Technical standards of HEPA H14 filter in operating room

In the cleanroom and medical industry, the technical standards of HEPA H14 filters play a crucial role in ensuring air quality and microbiological safety in strict environments such as operating rooms, pharmaceutical production areas or sterile operating cabinets. HEPA H14 filters, according to EN 1822 standards, have a filtration efficiency of up to ≥ 99.995% for particles of MPPS size. When designing air systems for areas requiring high cleanliness, choosing H14 standard filters and individual leak testing is indispensable to comply with ISO/GMP standards. In this article, we will analyze in detail the technical parameters you need to know - from efficiency, leak testing to size, differential pressure - to help you understand and apply HEPA H14 filters properly in medical and cleanroom environments.

1. What is HEPA H14 and Its Role in Operating Rooms

In cleanroom air filtration systems, HEPA (High Efficiency Particulate Air Filter) plays the most critical role - responsible for removing ultrafine dust particles and microorganisms from the air. It is the final filtration stage in the multi-layer air purification chain (G4 - F7 - H14), directly determining the cleanliness level of the operating room.

Definition and Standard of HEPA H14

According to the European EN 1822 standard, HEPA filters are classified from H10 to H14 based on their ability to capture the smallest particle size - called MPPS (Most Penetrating Particle Size). Among these, H14 represents the highest grade, with a filtration efficiency of ≥ 99.995% at 0.3µm - meaning that out of 100,000 particles passing through, no more than 5 can escape.

This extremely high efficiency is sufficient to remove almost all bacteria, fungal spores, cell fragments, PM2.5 fine dust, and airborne contaminants. Therefore, H14 is regarded as the “final lung” protecting sterile environments in hospitals and surgical areas.

The Role of HEPA H14 in Operating Rooms

In an operating room, the air must reach ISO Class 5 (ISO 14644-1) or the equivalent Class 100 (FS 209E). At this level, the concentration of particles ≥0.5µm must not exceed 3,520 particles/m³ - an extremely strict requirement.

To achieve this, air supplied into the operating room must pass through HEPA H14 filters, typically installed in the ceiling as HEPA Boxes or FFUs (Fan Filter Units), creating a laminar airflow that continuously flows downward over the surgical field. This design ensures that bacteria and airborne particles cannot recirculate or accumulate around the operating table, helping to:

• Reduce the risk of Surgical Site Infections (SSI).
• Protect the sterile surgical field.
• Maintain positive pressure in the operating room relative to corridors, preventing contaminated air from entering.

Comparison Between H13, H14, and ULPA (U15-U17)

As shown above, H14 provides the optimal balance between filtration efficiency, airflow, and operational cost. While ULPA filters offer higher efficiency, they cause higher pressure drops and reduced airflow, making them impractical for operating rooms that require stable, gentle air circulation.

Therefore, HEPA H14 is the ideal technical standard for modern operating rooms - where air purity must be nearly absolute yet airflow, temperature, and humidity must remain stable to support both patients and medical staff.

2. Technical Standards Required for HEPA H14 Filters in Healthcare Environments

In hospital clean air systems, HEPA H14 is not merely an “air filter” but a medical-grade component regulated under international standards such as EN 1822, ISO 29463, TCVN 9381, and guidelines from WHO, EU GMP, and ISO 14644-1.
Below are the key technical requirements that must be followed when selecting and installing HEPA H14 filters in operating rooms.

Filtration Efficiency - ≥ 99.995% @ MPPS

The filtration efficiency of H14 is measured at the Most Penetrating Particle Size (MPPS), typically between 0.1-0.3µm.
According to EN 1822-1:2019, a filter must achieve overall efficiency ≥ 99.995% to be classified as H14.
This ensures that almost all dust, bacteria, and microorganisms in the air are eliminated - a critical factor in maintaining a sterile surgical environment.

Filter Media - Ultrafine Glass Fiber / PTFE / ePTFE

The filter media directly affect both performance and lifespan:

• Glass fiber: the most common choice, resistant up to 250°C and stable over time.
• PTFE or ePTFE: ideal for environments with high humidity, chemical exposure, or steam sterilization.
• Pleated paper structure: increases surface area, reduces pressure drop, and optimizes airflow.

All materials are produced under static-controlled conditions and free from formaldehyde - ensuring biosafety compliance for medical applications.

Frame - Aluminum / Coated Steel / Stainless Steel 304

The frame secures the filter media and prevents leakage:

• Aluminum: lightweight, durable, and easy to install.
• Coated steel: cost-effective but not recommended for operating rooms.
• Stainless steel 304: the preferred choice for hospitals due to corrosion resistance and cleanability.

All frames must be airtight, with no gaps greater than 0.5mm, as per GMP recommendations.

Sealant and Gasket - Ensuring Airtight Integrity

Sealant and gasket quality determine the system’s leakage resistance:

• Polyurethane or silicone sealant: flexible, heat-resistant, non-toxic.
• Inorganic high-temperature sealant: for high-heat applications up to 350°C.
• EPDM or Neoprene gaskets: maintain a tight seal and stable positive pressure.

During installation, the gasket must be fully compressed to eliminate bypass leakage - one of the most common causes of DOP test failure.

Nominal Air Velocity - 0.45 m/s ±20%

The nominal airflow velocity is designed at 0.45 m/s (±20%), equivalent to 0.36-0.54 m/s. This ensures:

• Stable laminar airflow in the operating field.
• Prevention of turbulence that can spread contaminants.
• Uniform clean air coverage across the surgical zone.

Measurements taken onsite must remain within this tolerance - below 0.36 m/s reduces air exchange efficiency, while above 0.54 m/s causes turbulence around the operating table.

Initial Pressure Drop - 220-250 Pa

Pressure drop (ΔP) represents airflow resistance through the filter:

• Initial value: 220-250 Pa at nominal velocity.
• Replacement limit: 400-450 Pa.

Once ΔP exceeds the threshold, the filter must be replaced to maintain proper airflow and avoid excessive fan load.
Modern operating rooms are equipped with differential pressure gauges to monitor this parameter continuously.

Certification Standards - EN 1822 / ISO 29463 / TCVN 9381

These international standards define testing and classification methods for HEPA filters:

• EN 1822-1:2019: European classification system (E10-U17).
• ISO 29463: global equivalent to EN 1822.
• TCVN 9381:2012: Vietnamese adaptation of EN 1822.

Each certified filter must include a test certificate with serial number, test date, MPPS results, efficiency, and leakage rate, issued by an independent testing laboratory.

Leak Testing - DOP / PAO Test

After installation, each HEPA H14 filter must undergo onsite leak testing (in-situ test):

• Method: DOP or PAO aerosol test.
• Principle: aerosolized oil particles are introduced upstream; a particle counter scans the downstream surface to detect leaks.
• Acceptance criterion: leakage ≤ 0.01%.

To conduct this test, the HEPA Box must include a DOP port, which is mandatory for all GMP- and ISO 14644-compliant operating room designs.

See more: Important differences in the production of HEPA Filters H13 and H14

3. Configuration of HEPA H14 Installation in Operating Rooms

Selecting and correctly arranging the HEPA H14 filter configuration is a key factor determining the air quality in an operating room. Even if the filter meets EN 1822 or ISO 29463 standards, if the airflow is not distributed according to the laminar principle or if the room pressure is not properly balanced, the sterile performance will be significantly compromised.

Below are the standard technical configurations applied in the design and construction of GMP- and ISO 14644-compliant operating rooms.

3.1 HEPA Box Terminal - Ceiling Mounted with DOP Port and Damper

In most operating rooms, HEPA H14 filters are installed at the final point of the air supply path, directly at the ceiling, in the form of HEPA Box terminals.

The HEPA Box typically includes:

• Airtight housing made of stainless steel 304 or electrostatic powder-coated steel.
• Air inlet connection for soft or rigid ducts connected to the AHU system.
• Airflow damper to balance the air volume at each filter location.
• DOP port for leak testing (PAO/DOP test) without removing the filter.
• Filter slot matching the standard size (usually 610×610×150 mm).

Installing HEPA Boxes in the ceiling saves space, ensures aesthetics, and allows for easy removal and maintenance. Each operating room generally contains 4-12 HEPA Boxes, evenly distributed above the surgical table depending on the room’s area.

3.2 Integration of FFU (Fan Filter Unit) for High Airflow Zones

In large operating rooms, transplant rooms, or those with multiple heat-generating devices (surgical lamps, anesthesia machines, monitors, etc.), the central AHU system may not provide sufficient or adjustable airflow.

The solution is to use FFUs (Fan Filter Units):

• Each FFU integrates a fan motor and HEPA H14 filter, operating independently.
• Increases localized clean air volume directly above critical surgical zones.
• Allows individual airflow control for specific zones (surgical table, staff area, instrument sterilization area).
• Reduces pressure loss in long duct runs and improves energy efficiency.

Combining HEPA Boxes and FFUs creates a flexible configuration suitable for laminar flow in the central area and turbulent flow in surrounding areas, maintaining aerodynamic balance within the operating room.

3.3 Use of Plenum Box for Even Air Distribution

The Plenum Box (intermediate air distribution chamber) is a technical solution designed to evenly distribute airflow from the AHU before it reaches each HEPA Box. It helps to:

• Minimize uneven airflow velocity between supply points.
• Reduce vibration and noise.
• Facilitate integration of pressure and flow sensors for monitoring.

Plenum boxes are usually installed above the technical ceiling, insulated to prevent condensation, and equipped with an access panel for maintenance.

3.4 Arrangement Based on the Laminar Airflow Principle

Modern operating rooms follow the “clean-to-dirty” concept - clean air flows from the most sterile area to less critical areas. To achieve this, HEPA H14 filters must be positioned so that the air is supplied vertically and unidirectionally from the ceiling downward - a setup known as laminar airflow.

Arrangement principles:

• The area directly above the operating table uses HEPA H14 filters with the highest airflow rate, creating a central clean air zone.
• Surrounding areas use HEPA Boxes or FFUs with lower airflow.
• Return air grilles are installed low near the floor to remove contaminated air.

This airflow pattern pushes bacteria and particles downward and out of the surgical area, preventing turbulence and recirculation within the operating space.

3.5 Maintaining Positive Pressure Between the Operating Room and Corridor (≥10 Pa)

Another critical design factor is pressure balance.

• The air pressure in the operating room must be at least 10 Pascals higher than in adjacent corridors.
• This ensures that when doors open, air flows from the operating room outward, preventing contaminated air from entering.

Positive pressure is maintained by adjusting the supply airflow to be greater than the exhaust airflow, typically maintaining a 10-15 Pa differential.
A centralized control system (BMS or DDC) continuously monitors the pressure through differential pressure sensors mounted on the wall or ceiling of the operating room.

4. Inspection and Maintenance Procedures

HEPA H14 filters in operating rooms must not only meet standards upon installation but also be regularly inspected, monitored, and maintained to ensure sustained performance. A system that is not properly maintained may lose its cleanliness level, increase the risk of infection, and fail to comply with GMP or ISO 14644 standards.

The following outlines the standard inspection and maintenance procedures for HEPA H14 filtration systems in healthcare environments.

4.1 Periodic Efficiency Testing - Every 6 to 12 Months

According to ISO 14644-3 and GMP Annex 1, the filtration efficiency of HEPA H14 must be verified at least once per year, or every six months for high-usage operating rooms.

The inspection includes:

• Actual efficiency compared with the original EN 1822 test report.
• Detection of leakage at the frame, gasket, or HEPA Box joints.
• Airflow uniformity across the entire filter surface.

All test results must be recorded in an in-situ test report and kept as part of the operating room’s maintenance documentation.

4.2 Measuring Differential Pressure and Air Velocity

Two critical parameters must be continuously monitored:

• Differential pressure (ΔP): indicates filter clogging.
• Air velocity: ensures adequate air supply to maintain the cleanliness class and positive pressure.

Procedure:

1. Measure ΔP using the fixed differential pressure gauge on the HEPA Box or control panel.
2. Measure air velocity at multiple grid points (6×6 or 9×9) using an anemometer.
3. Compare results with design values (0.45 m/s ±20%, ΔP 220-250 Pa).

If ΔP increases abnormally or velocity decreases, inspect for possible clogging, dust accumulation, or gasket damage.

4.3 Filter Replacement - When ΔP Exceeds 400-450 Pa or After 12 Months

The average service life of a HEPA H14 filter in operating rooms ranges from 6-12 months, depending on environmental conditions and pre-filter (G4/F7) quality.

Filters must be replaced immediately in cases of:

• ΔP exceeding 400-450 Pa, even after cleaning ducts and pre-filters.
• Failing the DOP/PAO leak test.
• Moisture, mold, or frame deformation.
• Reaching 12 months of service, per GMP maintenance policy.

Replacement filters must match the same model, efficiency grade, and valid EN 1822/ISO 29463 certification.

4.4 Leak Testing - Using PAO Test Onsite

The PAO test (Poly Alpha Olefin) or DOP test is the most important quality verification step for HEPA filters.
Procedure:

1. Introduce aerosolized PAO particles upstream through the DOP port.
2. Use a particle counter to scan the downstream surface and identify leaks.
3. Acceptable leak rate: ≤ 0.01%.

If leaks are detected, engineers must determine the cause - gasket failure, warped frame, or sealant gaps. Minor defects can be repaired with medical-grade silicone, but major leaks require complete filter replacement.

4.5 Documentation and Record Keeping per GMP - ISO 14644

All inspection, replacement, and measurement activities must be fully documented and archived, including:

• Original manufacturer test certificates.
• Periodic DOP/PAO test reports.
• Differential pressure and velocity measurement records.
• Filter replacement logs (date, serial number, personnel).

These records serve as GMP compliance evidence and are critical for traceability in the event of contamination or quality control failures.

See more:Latest price list of HEPA filters used in medical clean rooms

5. Notes When Selecting HEPA H14 Filters for Operating Rooms

In the design and operation of operating rooms, choosing the correct HEPA H14 filter is not just a technical matter but is directly related to patient safety and regulatory compliance. A substandard or uncertified filter can compromise the entire HVAC system, increase the risk of infection, and fail GMP inspections.
Below are four key factors to consider when selecting HEPA H14 filters for hospitals or surgical centers.

5.1 Choose Suppliers with EN1822 / ISO29463 Certification

This is a mandatory requirement. Every HEPA H14 filter installed in an operating room must include:

• A Test Report from an independent laboratory according to EN 1822-1:2019 or ISO 29463.
• Clear documentation of efficiency at MPPS, classification (e.g., H14 - 99.995%), and maximum allowable leakage ≤0.01%.
• A Batch Number for full traceability.

Selecting a reputable supplier ensures reliability and consistency between production batches, reducing the risk of DOP test failure during on-site validation. Leading international brands often hold ISO 9001 and ISO 14001 certifications for production processes and test each filter individually before shipment.

5.2 Prioritize Filters with DOP Port and Airflow Damper

When installed in medical HVAC systems, H14 filters should come with technical accessories that facilitate operation and validation:

• DOP port: allows quick PAO/DOP leak testing without removing the filter. This is mandatory in all GMP-compliant HEPA Box designs for operating rooms.
• Airflow damper: balances air volume in each zone, preventing “dead spots” or excessive pressure differences.
• Stainless steel 304 or anodized aluminum frame: ensures airtight sealing and long-term durability in frequently sterilized environments.

These design features not only simplify validation but also enhance airflow precision and stability of the laminar air distribution in the operating room.

5.3 Check Traceability Documentation

A medical-grade HEPA H14 filter must include a traceability file consisting of:

• Lot/Batch number.
• Test date and testing facility (including the laboratory name and test engineer’s signature).
• EN1822 / ISO29463 test results.
• Matching serial label affixed to the filter body corresponding with the test report.

This documentation enables hospitals to easily track usage cycles, replacements, and periodic inspections. It also serves as a mandatory record during GMP or ISO 14644 audits.

5.4 Coordinate with the HVAC Team to Ensure System Compatibility

Equally critical is close coordination between the HVAC engineering team and the filter supplier.

• Air volume, velocity (0.45 m/s ±20%), and positive pressure (≥10 Pa) must be calculated consistently from AHU → ducts → HEPA Box.
• Selecting filters with incorrect specifications (too thick or high pressure drop) can overload the fan system and disrupt the pressure balance.
• Conversely, filters with lower-than-specified pressure drop may cause excessive airflow velocity, leading to turbulence in the laminar airflow zone around the surgical table.

A proper commissioning process always involves both parties - HVAC engineers and filter suppliers - performing joint tests of airflow velocity, differential pressure, and DOP leak testing to confirm full system compatibility.

6. Frequently Asked Questions

Can H13 filters replace H14 in operating rooms?

No. H13 filters have an efficiency of 99.95%@MPPS, suitable only for ISO 7-8 cleanrooms (such as compounding or packaging areas). Operating rooms require ISO Class 5 (Class 100) conditions with extremely low particle concentrations - achievable only with H14 (99.995%@0.3µm) filters.
Furthermore, international standards such as EU GMP Annex 1 and WHO TRS 961 specify that surgical rooms, transplant areas, and sterile zones must use H14 or higher filters.

What is the lifespan of a HEPA H14 filter?

On average, between 6-12 months, depending on system operation and prefilter quality.

• Systems with properly maintained coarse (G4) and fine (F7) filters can extend H14 lifespan to 12 months.
• In dusty, humid, or high-duty environments (≥12 hours/day), inspections should be done every six months.
• Replace immediately when ΔP exceeds 400-450 Pa to maintain airflow and room pressure.

Tip: Install differential pressure gauges on each HEPA Box to monitor filter condition accurately instead of relying solely on usage time.

How to verify if an H14 filter is compliant?

A compliant medical-grade filter must include:

• EN1822 or ISO 29463 test certificate indicating MPPS efficiency, serial number, and test date.
• DOP port for on-site leak testing (PAO/DOP test).
• Efficiency ≥99.995%@0.3µm meeting H14 classification criteria.
• Traceable label with batch number, inspection code, and testing laboratory.

Missing any of the above means the product is not a certified medical-grade H14 filter.

Should the entire filter be replaced when pressure drop is high?

Yes. When ΔP exceeds 400 Pa, the filter is clogged and no longer delivers the designed airflow (0.45 m/s ±20%).
If not replaced in time, this can result in:

• Reduced cleanliness level and higher infection risk.
• Increased AHU load and energy consumption.
• Turbulence and instability in the sterile airflow zone.

Therefore, filters must be replaced with the same H14 grade and specifications, followed by recalibration of airflow velocity and positive pressure to restore balance.

7. Contact VCR for Consultation and Support

VCR is a leading supplier and installer of HEPA H14 filters for operating rooms.
With over 10 years of experience in medical cleanroom solutions, VCR provides complete services - consulting, design, installation, testing, and maintenance - ensuring your operating rooms always meet ISO 5 / Class 100 standards and comply fully with GMP, WHO, and ISO 14644 regulations.

Featured Products

• HEPA H14 Filters certified under EN 1822 / ISO 29463, efficiency ≥99.995%@0.3µm.
• HEPA Box H14 with integrated DOP port and airflow damper, validated by DOP/PAO testing at factory or on-site.
• FFU (Fan Filter Unit) for high airflow zones, designed for compatibility with surgical room ceilings.
• Supporting accessories: differential pressure gauges, F7 fine filters, pressure and airflow sensors.

VCR provides not just equipment, but a long-term commitment to clean air quality and biosafety assurance for every healthcare environment.

Hotline: 090.123.9008
Email: [email protected]
Website: https://airfilter.vn/

Diep VCR