Medium Efficiency Air Filters for HVAC, AHU and Industrial Applications

Medium Efficiency Air Filters are commonly used as an intermediate filtration stage in HVAC systems, Air Handling Units (AHUs), cleanrooms and industrial air treatment systems.

Unlike Pre Air Filters, which mainly capture coarse dust, Medium Efficiency Air Filters are designed to remove smaller airborne particles and reduce the dust load reaching downstream high-efficiency filters such as HEPA and ULPA filters.

VIETPHAT supplies a wide range of Medium Efficiency Air Filters including Bag Filters, Fine Filters, Pleated Filters, Compact Filters and V-Bank Filters for commercial HVAC, industrial facilities, hospitals, data centers and cleanroom applications.

What Are Medium Efficiency Air Filters?

A Medium Efficiency Air Filter is typically installed between a primary or pre-filtration stage and a high-efficiency final filter.

A typical multi-stage air filtration system may include:

• Stage 1: Pre Filter or Primary Air Filter.
• Stage 2: Medium Efficiency Air Filter.
• Stage 3: HEPA or ULPA Filter when required.

This arrangement helps reduce particle loading on expensive final filters and can improve overall filtration system performance.

Main Functions of Medium Efficiency Air Filters

• Capture finer particles than primary filters.
• Reduce dust loading on HEPA and ULPA filters.
• Extend the service life of downstream filters.
• Protect cooling coils and HVAC equipment.
• Support improved indoor air quality.
• Reduce dust accumulation inside ductwork.
• Improve the overall performance of multi-stage filtration systems.

Common Types of Medium Efficiency Air Filters

1. Bag Filters

Bag Filters, also known as pocket filters, are among the most common medium-efficiency filtration solutions used in AHUs and HVAC systems.

The filter media is formed into multiple pockets to increase the effective filtration area and dust-holding capacity.

Typical applications include:

• Air Handling Units.
• Commercial HVAC systems.
• Industrial facilities.
• Hospitals.
• Cleanroom pre-filtration.

2. Fine Filters

Fine Filters provide a higher level of particle removal compared with coarse pre-filters and are often installed as an intermediate stage before HEPA filtration.

Depending on the design, Fine Filters may be manufactured as:

• Bag Filters.
• Pleated Filters.
• Compact Filters.
• V-Bank Filters.

3. Pleated Medium Filters

Pleated Medium Filters use folded filter media to increase the effective surface area within a compact frame.

This design can provide higher dust-holding capacity while maintaining a practical pressure drop when correctly selected for the required airflow.

4. Compact Filters

Compact Filters are designed to provide a large filtration area within a relatively compact housing.

They are commonly used in systems where installation space is limited but higher filtration performance is required.

5. V-Bank Filters

V-Bank Filters use multiple filter packs arranged in a V-shaped configuration.

This design increases the total filter media area and is suitable for high-airflow systems such as:

• Large AHUs.
• Data centers.
• Commercial buildings.
• Industrial HVAC systems.

Medium Efficiency Air Filter Types by Construction

Filter Type	Main Characteristics	Typical Application
Bag Filter	Multiple pockets and large filtration area	AHU, HVAC
Fine Filter	Captures smaller particles than pre-filters	Factories, cleanrooms
Pleated Filter	Pleated media increases filtration area	Commercial HVAC
Compact Filter	High filtration area in a compact design	Industrial HVAC
V-Bank Filter	High airflow and large media area	Data centers, large AHUs

Medium Efficiency Air Filters for HVAC Systems

In HVAC systems, Medium Efficiency Air Filters are commonly installed after pre-filters to improve particle removal before the air reaches downstream components or final filtration stages.

A typical HVAC filtration arrangement may include:

• Pre Filter.
• Medium Efficiency Filter.
• HEPA Filter when required.

Proper filter selection should consider filtration efficiency, airflow, pressure drop and fan capability.

Medium Efficiency Air Filters for AHUs

Air Handling Units are one of the most common applications for Medium Efficiency Air Filters.

The filter is usually installed after the primary filtration stage and before the final filtration stage, depending on the system design.

Important parameters include:

• Filter dimensions.
• Rated airflow.
• Filter efficiency.
• Initial pressure drop.
• Recommended final pressure drop.
• Dust-holding capacity.
• Operating temperature and humidity.

Medium Efficiency Air Filters for Cleanrooms

In cleanroom HVAC systems, Medium Efficiency Air Filters can be used to reduce the particle load reaching HEPA or ULPA filters.

A typical filtration sequence may include:

• Primary Filter.
• Medium Efficiency Filter.
• Fine Filter.
• HEPA or ULPA Filter.

Using an appropriate intermediate filtration stage can help extend the operating life of final filters and reduce replacement costs.

Medium Efficiency Air Filters for Industrial Facilities

Industrial facilities often require intermediate filtration to control airborne particles before conditioned air enters production areas.

Applications include:

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

Medium Efficiency Air Filters for Commercial Buildings

Office buildings, hotels, shopping centers and other commercial facilities may use Bag Filters or Fine Filters in AHUs to improve filtration performance and support better indoor air quality.

Medium Efficiency Air Filters for Hospitals

In hospitals, medium-efficiency filters are often installed between pre-filters and final high-efficiency filtration stages.

The actual filter configuration should be selected according to the HVAC design, room classification and applicable technical requirements.

Medium Efficiency Air Filters for Data Centers

Data centers rely on continuously operating cooling and ventilation systems. Medium Efficiency Air Filters can help reduce airborne dust before it reaches sensitive equipment and cooling components.

Pressure drop is particularly important in these applications because excessive filter resistance can increase fan energy consumption.

Medium Efficiency Air Filters and ISO 16890

ISO 16890 is widely used to classify general ventilation air filters according to their performance against different particulate matter size ranges.

Filter groups include:

• ISO Coarse.
• ePM10.
• ePM2.5.
• ePM1.

Medium Efficiency Air Filters may fall within different ISO 16890 categories depending on the actual tested performance of the filter.

Medium Efficiency Filters and EN 779

Older technical specifications may still reference filter classes such as M5, M6, F7, F8 and F9 under the former EN 779 classification system.

For new projects, ISO 16890 data should be preferred when available.

Direct conversion between old EN 779 classes and ISO 16890 categories should not be made without supporting test data.

What Is an M5 Air Filter?

M5 was a medium-efficiency filter class under the former EN 779 standard.

M5 filters were commonly supplied as Bag Filters, Panel Filters or Pleated Filters and used as an intermediate stage in HVAC and AHU systems.

Medium Efficiency Air Filters vs Fine Air Filters

Criteria	Medium Efficiency Air Filter	Fine Air Filter
Typical Position	Intermediate stage	Intermediate or near-final stage
Filtration Level	Medium	Higher depending on configuration
Applications	AHU, HVAC, industrial facilities	Cleanrooms, hospitals, high-grade HVAC
Main Purpose	Reduce downstream dust loading	Capture finer particles and protect HEPA filters

Medium Efficiency Air Filters vs Pre Air Filters

Pre Air Filters mainly capture coarse particles, while Medium Efficiency Air Filters are designed to remove smaller airborne particles.

Both filtration stages are often used together in multi-stage HVAC systems.

Medium Efficiency Air Filters vs HEPA Filters

Medium Efficiency Air Filters do not replace HEPA Filters.

HEPA Filters provide a much higher level of particulate filtration and are commonly used as final-stage filters in applications requiring strict particle control.

Installing medium-efficiency filtration before HEPA can help:

• Reduce dust loading.
• Extend HEPA filter life.
• Reduce HEPA replacement frequency.
• Improve system operating stability.

Pressure Drop of Medium Efficiency Air Filters

Pressure Drop is a key technical parameter when selecting a medium-efficiency filter.

Because the filter media is generally denser than coarse pre-filter media, pressure drop is typically higher than that of a primary filter.

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

• Reduced airflow.
• Higher fan load.
• Higher energy consumption.
• Changes in HVAC system balance.

Dust-Holding Capacity

Dust-Holding Capacity describes the amount of dust a filter can retain under specified test conditions before reaching a defined operating limit.

Bag Filters and V-Bank Filters often provide a relatively large media area, which can support higher dust-holding capacity depending on the product design.

Important Technical Parameters

Parameter	Description
Dimensions	Width × Height × Depth
Filter Class	Based on ISO 16890 or the applicable standard
Rated Airflow	Air volume passing through the filter
Initial Pressure Drop	Resistance when the filter is new
Final Pressure Drop	Recommended operating or replacement limit
Dust-Holding Capacity	Dust retention capability
Filter Media	Affects efficiency, resistance and service life
Frame Material	Aluminum, galvanized steel, plastic or other materials

Custom Size Medium Efficiency Air Filters

AHUs and industrial HVAC systems may use different filter dimensions depending on equipment design.

VIETPHAT supports Medium Efficiency Air Filters according to customer requirements such as:

• Width.
• Height.
• Depth.
• Number of pockets for Bag Filters.
• Pocket length.
• Filter efficiency.
• Rated airflow.
• Frame material.
• Required quantity.

How to Select Medium Efficiency Air Filters

1. Determine the Filtration Stage

Identify whether the filter will be installed after a Pre Filter, before a HEPA Filter, or as the final filtration stage in a general HVAC system.

2. Determine the Required Efficiency

The filter efficiency should match the indoor air quality target, process requirement and HVAC design.

3. Check Rated Airflow

The filter should operate within its designed airflow range to avoid excessive resistance and reduced service life.

4. Check Pressure Drop

The fan must have sufficient available static pressure to overcome the total resistance of the filtration system.

5. Consider Dust-Holding Capacity

For high-dust environments, filters with adequate media area and dust-holding capacity should be considered.

When Should Medium Efficiency Air Filters Be Replaced?

Replacement should be based on actual system conditions rather than only on a fixed number of months.

Consider replacement when:

• Pressure drop reaches the specified limit.
• Airflow decreases significantly.
• Filter media becomes heavily loaded.
• Filter pockets are damaged or collapsed.
• The frame becomes distorted.
• The filter reaches the maintenance interval defined by the facility SOP.

Can Medium Efficiency Air Filters Be Washed?

Most Bag Filters, Fine Filters and Compact Filters are designed as disposable filters and should not be washed or reused.

Improper cleaning may damage the filter media and change its filtration performance.

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

Life-Cycle Cost of Medium Efficiency Air Filters

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

Important life-cycle factors include:

• Initial pressure drop.
• Average operating pressure drop.
• Service life.
• Dust-holding capacity.
• Replacement frequency.
• Labor cost.
• Fan energy consumption.
• Ability to extend HEPA filter service life.

Medium Efficiency Air Filter Supplier in Vietnam – VIETPHAT

VIETPHAT supplies Medium Efficiency Air Filters for HVAC systems, AHUs, commercial buildings, industrial facilities, hospitals, data centers and cleanrooms.

We support filter selection based on size, airflow, filtration efficiency, pressure drop, filter construction and actual operating conditions.

Medium Efficiency Air Filter Product Range

• Bag Filters.
• M5 Bag Filters.
• Medium Pleated Filters.
• Fine Filters.
• Compact Filters.
• V-Bank Filters.
• Medium Filters for AHUs.
• Medium Filters for HVAC systems.
• Custom Size Medium Efficiency Air Filters.

Applications

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

Frequently Asked Questions About Medium Efficiency Air Filters

What is a Medium Efficiency Air Filter?

A Medium Efficiency Air Filter is an intermediate-stage air filter typically installed after a pre-filter and before a HEPA or other high-efficiency final filter.

Is a Medium Efficiency Air Filter the same as a Fine Filter?

The terms may overlap depending on the manufacturer and classification system. The actual tested efficiency and technical specification should be used instead of relying on the product name alone.

Is M5 a Medium Efficiency Filter?

M5 was classified as a medium-efficiency filter under the former EN 779 standard. For new projects, ISO 16890 test data should be used when available.

Is a Bag Filter a Medium Efficiency Air Filter?

It can be. Bag Filter describes the construction, while the actual filtration efficiency depends on the filter media and tested performance.

Should a Medium Filter Be Installed Before a HEPA Filter?

In many HVAC and cleanroom systems, yes. A medium or fine filter can reduce dust loading and extend HEPA filter service life.

Can Medium Efficiency Air Filters Be Manufactured in Custom Sizes?

Yes. Bag Filters, Pleated Filters and other configurations can often be supplied according to existing AHU dimensions and technical requirements.

What Information Is Required for a Quotation?

Please provide the filter type, Width × Height × Depth, filtration class, rated airflow if available, number and length of pockets for Bag Filters, quantity and application.

Contact VIETPHAT for Medium Efficiency Air Filters

For consultation or quotation for Medium Efficiency Air Filters for HVAC, AHU, industrial facilities 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