Technical reference
ISO 14644-1 classifications describe permitted concentrations of airborne particles measured under defined conditions. They do not describe finishes, equipment, or how a room looks.
Representative environment
Lower class numbers permit fewer airborne particles, so ISO Class 5 is cleaner than ISO Class 8. Higher-numbered classes are frequently the right answer — the goal is the class your process actually requires, not the lowest number available.
Each entry below summarises what the class describes, where it is typically applied, and what it usually means for construction. This is educational guidance, not a compliance document; verification always comes from testing performed by qualified parties.
Classes 1 through 9
Representative environment
Most stringent of the classifications defined in ISO 14644-1.
Typical use
Highly specialized research and semiconductor-adjacent processes with extreme sensitivity to sub-micron particles.
What it means for construction
Full filtration coverage, unidirectional airflow, and extremely tight envelope and penetration detailing. Every joint, fastener, and interface is a design decision.
Representative environment
Extremely low airborne particle concentrations.
Typical use
Advanced semiconductor, photonics, and specialized metrology environments.
What it means for construction
Unidirectional airflow with near-complete filter coverage, raised or perforated floor strategies, and rigorous construction protocol from first mobilization.
Representative environment
Very low airborne particle concentrations.
Typical use
Semiconductor and precision optics work, and selected aerospace and defense processes.
What it means for construction
High filter coverage, tightly controlled pressure cascade, and gowning sequences that separate the room from all adjacent space.
Representative environment
Low airborne particle concentrations with substantial filtration coverage.
Typical use
Precision electronics, optics assembly, and sensitive medical device processes.
What it means for construction
Flush gasketed ceiling systems, sealed penetrations, coved or integral-base flooring, and coordinated pass-through and airlock design.
Representative environment
A widely specified classification for critical processing zones.
Typical use
Medical device manufacturing, aseptic processing zones, pharmaceutical and biotechnology work, and precision assembly.
What it means for construction
Significant filter coverage, defined pressure relationships, gowning and material airlocks, and cleanable non-shedding surfaces throughout.
Representative environment
Moderately stringent airborne particle limits.
Typical use
Medical device assembly, electronics, and support space adjacent to more critical zones.
What it means for construction
Partial filter coverage with careful diffuser placement, sealed envelope construction, and controlled entry sequence.
Representative environment
A common classification for controlled production and support areas.
Typical use
Medical device manufacturing, packaging, aseptic support space, and precision assembly with moderate particle sensitivity.
What it means for construction
Filtered supply with defined air change rates, sealed ceilings and walls, coved flooring, and gowning at entry.
Representative environment
Controlled but less stringent airborne particle limits.
Typical use
Packaging, material staging, warehousing adjacent to controlled space, and general controlled manufacturing.
What it means for construction
Filtered air with lower change rates, cleanable finishes, sealed penetrations, and controlled entry with sticky mats or an anteroom.
Representative environment
Least stringent classification defined in ISO 14644-1.
Typical use
Controlled buffer, staging, and transition space supporting cleaner areas; light controlled manufacturing.
What it means for construction
Cleanable finishes, defined housekeeping, sealed transitions to cleaner areas, and pressure relationships that protect adjacent classified space.
ISO FAQ
Plain-language answers on what an ISO classification means, what Maydus is responsible for, and where independent testing and your quality system take over.
Our certification scope
Maydus constructs and delivers cleanroom environments designed around the ISO classification your process requires. Maydus does not independently provide ISO certification; required testing and third-party certification are coordinated as part of the project.
Where our responsibility starts and stops on a classified project, stated plainly.
No. Maydus constructs and delivers cleanroom environments designed around the ISO classification your process requires. We do not independently provide ISO certification. Required testing and third-party certification are coordinated as part of the project and performed by qualified independent parties.
Construction and coordination: the envelope and its integrity, wall and ceiling systems, sealed penetrations, cleanable flooring and transitions, filtration and HVAC coordination, electrical and controls infrastructure, construction-phase cleanliness protocol, and holding the schedule around commissioning and testing. If testing identifies a construction-related item, correcting it is on us.
An independent testing and certification provider, engaged either by you or coordinated by us on your behalf. Keeping testing independent of the builder is the point — the result is a measurement, not a self-assessment.
No responsible builder can guarantee a test result, because classification depends on design, commissioning, testing method, and how the room is operated, gowned, and maintained after handover. What we can commit to is building to the design intent for your target class, supporting commissioning and testing, and correcting construction-related deficiencies that testing finds.
Yes. Tell us the documentation you need — submittals, material certifications, construction protocol records, as-builts, closeout packages — and it is built into the project rather than assembled after the fact.
What an ISO class number means, and what it does not mean.
ISO 14644-1 classifications describe permitted concentrations of airborne particles at specified particle sizes, measured under defined conditions. A classification is a measured air cleanliness result — it is not a description of finishes, equipment, or how a room looks.
It is the opposite. Lower numbers permit fewer airborne particles, so ISO Class 5 is cleaner than ISO Class 8. Higher-numbered classes are frequently used for support, packaging, gowning, and transition spaces around a cleaner core.
They are the occupancy states a room can be tested in. As-built means complete but without equipment or people; at-rest means equipment installed and running with no personnel; operational means equipment running with people working normally. The same room can meet a class at rest and not in operation, so the state your requirement refers to matters as much as the number.
Not always. A controlled environment manages conditions such as particulate, temperature, humidity, pressure, or contamination without necessarily being classified to ISO 14644-1. Plenty of production spaces need control and cleanability without a formal class, and building one is a different scope than building the other.
How ISO 14644-1 relates to the regulatory requirements you may also carry.
ISO 14644-1 is a classification standard for airborne particulate. Regulatory frameworks such as FDA expectations, GMP, and USP chapters cover far more — procedures, monitoring, personnel, records, and product-specific controls — and often reference cleanliness classes within those larger requirements. Meeting a class is one input to compliance, not compliance itself. Your quality and regulatory team owns the framework; we build the space to support it.
That depends on your product, process, and market. Device manufacturers commonly work to ISO 13485 quality-system requirements and specify ISO 14644-1 classes for controlled processing areas. Tell us the requirement your quality team has issued and we build to it — we do not interpret regulatory obligation on your behalf.
Recertification intervals are driven by your classification, your quality system, and your regulator's expectations, not by the builder. Establish the interval with your certification provider and quality team, and design monitoring so the room can be tested without disrupting production.
Usually not. On active-facility work we isolate the area behind sealed containment held under negative pressure with filtered exhaust, so construction air is captured at the source. Adjacent classified and production space keeps operating while the work proceeds inside that envelope.
The questions that come up before a class, a scope, or a budget is settled.
That is common early on. Describe the process, the product, and any customer or internal requirements you have been given. Planning can proceed with a candidate range, and the envelope and mechanical scope can be priced across two options until the requirement is confirmed.
No. Classification performance is established through appropriate design, commissioning, testing, monitoring, and how the room is operated and maintained. Construction has to support those requirements through envelope integrity, airflow coordination, and cleanliness discipline, but the result is verified by testing — not by appearance.
The process and product, the target class and occupancy state if known, room size and ceiling height, required pressure relationships and gowning sequence, temperature and humidity ranges, process equipment and utilities, and any documentation your quality system requires. Gaps in that list are the main reason cleanroom budgets move after the fact.
Often yes, but the answer comes from the building, not the brochure. Structure, available ceiling height, mechanical capacity, power, and how the space connects to adjacent areas determine whether an upgrade is realistic or whether a new envelope inside the shell is the better path. We walk the space and tell you which one you are looking at.
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Start a conversation
Describe the process and any requirement you have been handed. We will tell you what still needs to be confirmed before a class and a budget are worth circulating.