: Transfer materials through airlock spaces or transfer windows. The transfer windows must be equipped with ultraviolet lamps or laminar flow devices to ensure that microorganisms on the surface of the materials are killed.
   • sterilization processing: Carry out moist heat sterilization (121℃, 15 minutes) or dry heat sterilization (180℃, 2 hours) on materials (such as containers and stoppers) that are in direct contact with drugs to ensure sterility.

V. Emergency response and continuous improvement

1. deviation handling
   • If monitoring finds that microorganisms exceed the standard, production needs to be stopped immediately, the cause (such as filter leakage, abnormal pressure differential, personnel operation violations, etc.), and corrective measures (such as replacing filters, strengthening disinfection, and re-training personnel) must be taken to resume production.
2. continuous improvement
   • Regularly review microbial monitoring data, analyze trends, and optimize air purification system parameters (such as adjusting air volume and replacing more efficient filters).
   • Pay attention to industry trends and introduce new technologies (such as new antibacterial coatings, intelligent monitoring systems) to improve the level of microbial control.