1. Filtration Efficiency & Leak Test Standard (Fundamental Quality Baseline)

Efficiency class shall be defined per EN 1822, covering H13 and H14. Verbal claims of “Class 100” from suppliers shall not be taken as the sole criterion.

• H13: ≥99.95% overall efficiency for MPPS (Most Penetrating Particle Size)

• H14: ≥99.995% overall efficiency for MPPS

H14 is preferred for high-risk areas including GMP aseptic workshops, semiconductor fabs and weighing room exhaust.

Mandatory requirement for qualified products: Individual PAO scan leak test for every unit, rather than sampling inspection. Leakage hotspots of separated HEPA filters are commonly located at the bonding joints between filter media and separators, glue sealing interfaces between media and frames, and gaps of sealing gaskets. Inferior filters only undergo sampling checks. Micro-leakage may remain at separator bonding gaps, leading to out-of-limit particle levels on site after installation, which are difficult to troubleshoot.

Verification tips: Request individual PAO leak test reports delivered together with goods. Scan records shall cover the full filter surface, separator seams and peripheral sealing edges. Avoid products that only provide batch type test certificates without unit-level leak records.

2. Filter Media Area & Rated Airflow (Determine Filtration Velocity & Service Life)

For separated HEPA filters with identical outer frame size and thickness, pleat pitch and separator spacing vary among manufacturers, resulting in large discrepancies in total filter media area — an indicator easily overlooked. Filter media area directly governs filtration velocity. Lower filtration velocity delivers stable filtration performance, slower pressure drop build-up and higher dust holding capacity.

Reliable suppliers clearly state the total unfolded media area and rated airflow, instead of only listing outline dimensions. For conventional glass fiber media, the recommended operating filtration velocity is 0.03～0.06 m/s. Actual operating airflow is suggested to stay within 70%~85% of the rated airflow; continuous full-load operation is not recommended.

Selection tips: Under the same airflow rate, filters with larger media area perform better. Premium products feature uniform separator spacing and sufficient pleats, without cutting pleat counts to reduce raw material cost. Exercise caution if the supplier only provides outline dimensions without media area data.

3. Initial Resistance, Final Resistance & Resistance Curve (Match Fan System Design)

Initial resistance means the pressure loss of a new filter under rated airflow. For H13 separated HEPA filters with aluminum foil separators and glass fiber media, the reasonable initial resistance range is 220～280 Pa; H14 models have slightly higher resistance. A lower resistance value does not always represent better quality. Abnormally low resistance usually comes from reduced media area and excessive filtration velocity. It shows favorable pressure performance at the initial stage, yet pressure will surge rapidly after dust accumulation and shorten service life.

Qualified suppliers provide complete resistance rise curves and clearly specify the recommended final resistance value. Normally, the final resistance is set at approximately twice the initial resistance, serving as the threshold for differential pressure alarm and filter replacement. Inferior products only offer a single initial resistance reading without dust loading curves, leaving no reference for later operation and maintenance. This may cause clogged filters, airflow decline, and substandard air velocity for air showers or laminar flow hoods.

During selection, fan pressure margin shall be calculated comprehensively based on initial resistance plus final resistance, rather than only the initial resistance of new filters.

4. Separator Material, Frame & Structural Rigidity (Adapt to Working Conditions, Prevent Deformation & Air Leakage)

As the skeleton of separated HEPA filters, separators directly determine temperature resistance, moisture tolerance and negative pressure resistance:

• Aluminum foil separator: High rigidity, stable flow channel, moderate moisture resistance; the first choice for most clean air supply and exhaust systems

• Paper separator: Low cost, sensitive to moisture, prone to swelling and debonding in humid environments; prohibited for exhaust, high-humidity and frequently cleaned areas

• Plastic separator: Resistant to weak acid and weak alkali corrosion, suitable for process exhaust with trace chemical vapors for AMC control

Frame materials include aluminum alloy, galvanized steel and stainless steel. Stainless steel frames are preferred for negative pressure exhaust, high-humidity and corrosive environments; aluminum alloy is sufficient for ordinary air supply applications.

For high-quality products, separators are firmly bonded without virtual bonding or debris shedding, resisting deformation under continuous negative pressure impact. Inferior aluminum foil separators are thin with sparse bonding points. Repeated negative pressure impact will loosen separators and collapse filter media, triggering internal leakage.

Sealing gaskets also require verification. Silicone and EPDM are widely used. For semiconductor AMC control projects, silicone-free sealing formulations must be specified to avoid product contamination caused by siloxane precipitation.

5. Sealing Structure & Installation Adaptability (Eliminate Bypass Leakage)

Even premium filter media will lose clean performance once sealing fails. There are two mainstream sealing types: compression sealing and liquid tank sealing.

• Compression sealing: Rely on evenly distributed pressure plates to compress sealing gaskets. High-quality gaskets are continuous with uniform elasticity, paired with flat, non-warping frames. Diagonal locking during installation is applicable to laminar flow hoods, air shower tunnels and standard air outlets.

• Liquid tank sealing: Adopted for high-grade cleanroom ceiling terminals and systems that cannot be shut down frequently. Premium liquid tank frames feature high flatness and uniform immersion depth, preventing overhead fitting or partial separation from sealing gel.

Identification tips: Low-cost products have thin frames prone to warping, with gaps at gasket joints. Partial air leakage may occur after compression, triggering continuous alarms at frame edges during PAO leak tests. Qualified filters go through frame flatness inspection before delivery, equipped with integrated sealing parts and fewer joints.

Supplementary Verification Points

• Filter media: Ultrafine glass fiber media is preferred. Distinguish glass fiber media from PP media; PP media has low temperature resistance and shall not be used in high-temperature conditions.

• Temperature resistance: Conventional aluminum foil separated glass fiber filters allow continuous operation ≤80℃. Special high-temperature models are required for high-temperature scenarios.

• Dust holding capacity: Larger filter media area brings higher dust holding capacity and longer replacement cycles, ideal for exhaust stations with heavy dust load.

• Delivery documents: Besides PAO reports, request airflow-resistance test reports and material certificates (separator, sealing, filter media).

Quick Pitfall-Avoidance Summary

Many purchasers only compare outline dimensions and unit price while ignoring the above five indicators, and end up buying products with identical appearance but degraded performance. The hallmarks of qualified separated HEPA filters: individual PAO leak test, sufficient filter media area, complete resistance curve, separator and frame matched to working conditions, and reliable sealing solution.

Bacclean H13/H14 separated HEPA filters adopt aluminum foil separators and glass fiber filter media. Customization for compression sealing, liquid tank sealing and silicone-free sealing is supported. Each filter is delivered with PAO leak test and airflow-resistance test reports, suitable for cleanroom air supply, laminar flow hoods, air shower tunnels, negative pressure weighing room exhaust and other applications.