F7 F8 F9 Box Filter for AHU and Commercial Air Handling
The F7 F8 F9 box filter is designed for the intermediate filtration stage in HVAC and air handling systems. It is used when a system needs better particle removal than a basic pre-filter, but does not require a HEPA final filter.
This filter is commonly installed after a primary filter and before sensitive downstream equipment, compact filters or HEPA filters. It helps reduce fine dust loading, protect the air handling unit, and improve the overall stability of multi-stage filtration systems.
For contractors, facility engineers and system integrators, this product is usually selected by efficiency grade, airflow, pressure drop, installation space and replacement size. ZOSLONG can supply standard and custom box filters according to existing AHU filter lists, old filter samples or project drawings.
Send Inquiry
Please send us the filter size, required grade, airflow, quantity and application. We can help check whether this box filter is suitable for your AHU or ventilation project.
Where This Filter Fits in the HVAC System
A box filter is normally used as a stronger filtration stage after the coarse pre-filter.
A typical filtration arrangement may be:
Coarse pre-filter → F7/F8/F9 box filter → compact filter or HEPA filter
In this arrangement, the pre-filter captures larger dust and lint, while the F7/F8/F9 box filter removes finer particles before the air reaches more sensitive downstream stages.
This helps reduce dust loading on higher-efficiency filters and can make maintenance more predictable in commercial and industrial HVAC systems.
This product is not a replacement for HEPA filters in cleanroom terminal applications. If the project requires H13, H14 or ULPA filtration, a HEPA or ULPA filter should be selected instead.
Certifications
Our Sub-high efficiency filter is certified with CE and ISO standards, ensuring compliance with international quality and safety regulations. This certification guarantees that our products meet the highest standards of performance and reliability.
F7 F8 F9 Selection Guide
F7, F8 and F9 are commonly used as legacy project references for medium-to-high efficiency HVAC filters. For new international projects, ISO 16890 test data may also be required. These classification systems are not exact one-to-one equivalents, so the final selection should be confirmed according to the selected media and available test data.
| Grade Reference | Typical Use Direction | Selection Notes |
|---|---|---|
| F7 | Intermediate filtration in general commercial HVAC systems | Often used where better air quality is needed after the coarse pre-filter |
| F8 | Higher intermediate filtration for more demanding ventilation systems | Suitable when the project requires stronger fine dust control |
| F9 | High-end medium filtration before compact or HEPA stages | Often selected for sensitive HVAC systems or upstream protection |
| ISO 16890 Option | International projects requiring ePM data | Available according to selected media and test data |
If your tender document specifies ISO ePM1, ISO ePM2.5 or ISO ePM10 performance, please send the requirement before quotation. We can help match the filter media and provide available test information according to the project specification.
Who usually buys this kind of filter
The people sending enquiries for a product like this are usually working from a real project, a real replacement need, or a real maintenance problem.
It is often:
a contractor upgrading an AHU stage
an equipment supplier matching a project specification
a distributor serving repeat commercial demand
a maintenance buyer replacing an existing mid-stage filter
an OEM that needs a stable box-filter format for standard air-handling applications
These buyers are usually less interested in slogans than in whether the filter suits the stage they are trying to build.
That is why this page should feel more like a practical conversation than a generic product brochure.
Construction and Material Options
The box filter structure provides a larger filter area than a flat panel filter. This helps support higher airflow, better dust holding capacity and more stable pressure drop during service.
Filter Media
The media can be selected according to the required efficiency grade, airflow and pressure drop target. Synthetic media and glass fiber media are commonly used for medium-to-high efficiency HVAC filtration. The final media choice should be based on project requirements and available test data.
Frame Options
Frame material can be selected according to installation environment, strength requirement and budget.
| Frame Option | Typical Use |
|---|---|
| Galvanized steel frame | Industrial and commercial AHU systems |
| Aluminum frame | Lightweight HVAC applications and corrosion-sensitive environments |
| Plastic frame | Selected projects requiring lightweight structure |
| Custom frame | Replacement projects with special installation tracks |
Sealing and Support
Depending on the installation method, the filter can be supplied with gasket, handle, protective mesh, airflow direction label or customer item code label.
Why Choose a Box Filter Instead of a Flat Panel Filter?
A flat panel filter is usually used as a coarse or primary filter. It is suitable for capturing larger particles and protecting the first stage of the system.
A box filter is selected when the system needs:
•Higher filtration efficiency
•Larger filter area
•Better dust holding capacity
•More stable pressure drop
•Stronger structure for AHU installation
•A suitable intermediate stage before compact or HEPA filters
For systems with limited installation depth, the box filter depth and structure should be checked carefully before replacement.
Quality Control and Documentation
ZOSLONG operates under an ISO 9001 quality management system. For F7 F8 F9 box filters, we focus on dimensional accuracy, frame strength, media fitting, sealing condition and packing quality.
Typical inspection items include:
•Outer dimensions
•Frame straightness
•Media and pleat condition
•Frame sealing and bonding
•Gasket position, if required
•Airflow direction label
•Quantity and carton information
•Packing condition before shipment
For project orders, we can provide specification sheets, packing lists, label files and available test data according to the selected media and project requirements.
If CE-related documents, ISO 16890 test data, RoHS/REACH statements, MSDS or third-party testing are required, please confirm the applicable product scope before ordering.
Packing and shipping
FAQ
Q: How often do I need to replace the filter?
A: The filter life depends on the specific application and environmental conditions. Generally, filters should be replaced every 6-12 months or when the pressure drop increases significantly.
Q: Can the filter remove viruses?
A: Our Box Air Filter is designed to reduce bacteria and protozoan cysts but is not specifically rated for virus removal. For virus protection, consider additional filtration methods.
Q: Is the filter easy to clean?
A: Yes, the filter is easy to clean and maintain. It can be easily backwashed to extend its life.
Q: Where is the filter made?
A: Our filters are made in our state-of-the-art facility, ensuring high-quality standards.
Q: Can I use the filter in high particulate environments?
A: The filter is designed for general use. For high particulate environments, additional pre-filtration may be required to protect the filter.
Information Needed for Quotation
To quote correctly, please provide the following information:
•Filter size: width × height × depth
•Required grade: F7, F8, F9 or ISO 16890 reference
•Quantity for each size
•Airflow or face velocity, if available
•Initial pressure drop requirement, if specified
•Frame material requirement
•Gasket or sealing requirement
•Application: AHU, commercial ventilation, pre-HEPA stage or other
•Whether it is a new project or replacement project
•Photos, drawings or existing filter list
•Destination country and preferred shipping term
If the old filter is available, you can send us photos of the label, frame, gasket and installation track. This helps us confirm the replacement size and structure more accurately.
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