Bag Air Filters for HVAC, AHU, Commercial and Industrial Applications

Bag Air Filters, also known as Pocket Filters, are widely used in HVAC systems, Air Handling Units (AHUs), commercial buildings, factories, hospitals, data centers and cleanroom air-handling systems.

The filter media is formed into multiple flexible pockets or bags, providing a large filtration area within a relatively compact frame. This design helps increase dust-holding capacity and extend service life while maintaining suitable airflow characteristics for medium- and fine-efficiency filtration.

VIETPHAT supplies Bag Air Filters in a wide range of filtration classes, dimensions, pocket lengths, pocket quantities, media types and frame materials for commercial, industrial and cleanroom applications.

What Are Bag Air Filters?

A Bag Air Filter is an extended-surface air filter made with multiple pockets of filter media attached to a supporting frame.

Air flows into the pockets and passes through the filter media while airborne particles are captured by the fibers.

Bag Air Filters are commonly used as:

• Medium Efficiency Air Filters.
• Fine Air Filters.
• Intermediate HVAC Filters.
• Pre-filters before HEPA Filters.

Are Bag Air Filters the Same as Pocket Filters?

Yes. In most HVAC applications, Bag Filter and Pocket Filter refer to the same general filter construction.

Common names include:

• Bag Air Filter.
• Bag Filter.
• Pocket Air Filter.
• Pocket Filter.
• Multi-Pocket Filter.
• HVAC Bag Filter.

However, the actual filtration efficiency depends on the filter media and tested performance, not simply on the bag or pocket construction.

Main Advantages of Bag Air Filters

• Large effective filtration area.
• High dust-holding capacity.
• Suitable for medium and fine filtration.
• Long service life in many HVAC applications.
• Good airflow distribution.
• Available in various pocket lengths.
• Can reduce dust loading on HEPA Filters.
• Suitable for large AHUs and continuous-operation systems.

How Do Bag Air Filters Work?

When air enters a Bag Air Filter, it is distributed into multiple filter pockets. Because the media surface area is much larger than the face area of the filter, the average velocity through the media can be reduced.

Airborne particles are captured as the air passes through the media.

Performance depends on:

• Filter media.
• Filtration efficiency.
• Number of pockets.
• Pocket length.
• Rated airflow.
• Pressure drop.
• Dust loading.
• Pocket geometry.
• Stitching or pocket-separation design.

Common Types of Bag Air Filters

1. Medium Efficiency Bag Filters

Medium Efficiency Bag Filters are commonly installed after Pre Air Filters or Primary Filters.

They provide better particle removal than coarse filtration and help reduce the dust load reaching downstream fine or HEPA filters.

2. Fine Bag Filters

Fine Bag Filters use higher-efficiency media to capture smaller airborne particles.

Typical applications include:

• Commercial buildings.
• Hospitals.
• Industrial facilities.
• Cleanroom pre-filtration.
• Pharmaceutical facilities.
• Electronics manufacturing.

3. Synthetic Bag Filters

Synthetic Bag Filters use synthetic fiber media and are widely used in commercial and industrial HVAC systems.

They can provide a practical balance of efficiency, dust-holding capacity, durability and pressure drop.

4. Glass Fiber Bag Filters

Glass Fiber Bag Filters use glass fiber media in selected applications requiring specific filtration performance.

The correct media should be selected according to project requirements and operating conditions.

5. High-Capacity Bag Filters

High-Capacity Bag Filters use longer pockets, increased media area or optimized pocket construction to increase dust-holding capacity.

They are particularly useful for:

• High-dust environments.
• Large AHUs.
• Systems operating many hours per day.
• Facilities seeking longer filter replacement intervals.

Bag Air Filter Types by Application

Filter Type	Main Function	Typical Application
Medium Bag Filter	Intermediate particle filtration	AHU, HVAC
Fine Bag Filter	Fine particle filtration	Hospitals, cleanrooms
Synthetic Bag Filter	General HVAC filtration	Commercial and industrial systems
Glass Fiber Bag Filter	Higher-efficiency filtration	Special HVAC applications
High-Capacity Bag Filter	High dust-holding capacity	Factories, large AHUs

Bag Air Filters for HVAC Systems

Bag Air Filters are among the most widely used filters in commercial and industrial HVAC systems.

A typical multi-stage filtration arrangement may include:

• Stage 1: Pre Air Filter or Panel Filter.
• Stage 2: Bag Air Filter.
• Stage 3: HEPA Filter when required.

This arrangement helps reduce particulate loading on expensive downstream filters and supports stable HVAC operation.

Bag Air Filters for AHUs

Air Handling Units are one of the primary applications for Bag Air Filters.

Bag Filters are commonly installed after coarse pre-filtration and before final high-efficiency filters.

Important selection parameters include:

• Width × Height.
• Frame depth.
• Number of pockets.
• Pocket length.
• Rated airflow.
• Filter efficiency.
• Initial pressure drop.
• Recommended final pressure drop.
• Dust-holding capacity.

Bag Air Filters for Commercial Buildings

Commercial buildings often use Bag Filters in central AHUs to improve particle removal and support better indoor air quality.

Typical applications include:

• Office towers.
• Hotels.
• Shopping centers.
• Retail facilities.
• Schools.
• Airports.
• Public buildings.

Bag Air Filters for Industrial Facilities

Industrial facilities often operate HVAC systems for long periods and may experience higher dust loads than commercial buildings.

Bag Air Filters are commonly used in:

• Electronics factories.
• Semiconductor facilities.
• Pharmaceutical plants.
• Food processing facilities.
• Automotive manufacturing.
• Medical device production.
• General industrial plants.
• Warehouses and logistics centers.

Bag Air Filters for Hospitals

Hospitals frequently use multi-stage filtration systems. Bag Air Filters may be installed as medium or fine filtration stages before HEPA filters in selected HVAC systems.

The final filter configuration should follow the design and technical requirements of each hospital area.

Bag Air Filters for Cleanrooms

In cleanroom HVAC systems, Bag Air Filters are commonly used upstream of HEPA or ULPA filters.

A typical filtration sequence may include:

• Primary Air Filter.
• Bag Air Filter.
• Fine Air Filter.
• HEPA Filter.
• ULPA Filter where required.

Effective upstream filtration can significantly reduce dust loading on expensive high-efficiency final filters.

Bag Air Filters for Pharmaceutical Facilities

Pharmaceutical HVAC systems often use multiple filtration stages to support controlled manufacturing environments.

Bag Air Filters can be installed before HEPA filters to reduce particulate loading and extend final-filter service life.

Bag Air Filters for Electronics Manufacturing

Electronics manufacturing can be sensitive to dust contamination. Bag Air Filters are commonly used in AHUs serving:

• PCB manufacturing.
• Electronic component assembly.
• Display manufacturing.
• Battery production.
• Precision electronics facilities.

Bag Air Filters for Semiconductor Facilities

Semiconductor facilities often use multi-stage filtration systems with Bag Filters upstream of HEPA or ULPA filtration.

The objective is to reduce the particle load reaching high-efficiency final filters and support longer service life.

Bag Air Filters for Food Processing

Food and beverage facilities may use Bag Air Filters in HVAC systems serving production, processing and packaging areas.

The required efficiency should be selected according to process requirements, facility standards and downstream filtration.

Bag Air Filters for Data Centers

Data centers rely on continuously operating cooling and ventilation systems. Bag Air Filters can provide high dust-holding capacity and effective particle filtration.

However, pressure drop should be carefully considered because fan energy consumption can represent a significant part of operating cost.

Bag Air Filters and ISO 16890

ISO 16890 is widely used to classify general ventilation air filters according to particulate matter removal performance.

Depending on tested performance, Bag Air Filters may be classified within categories such as:

• ePM10.
• ePM2.5.
• ePM1.

The actual ISO 16890 classification depends on test results, not simply on the bag construction.

Bag Air Filters and Former EN 779 Classes

Older specifications may still refer to:

• M5.
• M6.
• F7.
• F8.
• F9.

These were classifications under the former EN 779 system.

For current projects, ISO 16890 test data should generally be preferred where available.

M5 Bag Air Filters

M5 Bag Filters were commonly used as medium-efficiency filters under the former EN 779 system.

They are widely applied in AHUs as an intermediate filtration stage.

M6 Bag Air Filters

M6 Bag Filters represented a higher medium-efficiency level under the former EN 779 classification.

They were often used where greater particulate control was needed before fine filtration.

F7 Bag Air Filters

F7 Bag Filters were widely used as fine filters under the former EN 779 system.

Typical applications include:

• Commercial buildings.
• Hospitals.
• Factories.
• Cleanroom pre-filtration.

F8 Bag Air Filters

F8 Bag Filters provided a higher filtration level than F7 under the former EN 779 standard.

They were frequently used in higher-grade HVAC applications and upstream of HEPA filters.

F9 Bag Air Filters

F9 Bag Filters represented one of the higher fine-filter classes under the former EN 779 system.

They can be used in high-grade general ventilation systems and as pre-filtration before HEPA Filters.

Bag Air Filters vs Pocket Air Filters

In general HVAC terminology, Bag Air Filters and Pocket Air Filters refer to the same filter construction.

The main difference is usually terminology rather than product design.

Bag Air Filters vs Panel Air Filters

Criteria	Bag Air Filter	Panel Air Filter
Construction	Multiple flexible bags or pockets	Flat or pleated panel
Media Area	Large	Low to moderate
Dust-Holding Capacity	Generally higher	Generally lower
Installation Depth	Deeper	Shallower
Typical Stage	Medium/fine filtration	Primary/pre-filtration

Bag Air Filters vs Pleated Air Filters

Criteria	Bag Air Filter	Pleated Air Filter
Media Configuration	Flexible pockets	Rigid or semi-rigid pleats
Installation Depth	Usually deeper	Usually more compact
Media Area	High	High depending on pleat design
Typical Application	Medium/fine filtration	Primary to fine filtration

Bag Air Filters vs HEPA Filters

Bag Air Filters do not replace HEPA Filters.

Bag Filters are general ventilation filters used primarily for medium or fine filtration, while HEPA Filters provide much higher particulate filtration performance for applications requiring strict particle control.

Bag Filters are often installed before HEPA Filters to:

• Reduce dust loading.
• Extend HEPA service life.
• Reduce HEPA replacement frequency.
• Support stable system operation.

Why Pocket Length Matters

Pocket length directly influences the amount of filter media that can be installed within the filter.

Longer pockets may provide more filtration area and greater dust-holding capacity, but they also require sufficient installation space.

Common pocket lengths may include:

• 300 mm.
• 380 mm.
• 450 mm.
• 500 mm.
• 600 mm.
• Other custom lengths.

Why the Number of Bags Matters

The number of bags influences airflow distribution and total media area.

Common configurations include:

• 3 bags.
• 4 bags.
• 5 bags.
• 6 bags.
• 8 bags.
• Other custom configurations.

More bags do not automatically mean better performance. The correct configuration depends on filter size, airflow, efficiency and pocket geometry.

Pressure Drop of Bag Air Filters

Pressure Drop is one of the most important parameters when selecting Bag Air Filters.

The large media area can help provide practical pressure-drop characteristics, but the actual resistance depends on:

• Filter efficiency.
• Media type.
• Number of pockets.
• Pocket length.
• Airflow.
• Dust loading.

As dust accumulates, pressure drop increases and may result in:

• Reduced airflow.
• Higher fan load.
• Higher energy consumption.
• Reduced HVAC performance.

Dust-Holding Capacity of Bag Air Filters

Bag Air Filters are well known for their relatively large effective media area.

This can support high Dust-Holding Capacity and longer service life when the filter is properly designed and operated.

Important Bag Air Filter Specifications

Parameter	Description
Dimensions	Width × Height × Frame Depth
Number of Bags	Number of filter pockets
Pocket Length	Length of each bag
Filtration Efficiency	According to ISO 16890 or applicable standard
Rated Airflow	Design airflow through the filter
Initial Pressure Drop	Resistance when the filter is new
Final Pressure Drop	Recommended service or replacement limit
Dust-Holding Capacity	Dust retention capability
Frame Material	Galvanized steel, aluminum or plastic

Bag Air Filter Media

Common media options include:

• Synthetic fiber media.
• Glass fiber media.
• Nonwoven synthetic media.
• Multi-layer filter media.
• Low-pressure-drop media.

The media should be selected according to filtration performance, dust loading, airflow and operating conditions.

Bag Air Filter Frame Materials

Common frame materials include:

• Galvanized steel.
• Aluminum.
• Plastic.

Frame selection should consider mechanical strength, humidity, corrosion risk and project requirements.

Custom Size Bag Air Filters

Many AHUs use filter dimensions and pocket configurations that are specific to the equipment or original manufacturer.

VIETPHAT supports Bag Air Filters according to customer requirements including:

• Width.
• Height.
• Frame depth.
• Pocket length.
• Number of bags.
• Filtration efficiency.
• Rated airflow.
• Media type.
• Frame material.
• Required quantity.

How to Select Bag Air Filters

1. Determine the Required Filtration Stage

Identify whether the Bag Filter will serve as a medium filter, fine filter or pre-filter before HEPA filtration.

2. Determine the Required Efficiency

Filter efficiency should be selected according to indoor air-quality goals, process requirements and downstream filtration.

3. Verify Filter Dimensions

Measure the filter frame dimensions and available installation depth accurately.

4. Select the Pocket Length

Longer pockets provide more media area but require more space inside the AHU.

5. Determine the Number of Bags

The correct number should be based on face dimensions, airflow, media design and target pressure drop.

6. Check Rated Airflow

The filter should operate within its recommended airflow range.

7. Evaluate Pressure Drop

The fan must have enough available static pressure to overcome the resistance of the complete filtration system.

When Should Bag Air Filters Be Replaced?

Replacement should be based on actual operating conditions rather than only on a fixed schedule.

Replacement should be considered when:

• Pressure drop reaches the specified maintenance limit.
• Airflow decreases significantly.
• The filter bags become heavily loaded.
• The media is torn or damaged.
• Bags collapse and cannot maintain proper airflow.
• The frame is damaged or distorted.
• The filter reaches the maintenance interval defined by the facility SOP.

Can Bag Air Filters Be Washed?

Most Bag Air Filters are designed as disposable filters and should not be washed.

Improper washing may:

• Damage filter fibers.
• Change filtration efficiency.
• Damage pocket seams.
• Distort the bag structure.
• Reduce filter performance.

Only products specifically designed and approved as washable should be cleaned and reused.

Life-Cycle Cost of Bag Air Filters

The initial purchase price is only one part of the total operating cost.

Life-cycle considerations include:

• Initial pressure drop.
• Average operating pressure drop.
• Dust-holding capacity.
• Filter service life.
• Replacement frequency.
• Maintenance labor.
• Fan energy consumption.
• Impact on downstream HEPA filter life.

Bag Air Filter Supplier in Vietnam – VIETPHAT

VIETPHAT supplies Bag Air Filters for HVAC systems, AHUs, commercial buildings, factories, hospitals, data centers and cleanrooms.

We support product selection based on dimensions, filtration efficiency, airflow, pressure drop, number of bags, pocket length, media type and actual operating conditions.

VIETPHAT Bag Air Filter Product Range

• Medium Efficiency Bag Filters.
• Fine Bag Filters.
• M5 Bag Filters.
• M6 Bag Filters.
• F7 Bag Filters.
• F8 Bag Filters.
• F9 Bag Filters.
• Synthetic Bag Filters.
• Glass Fiber Bag Filters.
• High-Capacity Bag Filters.
• Bag Filters for AHUs.
• Bag Filters for HVAC systems.
• Custom Size Bag Air Filters.

Applications of VIETPHAT Bag Air Filters

• HVAC systems.
• Air Handling Units.
• Fresh Air Units.
• Commercial buildings.
• Hotels.
• Shopping centers.
• Hospitals.
• Data centers.
• Electronics factories.
• Semiconductor facilities.
• Pharmaceutical plants.
• Food processing plants.
• Industrial factories.
• Cleanrooms.

Frequently Asked Questions About Bag Air Filters

What Is a Bag Air Filter?

A Bag Air Filter is an extended-surface HVAC filter consisting of multiple filter pockets or bags designed to provide a large filtration area and good dust-holding capacity.

Is a Bag Air Filter the Same as a Pocket Filter?

Yes. In most HVAC applications, Bag Filter and Pocket Filter refer to the same general multi-pocket filter construction.

What Is the Main Advantage of a Bag Filter?

Its large effective media area can provide high dust-holding capacity and long service life while maintaining practical pressure-drop characteristics.

Are M5, M6, F7, F8 and F9 Bag Filters?

They can be. These are former EN 779 filter classes, while Bag Filter describes the physical construction. Actual classification depends on tested media performance.

Can Bag Air Filters Be Installed Before HEPA Filters?

Yes. Bag Filters are commonly installed before HEPA Filters to reduce dust loading and extend final-filter service life.

How Many Bags Should a Filter Have?

The correct number depends on filter size, rated airflow, efficiency, media and pocket geometry. More bags do not automatically guarantee better performance.

What Pocket Length Should Be Selected?

Pocket length should be selected according to available installation space, airflow, desired media area, dust loading and pressure-drop requirements.

Can Bag Air Filters Be Manufactured in Custom Sizes?

Yes. Bag Filters can often be supplied with custom dimensions, pocket lengths and pocket quantities to match existing AHUs.

What Information Is Required for a Bag Air Filter Quotation?

Please provide Width × Height, frame depth, pocket length, number of bags, filtration class, rated airflow if available, media type, frame material, quantity and application.

Contact VIETPHAT for Bag Air Filters

For consultation or quotation for Bag Air Filters for HVAC, AHU, commercial, industrial and cleanroom applications, please contact VIETPHAT:

• Zalo / Hotline: 0971 344 344
• Sales: 0827 077 078
• Sales: 0829 077 078
• Email: sales@vietphat.com
• Website: www.vietphat.com