Classification and basic criteria for inspecting of clean room

Every cleanroom requires periodic testing to ensure that the allowable particle count required for cleanroom classification is achieved. The cleanroom is initially certified upon completion of acceptance and then needs to be re-inspected every 6 to 12 months to ensure the cleanroom continues to comply with the strict requirements of cleanroom standards.

Clean room certification is periodically checked by an independent unit to ensure it meets the required ISO level. For medical device and pharmaceutical factories, inspection is for compliance with GMP or FDA certification. For semiconductor, aerospace and other industries, clean rooms are essential to ensure productivity and product quality.


ISO 14644-1 Cleanroom Standards | Cleanroom Classifications

Class Maximum Particles/m³ Fed STD 209E
> 0,1 um > 0,2 um > 0,3 um > 0,5 um > 1 um > 5 um
ISO 1 10 2.37 1.02 0.35 0.083 0.0029
ISO 2 100 23.7 10.2 3.5 0.83 0.029
ISO 3 1.000 237 102 35 8.3 0.29 Class 1
ISO 4 10.000 2.370 1.020 352 83 2.9 Class 10
ISO 5 100.000 23.700 10.200 3.520 832  29 Class 100
ISO 6 1.000.000 237.000 102.000 35.200 8.320 293 Class 1.000
ISO 7 352.000 83.200 2.930 Class 10.000
ISO 8 3.520.000 832.000 29.300 Class 100.000
ISO 9 35.200.000 8.320.000 293.000 Normal room

Table 1. ISO-14644-1 Clean Room Classes


  • Clean room classification standards include the number of particles and the number of air exchanges per hour. Other parameters commonly tested as part of cleanroom certification include: room pressure, temperature, humidity, particle count, room brightness, and noise level.
  • ISO document 14644-2, Cleanroom Inspection and Compliance, states that all cleanrooms regardless of classification level must be regularly quality tested. Particle count testing must be performed annually for ISO class 6 or higher cleanrooms or every six months for ISO class 5 or lower cleanrooms.
  • There are also US FED STD 209E cleanroom classes that measure particles per cubic foot but are also equivalent to ISO-14644-1 classes.

US FED STD 209E Cleanroom Standards | Cleanroom Classifications

Class Maximum  Particles/ft³ ISO equivalent
> 0,1 um > 0,2 um > 0,3 um > 0,5 um > 5 um
 1 35 7 3 1 ISO3
 10 350 75 30 10 ISO4
100 100 ISO5
1000 1000 7 ISO6
10.000 10.000 70 ISO7
100.000 100.000 700 ISO8

Table 2. FED STD 209E cleanroom classification


  • Check for filter leaks: An important requirement when completing room cleaning is HEPA/ULPA filter leaks. Typically, filter leak testing is measured using an optical particle counter to evaluate filter efficiency results based on the inlet and outlet particle counts of the HEPA/ULPA filter.
  • Check air exchange times: Another requirement for both ISO and FED STD cleanroom classifications is the number of HEPA/ULPA-filtered air changes per hour.
  • The individual air flow rate from each HEPA fan filter can be measured using an airflow hood.
  • Testing laminar or turbulent air flow: To evaluate the shape of laminar or turbulent air flow, the smoke test method is often used, a certain amount of specialized smoke will be released at the air supply part of the HEPA/ULPA filter fan to evaluate the direction of the air flow, thereby determining whether the air flow is straight (laminar flow) or flowing in many different directions (turbulent flow).
  • Microbiological testing is for living organisms. Typically, samples are collected using settling plates with some type of medium. The plates are placed in the clean room at specific locations for 4 hours and then sent to the analytical laboratory for incubation. and measurement.
  • Temperature and humidity checks are performed using a digital thermometer and hygrometer that meets the quality standards of the Institute of Standards and Metrology.
  • Light testing is usually performed using a light meter in the form of a grid. Clean room testing is testing the luminous flux (lumens) per square meter (LUX).
  • Noise testing is performed using a sound level meter in the form of a grid, in decibels.

Frequency of clean room inspection

Most companies perform 3rd party cleanroom inspections annually and perform internal inspections quarterly or monthly. Frequency depends on the company’s manufacturing processes, ISO-9001 procedures, customer requirements or CGMP/FDA validation documents.

Your cleanroom should be periodically inspected to ensure the required allowable particle counts are being achieved and effectively maintaining a clean, controlled environment. If you are concerned that your cleanroom does not achieve the required particle count for the ISO class, talk to a cleanroom expert who will investigate and come up with a solution for your situation.


FFU Fan Filtration Unit – TECRA.FFU

FFU fan filtration units are commonly used to control contamination in pharmaceutical manufacturing, medical devices, healthcare facilities, and test or laboratory environments.

Ready-to-use products for clean room microbiological testing methods

Rodac/Contact Plate

Basic nutrient medium for cultivating many types of microorganisms for surface microbiological sampling.


Used for surface collection and inspection.

Petri 90mm

Basic nutritional environment for cultivating many types of microorganisms and fungi.


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