Why Your HEPA Filters Need EN1822 Scan Testing

EN1822 is the European standard used to classify and test EPA, HEPA, and ULPA filters. In practical purchasing terms, it helps answer three questions:

•What is the filter's efficiency at MPPS (Most Penetrating Particle Size)?

•Does the finished filter meet the required class, such as H13 or H14?

•Is there any local leak in the media pack, sealant line, or frame assembly?

This last point is where many buyers get caught.

A filter can pass an overall efficiency requirement and still have a local defect. That defect may be tiny. But in a clean environment, tiny is enough. Even a leak path representing around 0.01% of the effective area can become the dominant route for particle bypass downstream.

Overall efficiency tells you how the filter performs as a whole. Scan testing tells you whether one bad spot will compromise the whole system.

A small leak can create a big contamination problem

Cleanrooms do not fail because of average performance. They fail because of weak points.

Our engineers often see the same issue during project reviews: the buyer focuses on the filter class, but not on the integrity of the finished unit. The media may be high quality. The rating may say H13 or H14. But if there is a leak at the sealant edge or a damaged pleat, particles will pass through the easiest path.

That creates problems such as:

•Failed room qualification

•High downstream particle counts

•Rework during installation or commissioning

•Product contamination risk

•Disputes over whether the problem came from the filter or site installation

Finished-product integrity is different from raw media performance

Raw media efficiency and finished-filter performance are not the same thing.

A finished HEPA filter includes more than filter paper. It includes:

•Separator or mini-pleat structure

•Frame

•Adhesive or sealant

•Gasket or gel-seal interface

•Pleat pack bonding

•Edge treatment and assembly accuracy

A defect in any of these areas can create bypass.

That is why buyers who only ask for an "H13 certificate" are often not asking enough. For critical applications, you should also ask for finished-unit EN1822 scan test records.

Under EN1822, HEPA filters are classified by their performance at MPPS.

Quick reference: H13 vs H14

What buyers should take from this

H14 is ten times stricter than H13 in integral penetration terms.

The local penetration limit is also much tighter for H14.

Moving from H13 to H14 usually means:

•Higher filtration efficiency

•Higher quality control requirements

•Often higher pressure drop

•Usually higher cost

•So the right question is not "Is H14 better?"
The right question is: Does this project really require H14, and can the system handle the added resistance?

For many commercial and industrial clean-air projects, H13 is the correct engineering choice. For higher-risk environments, H14 may be required. Selection should always consider:

•Cleanliness target

•Air change rate

•Allowable pressure drop

•Fan capacity

•Energy consumption

•Validation requirements

Why Scan Testing Is More Important Than a Generic "Passed" Label

A simple "passed inspection" statement is not enough for serious B2B projects.

When buyers review a HEPA filter leak testing record, they should want proof that the finished filter was checked across the full face area and perimeter, not just visually inspected or batch-approved.

A reliable test approach helps you verify:

The filter class matches the specification

There are no local leaks above the acceptance limit

The pressure drop is within the expected range

The unit can be traced by serial number or batch number

If the report does not identify the individual filter, the airflow condition, and the pass/fail basis, it is weak documentation.

At ZOSLONG, for HEPA filters that require EN1822 verification, our practice is one-by-one testing, not random sampling.

1) Visual and dimensional inspection before testing

Before scan testing starts, each filter is checked for:

Frame dimensions

Media pack condition

Pleat spacing and alignment

Sealant continuity

Surface damage from handling

Gasket condition, where applicable

This step matters. A damaged pleat or corner seal is often visible before the instrument confirms it.

2) Test setup at specified airflow conditions

The filter is mounted on the test rig and checked under the specified airflow or test condition required by the product design and project requirement.

At this stage, we confirm:

Proper seating of the filter

Stable airflow across the filter face

Correct test configuration for the product type

3) Upstream aerosol challenge

A controlled aerosol is introduced upstream so penetration can be detected downstream.

This is the core of HEPA filter leak testing. The purpose is simple: if there is a weak point, the downstream probe should find it.

4) Full-face scan of the finished filter

This is where scanning matters.

Instead of assuming the filter is good because the average result is good, the downstream probe is moved across the finished unit, including:

Media surface

Pleat lines

Frame-to-media interface

Sealant edges

Corner areas

Joint transitions

Our engineers often see local defects show up in the perimeter zones first, especially if a filter has been mishandled during packing, transport, or installation preparation.

5) Pass/fail judgment against the required class

The measured result is compared against the applicable acceptance criteria for the specified class, such as H13 or H14.

If any local point exceeds the allowable limit, the filter is flagged as nonconforming.

6) Test record and traceability

Each tested unit can be linked to its report data. That gives buyers something useful for incoming inspection, project handover, and future quality review.

This is the real value of non-sampling QC: you are not guessing whether your unit came from the good part of the batch.

How to Read an EN1822 Scan Test Report

Many buyers receive a test report but do not know which numbers actually matter.

Here is what to review first.

Filter identification

The report should clearly show:

Filter model

Size

Class

Batch number or serial number

Test date

If you cannot match the report to the actual unit, the report has limited value.

Rated airflow or test condition

Pressure drop and performance data only make sense when tied to a defined airflow.

Look for:

Test airflow

Face velocity, where applicable

Product type or test setup reference

Efficiency or penetration result

This tells you whether the unit meets the class requirement.

For example:

H13: integral penetration must remain within the H13 limit

H14: integral penetration must remain within the H14 limit

Local scan result

This is one of the most important sections.

You want confirmation that:

The finished filter was scanned

The maximum local penetration remained below the allowed limit

The final result is clearly marked Pass

If the report mentions only "overall efficiency" and says nothing about scanning, that is not the same thing.

Initial resistance / Pressure Drop

This matters for system design and operating cost.

A very low pressure drop may sound attractive, but buyers should compare it against:

Filter class

Airflow

Media area

Product design

Always read resistance data in context. A claim without airflow is not useful.

Operator or equipment reference

For quality-sensitive projects, it also helps when the report includes:

Test operator or QC signoff

Equipment ID or traceable test method

Internal inspection reference

Good reports reduce arguments later.

When sourcing HEPA filters for cleanroom or critical HVAC use, ask these questions before placing the order:

Technical questions

Is the filter classified under EN1822?

Is the finished filter scan tested, or only the media?

Is testing done one by one or by batch sampling?

What is the H13 vs H14 efficiency basis for this model?

What is the initial resistance at the rated airflow?

What is the gasket or sealing method?

Documentation questions

Can you provide a unit-level test report?

Can the report be matched to the product by serial number or batch number?

Are dimensions and airflow conditions shown on the report?

Is the scan test result clearly listed?

Project questions

Is the application a general clean area, pharmaceutical room, electronics area, or terminal supply point?

Does the system actually require H14, or is H13 sufficient?

What is the upstream filtration arrangement?

For upstream protection, many systems still compare old EN779 grades with ISO 16890 or MERV equivalents when selecting pre-filters and medium filters. Stable pre-filtration helps extend HEPA life and control pressure rise over time.

Some buyers compare quotes using only three items:

H13 or H14

Size

Price

That is not enough.

Two H13 filters may not deliver the same field performance if one has:

Weaker frame rigidity

Poor sealant control

No finished-unit scan testing

Inconsistent pleat spacing

Weak traceability

This is where factory capability matters.

ZOSLONG is a manufacturer with ISO 9001 and CE documentation, a 6000㎡ production facility, and OEM/ODM support for project-specific requirements. That means buyers can discuss not just the class, but also:

Custom dimensions

Frame options

Seal type

Application conditions

Packaging for export

Lead time control

Consistent repeat orders

That is a different conversation from buying a generic catalog item through a middle layer.

Scan-tested HEPA filters are especially important in projects such as:

Pharmaceutical cleanrooms

Semiconductor and electronics production

Hospital isolation and critical care areas

Food and beverage clean zones

Laboratory HVAC systems

Terminal HEPA boxes and FFU applications

In these environments, local leakage matters more than marketing claims.