Air Filter Selection for APIs Manufacturing air conditioning

Air filter class selection for zone concept of GMP for different APIs Product.


9/3/202310 min read

Filter class selection for APIs Area serving Air Handling Units:

(Active Pharmaceutical Ingredient) manufacturing areas is critical for maintaining air quality and ensuring compliance with Good Manufacturing Practices (GMP). In pharmaceutical facilities, air filters are categorized based on their efficiency in removing particulate matter. Two common filter classes used in API manufacturing areas are F9 and F10, with different zones (A, B, C, D, and F) having varying requirements. Here's a comprehensive overview of filter class selection and zoning considerations:

Filter Classes (F9 and F10):

· F9 and F10 are high-efficiency particulate air (HEPA) or ultra-low penetration air (ULPA) filters, designed to capture and remove very fine particles from the air.

· F9 filters have a minimum efficiency of 95% for particles with a size of 0.4 µm, while F10 filters have a minimum efficiency of 99.9995% for 0.1 µm particles.

· The choice between F9 and F10 depends on the specific requirements of the manufacturing process and the desired level of air quality.

Zone Concept in GMP:

In pharmaceutical manufacturing, GMP guidelines are followed to ensure the quality and safety of pharmaceutical products. These guidelines often incorporate the concept of zoning, where different areas of the facility are classified based on their cleanliness and the risk of contamination. The most commonly used zones in GMP facilities are:

1. Zone A: This is the critical zone where the actual API manufacturing or processing takes place. The air quality in Zone A is of utmost importance to prevent contamination of the product. In this zone, F10 filters are typically recommended to achieve the highest level of air purity.

2. Zone B: Surrounds Zone A and serves as a transition area. It should have good air quality but not as stringent as Zone A. F9 filters may be used in Zone B to provide sufficient air cleanliness.

3. Zone C: This zone is located around Zone B and has a lower risk of contamination. F9 filters are generally suitable for this area.

4. Zone D: Zone D is outside of the production area and has the lowest cleanliness requirements. Here, regular HVAC filters (e.g., MERV 8-10) are often sufficient for air quality control.

5. Zone F: Zone F includes areas that are not directly related to production but are still within the pharmaceutical facility. These areas may require standard HVAC filters suitable for their intended purpose.

Air Bag Filters:

Bag air filters, also known as pocket filters, are commonly used in HVAC systems for air handling units. Their selection should be based on the requirements of each zone, with F9 or F10 filters being used in the more critical zones (A and B). Bag filters offer a larger surface area and can effectively capture particles, making them suitable for maintaining air quality in pharmaceutical manufacturing areas.

In conclusion, selecting the appropriate filter class (F9 or F10) and zoning concept (A, B, C, D, F) for API manufacturing areas is essential to ensure compliance with GMP and maintain the desired air quality levels in different areas of the facility. The choice of filter class should be based on the specific cleanliness requirement of each zone within the pharmaceutical manufacturing facile the packaging area is a critical part of Production process where the final pharmaceutical products are prepared for distribution. Maintaining air quality and cleanliness in the packaging area is essential to ensure the safety and integrity of the pharmaceutical products. Here is a list of filter class recommendations for different areas within the pharmaceutical packaging area, presented in an informative manner:

1. Primary Packaging Area:

· Filter Class: F9 or F10 Bag Filters

· Rationale: The primary packaging area is where pharmaceutical products come into direct contact with packaging materials. It is crucial to maintain high air quality to prevent contamination. F9 or F10 bag filters offer excellent particle removal efficiency.

2. Secondary Packaging Area:

· Filter Class: F8 or F9 Bag Filters

· Rationale: The secondary packaging area is where primary packaged pharmaceutical products are further processed, labeled, and prepared for distribution. While air quality is important, it may not require the same level of filtration as the primary packaging area, making F8 or F9 bag filters suitable.

3. Carton and Label Printing Area:

· Filter Class: F7 or F8 Bag Filters

· Rationale: This area involves printing and labeling processes, and while cleanliness is necessary, the air quality requirements may be slightly lower than in other packaging areas. F7 or F8 bag filters provide effective particle removal.

4. Corridor and Access Areas:

· Filter Class: MERV 7 or MERV 8 Bag Filters

· Rationale: Corridors and access areas do not have direct product contact and typically have lower air quality requirements compared to packaging and processing zones. MERV 7 or MERV 8 bag filters are suitable for maintaining general air quality in these spaces.

5. HVAC Systems Serving Packaging Areas:

· Filter Class: F9 or F10 Bag Filters

· Rationale: The HVAC systems supplying air to the packaging areas should use high-efficiency bag filters (F9 or F10) to ensure that the air entering these zones is free from contaminants and meets the required cleanliness standards.

6. Cleanroom for Sterile Packaging (if applicable):

· Filter Class: HEPA (High-Efficiency Particulate Air) Filters

· Rationale: In cleanrooms used for sterile packaging, HEPA filters with an efficiency of 99.97% or higher for 0.3 µm particles are necessary to maintain an ultra-clean environment and prevent microbial contamination.

It's essential to conduct a thorough risk assessment and consider the specific requirements of your pharmaceutical packaging area when selecting filter classes. Compliance with Good Manufacturing Practices (GMP) and adherence to local regulatory standards are also crucial factors in determining the appropriate filter class for each area within the packaging facility. Regular maintenance and validation of filtration systems are equally important to ensure consistent air quality and product integrity.

Filter Media:

Filter media refers to the material or medium used within a filter to trap and remove particulate matter or contaminants from the air or fluid passing through it. The choice of filter media is critical as it directly impacts the filter's efficiency and performance. Different types of filter media are used depending on the specific application and filtration requirements. Here are some common types of filter media:

1. Fibrous Media: This type of media is made from synthetic or natural fibers, such as fiberglass, cellulose, or polyester. Fibrous media is widely used in HVAC filters and can capture particles through mechanical filtration.

2. HEPA Media: High-Efficiency Particulate Air (HEPA) filters use a dense mat of fine fibers, typically fiberglass, to capture particles as small as 0.3 micrometers with high efficiency.

3. Membrane Media: Membrane filters have a thin, porous membrane made of materials like polytetrafluoroethylene (PTFE) or polypropylene. They are used in applications requiring sterile filtration.

4. Pleated Media: Pleated filters have a folded or pleated design, which increases the surface area for particle capture. They are commonly used in HVAC and air purification systems.

5. Bag Media: Bag filters utilize a bag-shaped filter medium, often made of synthetic materials, for industrial dust and particle filtration. The selection of filter media depends on factors such as the type and size of contaminants, air or fluid flow rates, filtration efficiency requirements, and the specific application.

DOP Test for HEPA Filters:

The Dispersed Oil Particulate (DOP) test is a standard test method used to evaluate the efficiency of High-Efficiency Particulate Air (HEPA) and Ultra-Low Penetration Air (ULPA) filters. It is essential for ensuring that these filters meet their efficiency specifications. Here's an overview of the DOP test procedure:

Objective: To determine the filtration efficiency of a HEPA filter by challenging it with a known aerosol of Dispersed Oil Particulate (DOP) particles.

Equipment and Materials:

1. DOP aerosol generator: Produces a stable and known concentration of DOP particles.

2. Test duct or chamber: Where the filter being tested is installed.

3. Particle counter: Measures the upstream and downstream particle counts.

4. Pressure gauges: Measure pressure differentials across the filter.

5. Flow meter: Monitors airflow through the filter.

6. Data acquisition system: Records test data.


1. Calibrate the DOP aerosol generator to produce a stable concentration of DOP particles.

2. Install the HEPA filter to be tested in the test duct or chamber.

3. Measure and record the initial pressure drop across the filter and the airflow rate.

4. Introduce the DOP aerosol into the upstream side of the filter at a controlled flow rate.

5. Continuously sample the air downstream of the filter using a particle counter.

6. Allow the test to run until a stable count of particles downstream of the filter is achieved.

7. Calculate the filtration efficiency of the HEPA filter based on the particle counts upstream and downstream of the filter.

Interpretation: The efficiency of the HEPA filter is calculated by comparing the upstream and downstream particle counts. HEPA filters are expected to have an efficiency of at least 99.97% for particles with a size of 0.3 micrometers (or 99.99% for ULPA filters). If the filter meets or exceeds these efficiency criteria, it is considered suitable for its intended application. If not, adjustments or replacements may be necessary.

The DOP test is a critical quality control measure for HEPA filters used in cleanrooms, pharmaceutical manufacturing, healthcare facilities, and other environments where high filtration efficiency is required to maintain air quality and prevent contamination.


In conclusion, filter media is the essential material within a filter that captures and removes particulate matter or contaminants from air or fluids. Different types of filter media are used depending on the specific application, with choices ranging from fibrous media and activated carbon to HEPA, membrane, pleated, and bag media. The selection of filter media depends on factors like the type and size of contaminants, filtration efficiency requirements, and application-specific needs.

The DOP test, or Dispersed Oil Particulate test, is a standard procedure used to assess the filtration efficiency of HEPA and ULPA filters. This test helps ensure that these high-efficiency filters meet their specifications for removing particles from the air. The DOP test involves challenging the filter with a known concentration of DOP particles and measuring particle counts upstream and downstream of the filter. HEPA filters are expected to have an efficiency of at least 99.97% for 0.3 micrometer particles, and the test helps verify if they meet or exceed this efficiency requirement.

Overall, both filter media selection and the DOP test are crucial elements in maintaining air quality, cleanliness, and compliance with quality standards in various industries, including pharmaceutical manufacturing, cleanrooms, and HVAC systems. Proper filter media choice and regular testing ensure that filters effectively remove contaminants and maintain the desired air quality levels in critical environments

Method of Checking Bag Filters Installed in Air Handling Units with a Manometer (Magnehelic Gauge):

A Magnehelic gauge, or simply a manometer, is a device used to measure and monitor air pressure differentials in HVAC systems. It can be used to check the condition and performance of bag filters installed in air handling units. Here's a step-by-step method for checking bag filters using a Magnehelic gauge:

Tools and Materials:

1. Magnehelic gauge (with appropriate pressure range)

2. Access to the air handling unit

3. Screwdriver or appropriate tool for removing access panels (if necessary)

4. Pen and paper for recording measurements


1. Safety Precautions:

· Ensure the air handling unit is turned off before performing any checks to prevent injury.

· Follow all safety protocols and wear appropriate personal protective equipment (PPE) if required.

2. Access the Air Handling Unit:

· Open the access panels or doors on the air handling unit to reach the bag filters. Depending on the unit's design, you may need to remove fasteners or screws.

3. Identify the Bag Filters:

· Locate the bag filters within the air handling unit. Note their position and orientation.

4. Initial Pressure Differential Measurement:

· Connect the Magnehelic gauge to two pressure taps—one placed upstream (before the filters) and the other downstream (after the filters).

· Ensure that the tubing connecting the gauge to the pressure taps is properly sealed and airtight.

5. Zero the Gauge:

· Zero the Magnehelic gauge by adjusting it to read zero when there is no pressure differential. This should be done before every measurement.

6. Turn On the Air Handling Unit:

· Start the air handling unit and allow it to run at its normal operating conditions for a sufficient duration (e.g., 15-30 minutes) to stabilize airflow.

7. Measure Pressure Differential:

· Read and record the pressure differential on the Magnehelic gauge. This reading represents the initial pressure drop across the bag filters while they are in their current condition.

8. Compare with Manufacturer's Specifications:

· Refer to the manufacturer's specifications or documentation for the bag filters to determine the acceptable pressure drop range for filters in good condition.

9. Visual Inspection:

· Visually inspect the bag filters for any visible damage, clogs, or other issues that may affect their performance.

10. Replacement or Maintenance:

· If the pressure differential exceeds the manufacturer's recommended range or if there are visible issues with the filters, it may be necessary to replace or clean them, as per your maintenance schedule and procedures.

11. Repeat Measurements (Optional):

· If you've taken corrective actions (replacing or cleaning filters), you can repeat the pressure differential measurement to confirm that the filters are now within the acceptable range.

12. Record and Document:

· Record the pressure differential readings, the date of the check, and any actions taken in a maintenance log or record sheet.

13. Close Access Panels:

· Once you've completed the checks and maintenance, securely close and seal the access panels on the air handling unit.

14. Turn Off the Air Handling Unit:

· Turn off the air handling unit to conclude the procedure.

Regular monitoring of bag filters using a Magnehelic gauge helps ensure that they are functioning efficiently, maintaining proper airflow, and not causing unnecessary energy consumption. Timely maintenance and replacement of filters when needed contribute to the overall effectiveness of HVAC systems.

How to check air pressure of manufacturing packaging area to prevent cross flow of air and cross contamination write in step by step

To check and control air pressure differentials between manufacturing and packaging areas in a pharmaceutical facility, you can follow a series of steps to prevent crossflow of air and cross-contamination. Maintaining appropriate air pressure differentials is crucial for ensuring product quality and compliance with Good Manufacturing Practices (GMP). Here's a step-by-step guide:


Maintaining proper air pressure differentials in API manufacturing is a critical aspect of ensuring product quality, preventing cross-contamination, and complying with GMP standards. By following this step-by-step procedure, pharmaceutical facilities can systematically check and control air pressure differentials at key entry/exit points. , Air locks thus enhancing the integrity of their API manufacturing processes. Additionally, thorough documentation of measurements and adjustments is vital for regulatory compliance and maintaining a high level of quality assurance.

Record keeping is responsibility of QA department and Engineering Department will do all test and maintenance According to SOP.