Cleanroom ISO classes: how to read ISO 14644

What ISO 14644 is

ISO 14644 is the international series of standards for cleanrooms and controlled environments. Part 1, ISO 14644-1, sets how air cleanliness is classified by particle concentration. Part 2, ISO 14644-2, covers monitoring: how you show over time that the room still meets its class. Both parts were revised in 2015.

The classification table: how many particles each class allows

Classes run from ISO 1, the cleanest, to ISO 9. Each class allows ten times as many particles as the one before it. The table shows the maximum number of particles of 0.5 µm and larger per cubic metre of air, the size most often used for comparison, and the matching name in the old US standard.

The standard also has columns for other sizes, from 0.1 to 5 µm, and each room is classified at the sizes specified for it. A full classification therefore states the particle size and the occupancy state at the time of testing, for example: ISO 7, at rest, at 0.5 µm.

Class 100 and Class 10,000: where the old names come from

Before ISO 14644, cleanrooms were classified under the US standard FED-STD-209E. It counted particles of 0.5 µm and larger per cubic foot, and the class name was the maximum count: Class 100 allows up to 100 particles per cubic foot, about 3,520 per cubic metre, which is ISO 5. The standard was cancelled in November 2001 and replaced by ISO 14644, but many people and suppliers still say Class 100 or Class 10,000, so it helps to know both systems.

EU GMP grades A, B, C and D

Pharmaceutical plants and sterile manufacturing work to EU GMP Annex 1, which uses grades A to D. Each grade is defined in two states: at rest and in operation. By the concentration of 0.5 µm particles, the grades line up with these ISO classes:

Which state is tested: as-built, at-rest, operational

The standard distinguishes three occupancy states:

• As-built: the room is complete and the air systems are running, but there is no equipment and no one inside.
• At-rest: equipment is installed, but there is no one in the room.
• Operational: the room is working normally, with its equipment and the agreed number of people.

The same room can meet ISO 5 with no one inside and fail it during work, because people and movement add particles. That is why a classification has to state which state the room was tested in. New equipment brought into the room also changes the picture, which is one reason rooms are tested again after a move.

When the room is tested again

Under ISO 14644-1, classification is repeated at intervals set by risk assessment, typically once a year. In rooms that work to Annex 1, grades A and B are requalified at least every 6 months, and grades C and D at least every 12 months.

Besides periodic testing, Annex 1 also calls for requalification after changes, for example:

• An interruption of airflow that affects how the room operates.
• A change to the room's design or to the HVAC settings.
• Special maintenance, such as replacing the final filters.

Testing usually covers particle counts, filter integrity, airflow volume and velocity, and pressure differences between rooms. A qualified tester working for the room's owner carries it out, and QA decides which tests are needed after each change.

What this means when equipment moves in or out

The class also sets how the move is done. The cleaner the room, the stricter the procedure: how equipment is cleaned and wrapped before it goes in, which airlock it passes through, what the crew wears and how many people may enter. Before a move we ask the cleanroom team for the class and the entry procedure, and plan packing, crew and sequence around them. The steps themselves are in our guide Moving equipment into and out of a cleanroom.

Every door opening and every item brought in raises the particle count. Leave time in the schedule for cleaning and testing before work resumes, and if the air system is switched off or the room is altered during the works, book requalification in advance as well.

What the customer is responsible for

We plan the move, pack to the room's procedure, and transport and position the equipment. Cleaning the room, testing and classification are done by your QA team or by a qualified testing company you appoint, and we coordinate the schedule with them so testing can start right after positioning.

More on cleanrooms

• Moving equipment into and out of a cleanroomHow to move equipment into a cleanroom: clean and double-bag, enter through the airlock, gown the crew correctly and run classification tests after.
• Portable cleanrooms: what they are and how to move onePortable and modular cleanrooms: softwall vs hardwall, which ISO class they reach, and how to move one within a building or relocate it to a new site.
• Moving a laminar flow cabinetHow to move a laminar flow cabinet (clean bench): protecting the HEPA filter, removing the stand, upright shock-free transport, and airflow and filter integrity testing before work resumes. Plus how it differs from a biosafety cabinet.

Lab moving by area

• Lab relocation in Rehovot, Ness Ziona and the Science Park
• Lab moving in Tel Aviv, Herzliya and Petah Tikva
• Lab and medical equipment moving in Jerusalem
• Lab and industrial moving in Haifa and the north
• Lab moving in Yokneam, Migdal HaEmek and the Galilee
• Lab moving in Beer Sheva and the south
• Lab and medical equipment moving in the Sharon
• Lab moving in Caesarea
• Sensitive equipment and industrial moving in Kiryat Gat and Ashkelon

More guides

• Lab relocation checklist: 15 steps before, during and afterA practical lab relocation checklist: appoint an owner, map equipment, handle chemicals and samples separately, and verify everything after the move.
• Moving analytical instruments: HPLC, mass spectrometers and GCHow to move analytical instruments without damage: preparing HPLC, mass spectrometers and gas chromatographs for transport, packing, air-ride transport and getting back to work.
• Moving an electron microscope: what to knowHow to relocate an electron microscope: work with the manufacturer's engineer, secure the column, move without vibration and prepare the new room.
• Insurance when moving expensive equipment: what to checkWhat to check about insurance before moving expensive equipment: coverage amount, exclusions, documentation before the move and how to report damage.