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8 FACTORS TO CONTROL IN A CLEANROOM according to ISO 14644 and how to handle it

Updated: Dec 16, 2022

What is cleanroom inspection?

A cleanroom, as defined by ISO 14644-1, is a room in which the concentration of airborne particles is controlled and which is constructed and used in a structure such that the presence, production, and maintenance of particles in the room are reduced to a minimum and other factors in the room such as temperature, humidity, pressure can be controlled and controlled. When all factors in the room are controlled, it will help minimize the contamination or cross-contamination of products during research and production, ensuring sterility.

VAF™️ - VIET AIR FILTER supplies and installs electrical - clean room - air conditioning - ventilation systems for D PACK factory
VAF™️ - VIET AIR FILTER supplies and installs electrical - clean room - air conditioning - ventilation systems for D PACK factory

Cleanrooms are designed to ensure pollution control, including air movement control, air filtration, clean room construction, and cleaning and disinfection plans.

Cleanroom audits are quality system verifications and are also an integral part of GMP's good manufacturing practice. Cleanroom auditors must have specific knowledge and training in cleanroom operations and microbial contamination.

8 factors that need to be controlled in a clean room according to ISO 14644-1,2,3 and treatment and remedial plans

Check the pressure difference between the rooms

A room pressure difference is a difference in pressure between two measurement points in two different environments.

The pressure difference often does not meet the design given due to the following reasons:

  • The process of aligning the HVAC system between the inlet and return air (or exhaust) control valves.

  • Due to the openings of doors, windows, air vents, vent openings

Problem solution:

  • Adjust the supply and return (or exhaust) air valves between rooms so that the flow and pressure difference are guaranteed according to the design right from the system test run

Check wind speed, differential pressure, filter flow HEPA

Wind speed, filter flow, and filter differential pressure will be different and not meet the test requirements for the following reasons:

  • Adjust the air valve (VCD) supplied to each Hepa box;

  • The location of the filter is relative to the outlet of the air handling unit.

Problem solution:

  • Adjust the air supply valve so that filters of the same size are equivalent in terms of flow as well as surface wind speed;

  • Check whether the equipment's parameters have enough capacity, flow, and head to take appropriate measures to improve, supplement or replace;

  • Check and replace the filter periodically. If the time is up or the pressure difference exceeds the recommended pressure difference, the filter must be replaced with a new one;

  • Check, and replace torn Hepa filter by using testing equipment yourself or by a qualified and experienced testing unit;

  • Is the calculated filtration system adequate for the volume of the rooms? If there is no need to have the plan to renovate the equipment provided.

Check the visual direction of the airflow

Visual inspection of airflow is often unsuccessful because the supply and return valve adjustments are not open or less likely to fail in the flow direction.

Problem solution:

  • Open the supply and return air valves properly, marked on the valve when it is aligned.

  • It is necessary to check and replace the filter periodically and regularly because when the filter reaches the replacement time, it will lead to low or no air supply and return (or exhaust), leading to diffused gas flow elsewhere. or no airflow in the cleanroom;

  • Check if the supply and return air intakes (or exhaust air) are properly arranged – The best direction of airflow is from above. If it is not reasonable, there should be an improvement plan.

Cleanroom resiliency

Cleanroom recovery is a time-tested process of returning from a lower-grade clean environment to design cleanliness.

The cleanroom recovery test was not achieved according to the initial criteria given because:

  • Hepa filter leak leads to uncontrolled dust particles according to ISO 14644-1;

  • Due to the low number of wind exchanges, the recovery time is long

Problem solution:

  • The recovery factor depends on the number of air exchanges and the Hepa level of filtration should always ensure that the number of air exchanges is sufficient for a favorable recovery measurement.

  • Check the Hepa filter for leaks periodically as recommended every 12 months or replace the filter periodically according to the manufacturer's recommendations.

  • Check whether the HEPA filter is at a suitable level for the clean room level. For example, an ISO 5 (Class 1,000) clean room should use a Hepa H14 filter or better U15) if it is unreasonable to use a Hepa H13 filter and a computational alternative that meets the requirements of the room is required. clean.


The design failure is due to:

  • The capacity of the supply air handling unit is not enough

  • Due to the unbalanced arrangement of the vents, the temperature is different at many points;

  • Due to improper temperature setting


Design failure is due to:

  • Insufficient cooling capacity design;

  • Design the percentage of fresh wind is too much and the humidity outside the environment is very high;

  • Due to the humidity treatment equipment not working or not having enough capacity to respond to the flow.

The solution to the problem of temperature and humidity:

  • Check if the temperature setting of the device is running at full load, if it does not meet the full load, check if the system has lost any cooling load. (due to an open or broken hose)

  • If the load is not enough according to the design, there must be an alternative or upgrade plan.

  • The temperature and humidity settings are closely related to each other through the heating resistor, you must make sure that the calculated power is correct and reasonable.

HEPA filter leak

  • Filter leak (leak) during transportation, and installation;

  • The Hepa box and the details are not strong enough to be able to install the Hepa filter, causing the contact point between the Hepa filter and the box wall to have a gap that causes leakage ...

  • Solution: Leakage occurs in 02 locations, in the filter membrane or the contact point between the Hepa filter and the Hepa box.

  • For broken Hepa filters, measures must be taken to replace the HEPA filter.

  • If there is a leak in the contact area, it is necessary to determine the specific cause that may occur such as a Broken gasket, a leaky box (due to manufacturing or installation errors), not cleaning the filter box carefully, and the filter mounting pass has not been properly cleaned. tightened, improperly installed filter, ...

HEPA filter products of VAF™️ - VIET AIR FILTER


  • Due to poor cleaning of the clean room;

  • Not running the system after cleaning;

  • Hepa filter leak, tear;

  • Design calculations for the low number of air exchanges

Problem solution:

  • To meet the requirements, first of all, must check the installation of the Hepa filter, check for leaks, and check the design for capacity and number of air exchanges... Cleaning and commissioning of the HVAC system for 24 hours before the measurement is extremely important and necessary.

Thus, the factors affecting the quality of clean rooms can be attributed to two main groups of causes: technical errors such as errors in system design and system operation; Second, during use, it is necessary to check and replace the HEPA filter periodically to achieve optimal performance of the design.

In addition, the design may be different from the actual process of demand and expansion, so the equipment does not meet the cooling capacity, flow, pressure head, etc., it is necessary to have a plan for measurement and calculation based on the basis practical basis to come up with a reasonable alternative and complementary solutions. Customers contact VAF™️ - VIET AIR FILTER at hotline 1900 8949 or fanpage to register for free consultation and survey.


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