Cleanroom HEPA Filters
The Final Barrier for Absolute Sterility
Every cleanroom is only as clean as its terminal filtration. The HEPA filter is the last line of defence — the single component where 99.97% to 99.9995% of all remaining particles are captured before the air reaches your products, patients, or processes. Metrolabs supplies factory PAO/DOP-certified H13, H14, U15, and ULPA terminal filters with purpose-designed gel-seal housings, in-situ scan test ports, and safe-change bag-in/bag-out options for every regulated cleanroom application across India.
Why the Terminal HEPA Is the Most Critical Component in the Cleanroom
Every upstream HVAC component — the AHU, the G4 and F9 pre-filters, the distribution plenum, the GI ductwork — exists to deliver clean enough air to the terminal HEPA filter. The HEPA is where ISO classification is actually achieved: without it, the cleanroom is simply a pressurised room.
Terminal Placement — Point of Entry into the Clean Zone
Metrolabs installs HEPA filters at the ceiling in purpose-designed terminal housings directly above the critical work zone. By positioning the HEPA at the point of room entry — not upstream in the AHU or ductwork — any particles introduced by the duct network downstream of the pre-filters are captured before they reach the cleanroom environment. This terminal supply approach ensures that the air reaching your product, sample, or patient is as clean as the filter’s EN 1822 efficiency specification allows.
The Seal Is as Critical as the Filter Media
A 99.995% efficient H14 filter is completely defeated if even 0.005% of air bypasses the seal between the filter and its housing. Metrolabs terminal housings use either a fluid/gel seal — medical-grade silicone gel in a perimeter channel that the filter’s knife-edge penetrates to create a continuous liquid seal — or high-compression EPDM dry gaskets for standard cleanroom grades. Both options eliminate all bypass pathways, ensuring the stated filter efficiency is the actual delivered efficiency.
In-Situ PAO Testing — Re-Validate Without Dismantling
GMP regulations require periodic HEPA integrity re-validation — typically every 6–24 months. Metrolabs terminal housings include integrated PAO/DOP aerosol challenge test ports that allow the QA team to introduce an aerosol upstream and scan the filter face and housing seal downstream without removing the filter, disturbing the ceiling panels, or exposing the cleanroom to contamination. The scan result is documented and added to the ISO 14644-2 environmental monitoring record.
Laminar Flow — Achieving the ISO Class Environment
The terminal HEPA works in combination with the fan or AHU supply to deliver filtered air at the correct velocity for the cleanroom grade — 0.36–0.54 m/s for Grade A laminar unidirectional flow. At this velocity, the filtered air creates a continuous “piston” sweeping particles from the critical work zone before they can settle. The terminal HEPA and its housing are designed so the exit velocity profile is uniform across the filter face — eliminating the dead zones and turbulence that would break laminar flow.
Four Independent Particle Capture Mechanisms
HEPA filters are not sieves — they capture particles through four distinct physical mechanisms, each dominant at a different particle size range. This is why HEPA filters are highly efficient at particle sizes both larger and smaller than their MPPS rating:
1. Sieving — Largest Particles ( > 1 μm)
The simplest mechanism: particles physically larger than the gaps between glass fibres are trapped by direct interception of the fibre matrix, just as large stones are caught in a fine mesh. Sieving captures the most abundant cleanroom contaminants — skin flakes, textile fibres, mould spores, bacterial clusters, and dust agglomerates shed by personnel and equipment. Though effective only for particles above approximately 1μm, these are precisely the particles that personnel generate in the greatest quantities, making sieving a significant first contribution to overall filter efficiency. The deep pleat structure of HEPA media dramatically increases the effective sieving surface area per unit of filter face, maximising capacity without increasing pressure drop.
Dominant: >1μm · Bacteria · Mould spores · Skin flakes2. Interception — Medium Particles (0.1–1μm)
Medium particles follow the curved airstream around fibres but cannot deviate enough to completely avoid contact when the streamline passes within one particle radius of a fibre surface — at which point the particle’s edge touches the fibre and adheres through van der Waals forces. This mechanism is the most significant for pharmaceutical contamination control: the 0.1–1μm size range includes many bacterial fragments, active pharmaceutical ingredient particles, endotoxin fragments, and fine atmospheric aerosols. Interception efficiency increases with particle size in this range and with the number of fibres per unit volume — higher-grade HEPA media uses denser fibre packing to maximise interception for pharmaceutical-grade filtration requirements.
Dominant: 0.1–1μm · API particles · Bacterial fragments3. Inertial Impaction — Heavy Particles ( > 0.5 μm)
Heavier particles carry sufficient momentum that when the airstream curves sharply around a fibre, their inertia causes them to deviate from the streamline and travel in a straighter path — colliding with the fibre surface directly. Impaction efficiency increases with both particle mass and airflow velocity, and is particularly significant for the 0.5–10μm size range. At the standard HEPA face velocity of 0.36–0.54 m/s, impaction provides meaningful capture efficiency that complements sieving and interception — the three mechanisms together providing robust multi-pathway capture across the entire supra-MPPS particle size range. Impaction is why HEPA filter efficiency actually improves significantly for particles above approximately 0.5μm.
Dominant: >0.5μm · Heavy aerosols · Droplet nuclei4. Diffusion — Smallest Particles ( < 0.1 μm)
Ultra-fine particles below approximately 0.1μm are so light that random collisions with gas molecules cause them to move erratically through Brownian motion — constantly changing direction independent of the airstream. This dramatically increases their effective path length through the filter and their probability of contacting a fibre surface. Diffusion is why HEPA filter efficiency rises sharply for the smallest particles and why the MPPS sits at approximately 0.3μm — the size where both diffusion (increasing for smaller particles) and impaction/interception (increasing for larger particles) are at their combined minimum. At 0.3μm, all four mechanisms contribute least, making it the hardest particle size to capture — which is precisely why EN 1822 specifies filter efficiency at MPPS as the worst-case acceptance criterion.
Dominant: <0.1μm · Viruses · Nanoparticles · Combustion particlesHEPA & ULPA Filter Grades — Selecting the Right Classification
EN 1822 is the definitive European standard for HEPA and ULPA filter classification. Every Metrolabs filter is individually tested, classified, and certified to this standard — with each unit’s measured efficiency printed on its factory test certificate:
| Grade | Overall Efficiency | Local Efficiency | Primary Application |
|---|---|---|---|
| H13 | 99.97% | 99.75% | Hospital OT, food cleanrooms, ISO 6–7 |
| H14✓ Pharma Std | 99.995% | 99.75% | GMP Grade A/B, ISO 4–5, aseptic filling |
| U15 | 99.9995% | 99.975% | ATMP, gene therapy, ISO 3–4 |
| U16 | 99.99995% | 99.9975% | Semiconductor, ISO 1–3 |
| ULPA | >99.9995% | — | Nanofabrication, defence research |
ⓘ All efficiency values are measured at the Most Penetrating Particle Size (MPPS ≈ 0.3μm). At all other particle sizes above and below MPPS, filtration efficiency equals or exceeds the stated values. The MPPS represents the worst-case capture condition — which is why EN 1822 specifies it as the classification criterion.
Six HEPA Housing & Configuration Options
The filter is only as effective as its housing and seal. Metrolabs supplies six terminal HEPA housing configurations matched to the cleanroom ISO class, access requirement, and biosafety level:
Standard Ceiling Terminal HEPA Housing
Recessed or surface-mounted ceiling housing integrating the HEPA filter directly into the cleanroom ceiling grid. Anodised aluminium body with flush bottom face — no particle-trapping rebate below the filter face. Gel seal or EPDM gasket options. PAO test port and downstream airflow diffusion grille included as standard. Available in 610×610mm and 610×1220mm sizes with custom dimensions for non-standard ceiling grid configurations. Standard specification for ISO Class 5–8 pharmaceutical, food, laboratory, and hospital cleanrooms.
Fan Filter Unit (FFU) with Integrated H14 HEPA
Self-contained modular ceiling unit combining a variable-speed EC fan motor and H14 HEPA filter in a single ceiling-mounted module. The FFU draws air from the ceiling plenum, filters it through the H14 HEPA, and delivers unidirectional laminar downflow directly into the clean zone below — no external AHU supply duct needed at the ceiling. Each FFU is individually speed-controlled for precise air change rate tuning. Standard for modular cleanrooms, ISO Class 3–8 applications, and retrofit projects where a ducted ceiling supply is not available or practical.
Gel (Fluid) Seal Terminal Housing — Grade A/B
The highest-integrity seal option for aseptic pharmaceutical manufacturing. A precision-machined channel around the full perimeter of the housing frame is filled with medical-grade silicone gel. The H14 HEPA filter has a matching knife-edge profile that presses into the gel on installation, displacing gel around the blade to create a continuous liquid seal with no bypass pathway — unlike compressed gaskets which can create localised low-compression bypass points. Standard WHO, US-FDA, and EU Annex 1 specification for all Grade A/B aseptic HEPA terminal installations. Mandatory where Annex 1 gel-seal documentation is required for regulatory submissions.
Safe-Change (Bag-In / Bag-Out) Housing — BSL / API
For BSL-3 and BSL-4 containment labs, high-potency pharmaceutical areas (OEL Band 5/6), and hazardous chemical processes, used HEPA filters must be removed without exposing personnel or the environment to the pathogen or compound load trapped in the media. The Bag-In / Bag-Out housing allows the contaminated filter to be enclosed in a polythene bag before it clears the housing, and the replacement filter to be introduced inside a bag that opens only within the sealed housing — maintaining containment throughout. After filter enclosure, the housing must be decontaminated (VHP or formaldehyde fumigation) before final bag removal. Mandatory biosafety requirement for BSL-3/4 exhaust HEPA.
Laminar Flow Unit — Localised Grade A Workstation
Freestanding or wall-mounted H14 HEPA unit that creates a localised Grade A / ISO Class 5 laminar flow zone over a specific workstation within an ISO Class 6–8 background cleanroom — protecting a critical weighing, sampling, or filling operation without upgrading the entire room. Telescopic height adjustment for matching workstation height. Used for high-potency API weighing, sterility testing, vial inspection, and microbiological sampling operations where Grade A protection is required at the point of use but Grade A room classification is operationally impractical. H14 gel-seal HEPA with PAO test port as standard.
BSC HEPA Replacement Module — Class II / III
Purpose-fitted replacement HEPA modules for Class II Type A2 and Class III Biological Safety Cabinets — supply HEPA and exhaust HEPA supplied as a matched, certified pair to the cabinet manufacturer’s dimensional and knife-edge specifications. PAO/DOP factory certified to EN 1822 H14 classification. Supplied with decontamination guidance and, on request, Metrolabs co-ordinates VHP cabinet decontamination before filter access as part of a single contracted replacement service. Field replacement by Metrolabs trained technicians with post-change in-cabinet PAO scan to confirm installed filter integrity before returning the BSC to service.
HEPA Filtration in Every Regulated Cleanroom Sector
Terminal HEPA filtration is the defining engineering control of the cleanroom ISO class — required by every major regulatory framework across all sectors:
Pharmaceutical GMP
H14 gel-seal terminal HEPA for Grade A laminar flow, Grade B background, and Grade C production — WHO & EU Annex 1 compliant with PAO documentation.
Aseptic & Sterile Filling
H14 / U15 terminal HEPA in Grade A filling zones — 99.995%+ filtration ensuring product sterility in injectable, biological, and ophthalmic manufacturing.
BSL-2 & BSL-3 Labs
Safe-change bag-in/bag-out exhaust HEPA for biocontainment — zero-exposure filter change protocol required for BSL-3/4. Supply HEPA H14 for negative pressure suites.
ATMP & Gene Therapy
U15 terminal HEPA for ATMP, CAR-T, mRNA, and gene therapy GMP manufacturing — ISO Class 3–4 air purity for the most sensitive biological processes.
Hospital OT & NICU
H13 / H14 laminar flow ceiling HEPA for operating theatres, NICU, and immunocompromised patient care areas — ISO Class 5–7 with positive pressure cascade.
Food & Beverage
H13 HEPA for FSSAI and HACCP high-care food production — positive pressure, no internal fibrous media, EPDM gasket seal, SMACNA-tested supply system.
Electronics & Semiconductor
H14 / U15 ceiling HEPA for ISO Class 4–7 wafer fab, precision electronics, and optical component cleanrooms — tight particle control and laminar uniformity.
NABL & Research Labs
H13 / H14 terminal HEPA for NABL-accredited testing labs — in-situ PAO test ports for documented periodic re-validation supporting ISO/IEC 17025 accreditation.
A Validated Air Quality Solution — Not Just a Filter
Metrolabs does not sell commodity HEPA filters from a catalogue. We supply a validated filtration solution — factory-certified, installed with documented seal integrity, commissioned with in-situ PAO scan, and supported with a periodic re-validation programme:
Individual PAO/DOP Factory Certificate — Every Unit
Every Metrolabs HEPA filter ships with its own individual PAO aerosol challenge test certificate showing the actual measured efficiency at MPPS — not a batch average, not a statistical sample. The certificate is your documented evidence for GMP auditors that the specific filter installed in your cleanroom was individually tested and classified to EN 1822 before it left the factory.
In-Situ Scan Port — Periodic Re-Validation on Schedule
Metrolabs terminal housings include PAO scan test ports as standard — enabling your QA team to conduct ISO 14644-3 in-situ aerosol challenge validation at whatever interval your regulatory framework demands (typically 6–24 months) without disturbing the ceiling, removing the filter, or creating a contamination risk event in the cleanroom.
Complete Safe-Change Service — BSL & High-Potency
For BSL-3 and high-potency pharmaceutical areas, Metrolabs supplies the bag-in/bag-out housing and co-ordinates the complete filter change service: VHP decontamination scheduling, trained technician PPE specification, waste classification and disposal, post-change PAO scan, and updated GMP maintenance record — all under a single contracted service.
Tiered Pre-Filtration Extends HEPA Service Life to 5–8 Years
Metrolabs always designs the complete upstream AHU filtration system — G4 coarse pre-filter protecting the cooling coil, F9 fine filter protecting the terminal HEPA — to maximise HEPA service life and minimise the frequency of disruptive and costly filter replacements in production cleanrooms. Without F9 pre-filtration, terminal HEPA service life in pharmaceutical environments is typically 12–24 months. With G4 + F9, it extends to 5–8 years.
HEPA Performance Comparison by Grade
From Filter Specification to Commissioned & PAO-Validated System
Metrolabs manages the complete HEPA filter supply chain from grade specification through in-situ commissioning scan:
Grade & Housing Specification
ISO class, GMP grade, airflow volume, operating temperature, seal type (gel/gasket), safe-change requirement, and housing frame material confirmed. Dimensions verified against cleanroom ceiling layout. Pre-filtration tiers specified in AHU for maximum HEPA service life.
Factory PAO Certification
Every filter individually PAO/DOP aerosol challenge tested at the factory. Achieved efficiency at MPPS confirmed against EN 1822 classification. Individual test certificate issued per unit — dispatched with filters for inclusion in HVAC IQ documentation.
Housing Installation & Seal
Terminal housings fitted in cleanroom ceiling grid. Gel seal channels filled or gaskets seated per manufacturer specification. Filter units seated and seal integrity confirmed visually. Protection grilles and diffusion elements fitted. Supply air velocity at filter face measured and recorded.
In-Situ PAO Scan & IQ Issue
PAO aerosol challenge introduced upstream via test port. Filter face and housing perimeter scanned with photometer. Scan confirms zero penetration and zero bypass — result documented in HVAC IQ. Periodic re-validation schedule established as part of ISO 14644-2 environmental monitoring programme.
HEPA Filtration Required by Every Major Cleanroom Regulatory Framework
WHO & EU GMP
WHO GMP and EU Annex 1 require H14 EN 1822 terminal HEPA as the minimum for Grade A and B pharmaceutical manufacturing. Both mandate documented filter integrity testing (PAO scan) at installation and at defined periodic intervals.
WHO GMP · EU Annex 1ISO 14644-3 & -2
ISO 14644-3 specifies HEPA filter testing methods and acceptance criteria for cleanroom terminal filters including in-situ aerosol challenge. ISO 14644-2 requires periodic monitoring including filter integrity verification at risk-assessed intervals.
ISO 14644-3 · -2EN 1822 & ISO 29463
EN 1822 (European) and ISO 29463 (international) govern HEPA and ULPA filter classification, testing, and marking. Every Metrolabs filter is classified and individually tested to these standards with factory certificates at handover.
EN 1822 · ISO 29463BSL & NABL
CDC/WHO BSL-3/4 containment guidelines mandate H14+ HEPA exhaust with safe-change bag-in/bag-out protocol. NABL ISO/IEC 17025 assessors require documented periodic HEPA integrity testing in controlled environment laboratories.
BSL-3/4 · NABL · GLPReady to Commission Validated HEPA Filtration for Your Cleanroom?
Contact Metrolabs for a free consultation. Our filtration specialists will assess your cleanroom ISO class, GMP grade, airflow volumes, seal requirements, and re-validation schedule — then supply and install individually PAO-certified HEPA filters with in-situ test ports and complete IQ documentation at handover.
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