How Do Cleanrooms Work in the Medical Industry?

Introduction

Cleanrooms in the medical sector function by consistent air filtration, pressure regulation, and contamination prevention to ensure the safety and health of patients and sterilized products.

These controlled areas ensure the maintenance of specific ISO standards in air cleanliness with a combination of HEPA filtration, guided airflow, and operational requirements.

This article describes how cleanrooms work in the medical industry by discussing the core principles of operation of pharmaceutical cleanrooms, air filtration, contaminants control measures, and other key aspects.

Cleanroom operation involves a distinct process that is regulated at every step. The first stage entails air intake via vents where air goes through several layers of filters before being fed into the clean space through controlled airflow.

Positive pressure is employed to prevent contamination from outside. After leaving the cleanroom, a percentage of air is recirculated while some is expelled. Barriers prevent personnel and materials from contaminating the cleanroom.

Medical cleanrooms are not merely clean environments. They are predetermined environments that ensure cleanliness of one cubic meter of air, control over each differential pressure, and particle counting against specifications.

Core Operating Principles of Medical Cleanrooms

Medical cleanroom operating principles begin with a filtration cascade, and the subsequent movement of air is done in a controlled manner to prevent contamination from re-entering critical areas. The room is recognized as being a system rather than just a spatial area.

The underlying principle is simple. Contaminations inside the medical cleanroom get either diluted or washed away by air that enters after going through filtration.

Contaminations from outside the cleanroom are kept away through suitable pressurization of the cleanroom.

The air that leaves the cleanroom can be through either the low return grilles or exhaust systems. Some of the air recirculates back through filtration and a little is released outside. This closed loop control maintains a constant level of pressurization.

The medical cleanroom pressure differential acts like an impenetrable barrier between clean and unclean air. The cleanroom is always under positive pressure, hence it forces clean air through every crack and prevents unclean air from entering.

Unidirectional vs Turbulent Airflow Mechanisms

Unidirectional airflow, sometimes called laminar flow, moves air in parallel lines at a uniform velocity. In medical cleanrooms it is used over critical zones such as aseptic filling stations and operating tables.

The velocity usually runs from 0.3 to 0.5 meters per second, fast enough to sweep particles away without disturbing the sterile field.

Turbulent airflow utilizes dilution. Air enters through the ceiling diffusers and gets mixed with the room air, thereby reducing the concentration of particles. This process is used in clean zones where the contamination risks are low and the required ISO classes are less stringent.

Clean areas are located according to this organizing principle. The most critical operations are performed directly under unidirectional supply, and the support areas around them have turbulent dilution. Therefore, one cleanroom suite can have a variety of ISO classes corresponding to various contamination risks.

Medical Cleanroom Pressure Differential Control

One of the important contamination control principles in medical cleanrooms is pressure differential. Pressure differential is the pressure hierarchy between adjacent areas.

• Moving air prevents external contamination from entering the cleanroom through gaps, door frames, and service penetrations.
• A differential of 10–15 Pa is standard between adjacent cleanliness grades.
• Zones with higher cleanliness grades hold higher pressure than zones with lower cleanliness grades.
• Continuous monitoring is necessary to detect any loss of differential that could compromise sterility.

The Deiiang catalogue shows that tongue-and-groove panel joints and coved aluminum profiles are built with airtight seals, which contributes to maintaining stable pressure differentials.

Installation details specify fasteners at 300 mm intervals and attachment points at 1,200 mm spacing to avoid deflection and opened gaps.

According to advice from Deiiang designer Jason Peng, door gasket aging and loose wall seals are the two main reasons for pressure differential failure. Quarterly inspection of full-length gaskets is recommended, with modular cable seals used instead of field caulk.

Pharmaceutical Cleanroom Air Filtration Systems

Pharmaceutical cleanroom air filtration systems consist not of one stage, but of cascading stages through which the air passes successively, with a progressively smaller number of particles trapped in each stage.

The purpose of multiple filters is to ensure adequate service life of filters and to keep operating costs as low as possible. Each filter takes on responsibility for trapping a particular size of particle.

Large particles are first filtered by a G4 pre-filter, which prepares the air for smaller particles before reaching the HEPA or ULPA filter. That final stage can efficiently trap submicron particles with over 99.95% filtration efficiency.

The Deiiang catalogue provides the necessary data. A 592 mm × 592 mm × 292 mm H13 filter is rated to deliver 1,900 m³/h, with a filter surface area of 15.03 m² and an initial resistance of 200 Pa or less.

The same frame size produces 2,500 m³/h in the 4-pleat configuration, with a starting resistance not exceeding 220 Pa. Replacement is then due when the overall resistance reaches between 400 and 600 Pa.

Multi-Stage Filtration Stage Architecture

Each filtration stage has a specific purpose, and omitting one requires the remainder of the filter system to take on the responsibility.

• G4 pre-filter: collects larger particles such as dust or lint so downstream filters are not overloaded.
• F8 medium efficiency filter: claims 90% efficiency at 0.5 µm, extending HEPA lifespan.
• H13/H14 HEPA final stage: 99.97–99.99% for H13, or 99.995–99.999% for H14, at 0.3 µm.
• U15–U17 ULPA: used in highly critical areas, filtering particles of 0.12 µm and above.

According to a note from Jason Peng, removing the F8 medium efficiency filter reduces the purchase cost but can cut HEPA service life by more than 60%.

Regarding general ventilation filters, the old EN 779 standard was officially withdrawn in 2016 and replaced by ISO 16890, which classifies them by ePM1, ePM2.5, and ePM10 ratings [10]. HEPA and ULPA classification still follows EN 1822 and ISO 29463 [9].

Deiiang HEPA & ULPA Filter Performance

Deiiang supplies combined high-efficiency filters, DOP integrated filters, and super high-efficiency baffle-free filters. The DOP integrated design suits medical cleanrooms with limited plenum height, since the box structure includes a built-in air inlet pipe of 250–350 mm diameter and a DOP test port.

Filter performance is summarized in Table 1.

Table 1: Performance data of HEPA and ULPA filters manufactured by Deiiang

Hospital Cleanroom HVAC Systems Design & Operation

Hospital cleanroom HVAC systems perform the important function of providing filtered air and controlling temperatures, humidity levels, air change rates, and pressure differentials. These HVAC systems establish how hospitals use their medical cleanrooms to attain optimal patient health.

An improperly designed system will create pressure differentials that can draw contaminated air into an operating theater or compounding pharmacy.

A hospital cleanroom HVAC system needs to operate efficiently despite variable load conditions. An operating room occupied by surgical staff generates a lot of heat and moisture, unlike an unoccupied room. The system must adjust supply airflow and temperature so these variables remain unchanged.

The design consideration for hospital cleanrooms is infection control. The system is designed to accommodate the infection risk in each section, including operating rooms, isolation rooms, and sterile compounding rooms.

Air Change Rates & Ventilation Ratios

Air change rate (ACH) refers to the frequency of air replacement of the complete volume of air in a room with filtered air. Greater ACH yields a greater dilution of contaminants in the air.

The usual ACH benchmarks for medical cleanrooms are presented in Table 2.

Table 2: Common ACH benchmarks for medical cleanroom spaces

Deiiang AHU design data for pharmaceutical applications uses modular cleanroom panel systems with MGO or rockwool cores, sized from 2 m × 3 m × 3 m to 10 m × 8 m × 3 m. Panel thickness varies between 50 mm and 100 mm.

Clinical Environmental Control Parameters

The temperature in medical cleanrooms is usually held between 20–24°C. Relative humidity aims for 45% to 60%. This balance is necessary for patient and staff comfort.

The following environmental parameters are used:

• Temperature: 20–24°C, balancing patient and staff comfort.
• Relative humidity: 45–60%, controlling static charge and microbial growth.
• Pressure cascade: the surgical room holds the highest pressure, the scrub corridor a lower level, and the outer corridor the lowest.
• Backup power: mandatory for any crucial HVAC element.

The pressure cascade allows clean air to flow through a door into a less clean area and prevents contamination from moving back into the sterile zone.

If the rate of air handling within the operating room drops during surgery, it becomes a safety issue for the patient and not simply a comfort matter.

Cleanroom Contamination Control in the Medical Industry

To ensure cleanroom contamination control medical industry practice holds up, it is first important to determine what type of contaminants are present. The primary source of contaminant particles in the medical cleanroom is the human factor.

A walking person sheds 5–10 million particles per minute according to cleanroom research. At rest, that number falls by roughly an order of magnitude, which is why movement is limited.

Microbial control is preferred over inert particulate control in medical cleanrooms, as it involves risk to patients and products.

The material transfer process provides an additional pathway. Each box, tray, or instrument brought into a cleanroom contributes contaminant particles carried on its surface.

If the transfer method does not involve an airlock or controlled entry mechanism, then contamination occurs. A third source is equipment-generated particles from motors, bearings, and friction surfaces, controlled through maintenance procedures and localized exhaust.

These procedures are implemented to ensure two major objectives: patient safety and sterility of the product. An infection in the operating room or a contaminated injectable is the result of a contamination control failure. Auditing readiness relies on documented proof of compliance.

Particle & Microbiological Contamination Sources

With knowledge of the sources of contamination, one can easily see the control strategy.

• Human skin shedding: squames and skin flakes are the main carriers of microorganisms; one person can shed millions of particles in an hour.
• Equipment-generated particles: motors, conveyors, and robotic arms create wear particles during operation.
• Bioburden of raw material: incoming materials carry microbial contamination that requires reduction.
• Air ingress: leaks can occur through door seals, cable penetrations, and panel joints.

Medical cleanrooms control viable particles such as bacteria and fungi, and endotoxins, apart from just inert particles. This matters because sterility and patient safety impose a microbiological requirement absent in general industrial cleanrooms.

The control of particle count is the first line of microbial control. The majority of microbes are carried by skin squames or dust particles. Once the carrier particles are eliminated, the microorganisms are removed with them.

Mitigation Protocols & Barrier Design

The barrier strategy has four levels, and each level is directed towards a specific pathway for contamination.

• Personnel: standardized gowning using gowns, hoods, boots, and gloves in a particular sequence.
• Material: airlocks, pass boxes, or transfer hatches designed to stop direct air exchange between rooms.
• Air: Deiiang airlocks using interlocked doors in Grade A/B cleanrooms.
• Surface: scheduled disinfection of floors, walls, and surfaces that equipment contacts.

Deiiang cleanroom panel installation data requires coved aluminum corners in gmp clean areas to eliminate dust-collecting dead corners. L-angle corners are allowed for unclassified partitions only.

iso 14644 Medical Cleanrooms: Classification & Compliance

ISO 14644 medical cleanrooms are classified according to the maximum allowable concentration of airborne particles of specified dimensions. iso 14644-1:2015 [1] defines ISO 1 (cleanest) to ISO 9, along with maximum allowable particle concentrations per cubic meter of air. Medical applications generally use ISO 5 to ISO 8.

The classification system offers a common language for facility managers. An iso 5 cleanroom at a pharmaceutical facility and an ISO 5 cleanroom in a hospital pharmacy meet the same particle concentration limits, in spite of different operational protocols. This also makes supplier qualification and audit preparation easier.

Compliance includes classification but goes further than it. A cleanroom classified as ISO 7 in the at-rest condition can fail to maintain that classification under operating conditions.

Regulations including EU GMP Annex 1 [4], FDA 21 CFR Part 211 [5], and USP <797> [6] provide operational specifications that a classification certificate does not cover.

ISO 14644-1 Classification for Medical Applications

ISO 14644-1 limits of particle count for cleanroom classes in medical applications are given in Table 3.

Table 3: ISO 14644-1 particle count limits for medical cleanrooms

ISO 5 is the essential aseptic area. ISO 7 allows general sterile work. ISO 8 handles packaging and other less strict operations.

Global Regulatory Compliance Framework

EU GMP Annex 1 [4] aligns Grade A with ISO 5 in both resting and operational conditions, Grade B with ISO 5 or ISO 6, grade c with ISO 7, and Grade D with ISO 8. Grade A and B areas undergo requalification at least twice a year; Grade C and D areas at least once a year.

FDA 21 CFR Part 211 [5] sets standards for pharmaceutical manufacturing facilities, including procedure manuals for cleaning, maintenance, and environmental monitoring.

USP <797> [6] regulates sterile compounding in the hospital pharmacy, requiring ISO 5 in critical compounding and ISO 7 in the buffer area.

PIC/S GMP [7] alignment means inspection findings in one jurisdiction carry weight in others. Medical cleanroom compliance requires ongoing, documented control rather than one-time certification, with emphasis on data integrity, audit trails, and batch traceability.

This differs from compliance for industrial cleanrooms, which focuses more on initial certification than on continuous documentation.

Medical Sector Cleanroom Application Use Cases

There are a number of ways of applying cleanrooms in the medical field, including pharmaceutical manufacturing, medical device manufacture, and hospitals.

Each of these applications has its own unique cleanroom use, where the risk profile dictates the design of the cleanroom.

Pharmaceutical manufacturing prioritizes preventing cross contamination and microbiological control. Medical device manufacturers emphasize control of particulates and, sometimes, ESD. For hospitals, the cleanroom is applied in infection control.

The case study below illustrates how this works in practice in one specific installation.

Pharmaceutical Manufacturing Cleanrooms

In one packaging cleanroom in eastern China, the aim was to create a cleanroom with an ISO class of 6 (class 1000). Three challenges had to be overcome: very high levels of ambient contamination, pressure drop limits needed to maintain laminar flow, and limited ceiling plenum height.

Deiiang supplied low-profile H14 filters (592 mm × 592 mm × 292 mm, 2,500 m³/h, ≤220 Pa initial resistance, 20.04 m² of filter media), together with silicone-free sealing gaskets and F7 pre-filters.

Jason Peng's team carefully considered pressure drop limits when selecting the low-profile H14 filters, and each unit underwent DOP scanning before delivery.

As reported by the project, this selection reduced particle counts from ISO 7 levels to a stable ISO 6, and also achieved energy savings due to the low initial pressure drop.

Aseptic filling lines represent the most critical aspect of cleanroom operations in the pharmaceutical industry. The filling area operates within ISO 5, with surrounding areas usually at ISO 7 or ISO 8. Contamination between product lines is prevented through pressure cascades and separate HVAC systems.

Medical Device Manufacturing Cleanrooms

In most instances, medical device manufacturing cleanrooms are classified under ISO 7 or ISO 8. The exact specification depends on the classification of the medical device. Here are some basic specifications.

• Implantable device assembly generally falls under ISO 7, requiring particulate and microbiological monitoring.
• Sterile packaging runs at ISO 8 for the packaging area, while the product exposure area is ISO 7.
• ESD control is achieved through conductive floors and grounded workstations.
• Dedicated storage cabinets hold cleanroom garments until they are used.

These specifications ensure that medical device manufacturing cleanrooms can operate under conditions of cleanliness and without ESD issues.

Hospital & Clinical cleanroom environments

The clean air suites used for operating rooms apply unidirectional flow over the surgical field at air speeds of 0.3–0.5 m/s, with a required air change rate of 60 ACH or above at all times.

Inpatient pharmacy compounding uses ISO 5 for the critical zone and ISO 7 for the buffer zone, as specified in USP <797> [6].

Clinical laboratory testing areas may operate at ISO 7 or ISO 8, depending on the sample type and the sensitivity of the analysis. Where outcome data is available, facilities with properly maintained clean air systems report lower surgical site infection rates than conventional operating rooms.

Performance Validation & Routine Monitoring

Validation proves the cleanroom works as designed at commissioning, while ongoing monitoring proves it stays within limits during daily operation. Both are required, and both produce the documentation that regulators and auditors expect to see.

The validation sequence runs from installation qualification (IQ) through operational qualification (OQ) to performance qualification (PQ). Each stage produces test data, and each test follows a standard procedure.

Core Validation Test Procedures

Installation Qualification (IQ) verifies that equipment and systems are installed according to design specifications. Operational Qualification (OQ) confirms that systems operate within specified limits across the intended range. Performance Qualification (PQ) demonstrates that the cleanroom consistently meets its ISO class under real operating conditions.

The following tests are carried out during the PQ phase.

• Airborne particle concentration counting: samples at defined points and compares results against ISO 14644-1 limits.
• Airflow velocity measurement: verifies unidirectional flow at 0.3–0.5 m/s in critical zones.
• Pressure differential verification: confirms 10–15 Pa between adjacent grades using calibrated manometers.
• Filter leak integrity testing: DOP or PAO aerosol challenge with photometer scan, following iso 14644-3 [2].

These tests together confirm that the cleanroom performs to its design specification.

Routine Maintenance & Monitoring Schedules

Daily pressure differential checks are the first line of defense. A sudden pressure drop points to a door seal failure, a filter loading issue, or an HVAC fault. Quarterly particle count testing confirms the room still meets its ISO class. Annual filter integrity tests catch media damage or seal degradation.

Deiiang maintenance guidance aligns with these intervals. Filter replacement is triggered when final resistance reaches 400–600 Pa, or by a failed integrity test, whichever comes first.

Based on Deiiang field service experience, the following diagnostic checklist helps identify common issues.

Frequently Asked Questions

What ISO classification do most medical cleanrooms use?

Most medical cleanrooms operate at ISO 5, ISO 7, or ISO 8. ISO 5 is used for critical aseptic tasks. ISO 7 covers general sterile work and operating rooms, while ISO 8 supports packaging and less critical areas.

How often should HEPA filters be replaced in pharmaceutical cleanrooms?

Typical service life is 2–5 years, depending on particle load and operating hours. Annual integrity testing is the primary trigger for replacement. Deiiang catalogue data sets the final resistance range at 400–600 Pa, and pressure drop monitoring shows when that threshold approaches.

Why is positive pressure standard for medical cleanrooms?

Positive pressure prevents unfiltered external air from entering through gaps and door openings. It maintains contamination exclusion and supports aseptic conditions. The pressure cascade protects critical zones by keeping air flowing from clean to less clean.

Do hospital and pharmaceutical cleanrooms follow the same standards?

They share the ISO 14644 base standard for classification. Pharmaceutical cleanrooms follow strict GMP rules under EU GMP Annex 1 and FDA 21 CFR Part 211. Hospital cleanrooms follow infection control guidelines, with different monitoring frequencies and documentation requirements.

What is the minimum air change rate for an ISO 7 medical cleanroom?

A minimum of 60 ACH is typical for turbulent ISO 7 spaces. Critical zones under unidirectional flow operate at higher effective rates. Deiiang HVAC design benchmarks use 60 ACH as the baseline for ISO 7 and specify 20% minimum outdoor air.

How does contamination control differ for devices vs. drug products?

Drug products prioritize microbiological control. Devices add particulate control and often ESD protection. Packaging sterility requirements differ, and audit frequency varies by device classification and drug product type.

References

• [1] ISO 14644-1:2015 — Classification of air cleanliness by particle concentration. International Organization for Standardization.
• [2] iso 14644-3:2019 — Test methods for cleanrooms and associated controlled environments. International Organization for Standardization.
• [3] iso 14644-5:2004 — Operations in cleanrooms and associated controlled environments. International Organization for Standardization.
• [4] EU GMP Annex 1 (2022) — Manufacture of Sterile Medicinal Products. European Commission.
• [5] FDA 21 CFR Part 211 — Current Good Manufacturing Practice for Finished Pharmaceuticals. U.S. Food and Drug Administration.
• [6] USP <797> — Pharmaceutical Compounding — Sterile Preparations. United States Pharmacopeial Convention.
• [7] PIC/S GMP Guide — Pharmaceutical Inspection Co-operation Scheme.
• [8] GB 50073 — Code for Design of Clean Rooms. Ministry of Housing and Urban-Rural Development, China.
• [9] EN 1822 — High Efficiency air filters (EPA, HEPA and ULPA). European Committee for Standardization.
• [10] ISO 16890 — Air filters for general ventilation. International Organization for Standardization.