What This Product Is (and where it belongs in a filter train)
A pocket filter (also called a pleated bag filter) is a medium-efficiency HVAC filter commonly used in:
Second-stage filtration after a prefilter
Primary filtration in cleaner commercial AHUs (depending on IAQ targets)
It's designed to handle continuous airflow with stable shape and predictable loading.
Standards & Ratings:
Specs depend on region and tender language. Many modern projects reference ISO 16890. Older documents still reference EN 779 (F-class).
We support both ways of writing the requirement:
EN 779 legacy: F5 / F6 / F7 / F8 / F9 (as required in legacy specs)
For procurement, the most important line items are always the same:
Initial Resistance at your design airflow
Recommended final resistance (changeout point)
Size and depth compatibility with your AHU rack
Two Build Paths: Standard vs Deep-Pocket (Choose based on service interval)
We manufacture both configurations because different sites have different priorities.
Standard Pocket Filters (6 or 8 pockets)
Best for commercial AHUs where access is routine and budgets prefer standard service intervals.
Why contractors specify it
Reliable, widely used configuration
Easier handling during changeout
Good balance of cost and performance
Typical fit
Office buildings, malls, schools
AHUs with scheduled quarterly or seasonal maintenance
Deep-Pocket Filters (Extended Life)
Built for longer service intervals or higher dust loading where changeouts are disruptive or expensive.
Why facility teams choose it
More media area for better dust holding
Helps slow down ΔP rise when loading is heavy
Can reduce emergency changeouts in long-runtime systems
Typical fit
Buildings with extended operating hours
Locations with persistent outdoor dust loading
Sites where filter access is difficult or labor cost is high
Quick Selection Table (the version procurement can approve)
| Your Site Reality | Best Starting Option | Notes |
|---|---|---|
| Routine access, standard runtime, moderate dust | Standard 6/8 pocket | Simple, cost-stable choice |
| Long runtime, heavy loading, changeouts are disruptive | Deep-pocket extended life | More media area helps stabilize service interval |
| Downstream filters are expensive (V-bank, HEPA stage, etc.) | Deep-pocket + strong prefilter | Protects the whole filter train |
| Uneven loading or bypass history | Add gasket + check rack sealing |
Sealing fixes save more money than media upgrades
|
Construction Details That Decide Real Performance
Our engineers often see early failures caused by shortcuts that don't show up in a datasheet. Here's what we control as a manufacturer.
Filter Media
Synthetic nonwoven HVAC media options (selected by required class and service interval)
Configurations tuned for lower initial resistance or higher dust holding, depending on project priority
Pocket Design & Support
Reinforced pocket seams to reduce tearing under airflow
Pocket spacing that helps reduce pocket-to-pocket contact
Optional support choices for higher face velocities or demanding duty
Frame (Header) Options
Galvanized steel header (common commercial standard)
Aluminum header option (weight/corrosion considerations depending on environment)
Optional gasket (recommended when bypass is common or rack condition varies)
Pressure Drop: What to Specify so you don't get surprises
Pressure drop is where filter selection becomes operational cost.
When comparing suppliers, request these three items at your airflow:
Initial Resistance (clean filter ΔP)
Recommended final resistance (changeout ΔP)
Suggested face velocity range (or airflow range per size)
If you're replacing an existing pocket filter, send:
The current filter size and pocket depth
Your measured ΔP (if available)
Operating schedule (hours/day)
That one email often prevents under-sizing.
RFQ Checklist (Copy/Paste)
To quote correctly-standard or deep-pocket-send:
Filter size (W × H × header depth) + quantity
Required standard language: ISO 16890 or EN 779 legacy class
Airflow (CFM/m³h) or face velocity
Preferred option: Standard 6/8 pockets or Deep-pocket extended life (or "recommend")
Frame material preference + gasket requirement
Site notes: coastal humidity, heavy dust loading, maintenance interval
If available: measured current Pressure Drop across the filter bank
We reply with a matched configuration, a project-ready quote, and a supply plan.
Factory-Direct Support (Why it matters on multi-site contracts)
Buying direct from the source factory changes the parts that create delays:
Consistent build across batches
OEM/ODM labeling and packaging for contractors/distributors
Stable lead times with fewer handoffs
Documentation support aligned to tender language
ZOSLONG manufactures HVAC filters since 1997 and supports export projects for the US, Europe, and Southeast Asia.
Typical Specification Fields (Project-Friendly)
Below are the fields procurement teams use to lock down like-for-like replacement and avoid ambiguity:
Size (W × H × header depth): custom to match existing racks
Pocket count: standard 6 pockets / 8 pockets, plus deep-pocket options
Pocket depth: standard or deep-pocket (based on service interval)
Frame/header material: GI / aluminum
Gasket: yes/no; location requirement
Media class: ISO 16890 class or EN 779 legacy class (as required)
Initial resistance: stated at design airflow
Final resistance: recommended changeout point
Qty and delivery plan: project-based batching supported
About Our Company
Founded in 1997, we're a vertically integrated filtration manufacturer with 20+ patents and a 6,500㎡ plant combining automated pleating, ultrasonic bonding, metal fabrication, PU potting, and final assembly. Our in-house lab verifies pressure drop, efficiency, dust-holding capacity, leakage, and dimensions from incoming materials to final packaging under an ISO 9001 quality system with full IQC/IPQC/FQC traceability.
We supply primary/coarse panels, pleated HVAC/furnace filters, pocket (bag) filters, rigid V-bank modules, aluminum-frame panels, media filter boxes, plus industrial dust-collection elements (cartridges/pleated bag filters). Media options span synthetic microfiber, fiberglass, activated carbon, nanofiber, PTFE, and high-temperature blends with anti-static, flame-retardant, hydrophobic finishes. Services include OEM/ODM, custom sizes/grades (ISO 16890 / MERV), private labeling, and compliance documentation (ASHRAE 52.2 / ISO 16890, RoHS/CE). With predictable lead times, global logistics (express/air/sea; EXW/FOB/CIF/DAP/DDP), and responsive after-sales support (installation guidance, maintenance recommendations, 24-hour response), we help customers in commercial buildings, healthcare, food & beverage, electronics, paint finishing, power, and metals achieve cleaner air at lower life-cycle cost
FAQ
Q: Can pleated bag filters replace my existing bags and cages one-for-one?
A: In many pulse-jet baghouses, yes. A pleated bag filter with the correct top design and diameter will fit directly into the existing tube-sheet opening and does not require a separate cage. We confirm this using your drawings or a sample before production.
Q: How much more filter area do I get with pleated bags?
A: Depending on diameter, length and pleat geometry, it is common to see about 2–3× the media area compared with a traditional felt bag of the same diameter. Some designs can reach close to 300% more area in retrofit projects.
Q: Are pleated bag filters suitable for all dust types?
A: They work very well for many dry, free-flowing dusts (cement, lime, minerals, metals, many plastics and powders). For very sticky, fibrous or highly condensable dusts, we prefer to review your process data first to decide whether a pleated bag or a conventional felt bag is more reliable.
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