AHU & HVAC Filters for Cleanrooms: Complete Guide for Pharma, Hospitals & Laboratories

Cleanrooms depend heavily on filtered air, and the real work happens inside the Air Handling Unit (AHU) and HVAC system. Whether you operate a pharmaceutical manufacturing facility, a hospital ICU, a biotech lab, or an ISO-certified cleanroom, your air quality is ultimately determined by:

• the type of filters installed
• the filtration sequence
• airflow management
• pressure control
  

In this guide, we break down everything you need to know about AHU filters and HVAC filtration stages, so you can choose the right filter combination for your cleanroom.

1. What Are AHU & HVAC Filters?

An AHU (Air Handling Unit) is the central component of any cleanroom HVAC system. It supplies clean, conditioned, and filtered air to maintain contamination control, temperature, humidity, and pressure.

Inside every AHU, there is a multi-stage filtration bank designed to remove particles at different levels.

Standard Cleanroom AHU Filtration Stages:

Stage	Filter Type	Particle Size (µm)	Purpose
1	Pre Filter	5–10 µm	Removes large dust & fibers
2	Fine Filter	1–5 µm	Removes medium particles
3	HEPA Filter	0.3 µm	Removes microbes & aerosols

This is the most widely used filtration setup in India for ISO Class 5, 6, 7, and 8 cleanrooms.

2. Why AHU Filters Are Critical in Cleanrooms

Clean rooms must maintain:

• particle count control
• microbial control
• laminar airflow
• positive pressure
• consistent temperature
• humidity balance
  

If AHU filters fail, the cleanroom fails.

Key roles of AHU filters:

• Prevent contamination
• Extend lifespan of HEPA filters
• Reduce HVAC energy consumption
• Maintain ISO/GMP/FDA compliance
• Ensure cleanroom stability
  

3. Types of AHU Filters Used in Cleanrooms

India uses several types of HVAC and AHU filters depending on industry requirements.

A. Pre Filters (G3/G4 Class)

These form the first layer of protection.

Removes:

• coarse dust
• fibers
• hair
• pollen
• general airborne impurities
  

Why Needed?

They protect downstream filters (fine + HEPA) from clogging.

Applications:

• AHU intake
• HVAC units
• ISO 7–8 corridors
• Fresh air handling units
  

B. Fine Filters (F5–F9 Class)

The second stage in the filtration bank.

Removes:

• 1–5 micron particles
• fine dust
• mold spores
• medium-sized particulates
  

Why Needed?

They protect expensive HEPA filters from premature blockage.

Applications:

• pharma manufacturing
• food processing
• hospital HVAC
• clean corridors
• labs
  

C. HEPA Filters (H13/H14 Class)

The final stage in cleanroom filtration.

Efficiency:

• H13 = 99.95%
• H14 = 99.995%
  

Removes:

• bacteria
• viruses
• aerosols
• ultrafine particles
• micro-contaminants
  

Types of HEPA used in AHUs:

• mini pleat HEPA
• deep pleat HEPA
• gel-seal HEPA (used in terminal boxes)
  

D. V-Bank Filters

A high-airflow filter used between fine and HEPA stages in large AHUs.

Benefits:

• large surface area
• low pressure drop
• high dust-holding capacity
  

Ideal for big pharma plants, FMCG units, and large R&D labs.

E. Activated Carbon Filters for VOC Removal

Used For:

• chemical fumes
• odors
• solvents
• VOCs
  

Industries like cosmetics, chemical labs, hospitals & pharma R&D frequently use carbon filters.

4. AHU Filtration Layout for Cleanrooms (Standard Setup)

Most compliant clean rooms in India (ISO 5–8) use this sequence:

S1: Pre Filter (G4)

Stops large particles, protects fine filters.

S2: Fine Filter (F7/F9)

Blocks medium particles and extends HEPA life.

S3: HEPA Filter (H13/H14)

Provides final ultra-clean supply air to the cleanroom.

5. AHU Filters for Different ISO Cleanroom Classes

ISO Class	Required Filtration
ISO 5	Pre + Fine + H14 HEPA
ISO 6	Pre + Fine + H14 HEPA
ISO 7	Pre + Fine + H13 HEPA
ISO 8	Pre + Fine + H13 HEPA

Hospitals (OTs, ICUs, NICUs) and pharma filling lines often require H14 HEPA with very low leakage (gel-seal + terminal boxes).

6. Cleanroom HVAC: Airflow Patterns

Cleanroom HVAC must maintain:

Laminar Flow

• uniform air distribution
• minimal turbulence
• high-volume HEPA filtered air
  

Recirculation Airflow

• Air returns to AHU after filtration.

Positive Pressure

• Prevents outside contamination.
• Critical for pharma & hospital sterile areas.

7. How to Choose the Right AHU Filters

Choosing the correct filters depends on:

A. Cleanroom Class & Industry

Pharma sterile rooms – H14 HEPA
API rooms – H13 HEPA
Hospital OT – H14 + laminar flow
R&D labs – H13

B. Airflow & Pressure Drop

Filters with low resistance improve:

• AHU efficiency
• energy consumption
• airflow stability
  

C. Filter Media & Build Quality

Choose filters with:

• microglass fiber media
• strong aluminum or GI frame
• polyurethane or epoxy sealing
• DOP/PAO testing
  

D. Temperature & Humidity Conditions

High-temperature HEPA filters are required for certain applications.

E. Sterile Zone Requirements

Gel-seal HEPA filters are mandatory for:

• sterile manufacturing
• oncology
• BSL2/BSL3 labs

8. When to Replace AHU Filters

Replacement depends on:

• pressure drop reading
• AHU strain
• contamination level
• cleanroom stability
  

Typical Replacement Timeline:

• Pre Filter – every 1–3 months
• Fine Filter – every 3–6 months
• HEPA Filter – every 12–24 months
  

(Actual lifespan varies based on environment and air volume.)

9. Common Problems Caused by Poor AHU Filtration

• contamination build-up
• frequent HEPA blockages
• HVAC overload
• high energy bills
• increased microbial presence
• ISO class failure
• batch rejection in pharma

A proper filtration system eliminates these risks.

10. Industries Using AHU & HVAC Cleanroom Filters

• Pharmaceuticals
• Biotechnology
• Hospitals
• Electronics & Semiconductor
• IVF Centres
• Food & Beverage
• Cosmetic Manufacturing
• Medical Device Factories
• R&D Laboratories
  

Each industry has unique airflow and contamination control requirements.

Conclusion

AHU and HVAC filters are essential for cleanroom air quality. Whether it’s pre filters, fine filters, HEPA filters, V-bank filters, or activated carbon filters each plays a crucial role in protecting your manufacturing environment.

Choosing the right AHU filters ensures:

• long-term cleanroom stability
• controlled contamination
• compliance with ISO 14644 & GMP
• improved product quality
• lower energy costs
• increased equipment longevity

If you’re setting up a clean room or want to upgrade your existing filtration system, always work with filters that meet global standards, have efficient airflow characteristics, and come from trusted manufacturers in India.