Cleanroom and HVAC Knowledge
What is a cleanroom?
The meaning of a cleanroom, as defined in ISO 14644-Classification of Air Cleanliness by Particle Concentration,
refers to a room where dust or particle levels are controlled to not exceed the concentration limits specified by the standard. Additionally, the processes of design, construction, and operational practices are managed to minimize the generation and accumulation of particles within the room. Environmental parameters such as temperature, humidity, and room pressure are also controlled, along with other requirements, such as lighting levels, vibration, and static electricity.
6 Key Factors for Ensuring an Efficient Cleanroom System
Type, Category, and Material Shape: Materials used for walls, floors, and other construction elements.
HVAC System Design: Proper design of heating, ventilation, and air conditioning systems tailored for cleanroom applications, including air filtration, temperature, and humidity control.
Pressure Control: Build and maintain pressure differences in each area.
Air Change Rate (ACR): Ensuring appropriate air circulation rates for cleanliness levels.
Operational Practices: Strict control over personnel entering, exiting, and working within the cleanroom.
Maintenance and Cleaning: Regular maintenance of systems and consistent cleaning of the cleanroom environment.
14644-1 ISO Classes of air cleanliness by particle concentration
ISO Classes of Air Cleanliness by Particle Concentration refers to the "level of air cleanliness according to ISO standards based on the concentration of particles in the air." It is a standard that defines the level of air cleanliness in controlled environments (such as cleanrooms) according to the number of particles present in the air at specific sizes, such as 0.1 micron, 0.5 micron, etc. This standard is widely used in industries such as:
Microelectronics
Pharmaceutical or biopharmaceutical manufacturing
Hospitals
Food production
Examples of ISO Classes:
ISO 1: The highest cleanliness level (minimum number of particles)
ISO 5: Cleanroom class standard for pharmaceutical grade A (Cleanroom Class 100)
ISO 9: Environment close to that of typical indoor conditions
Particle Size Definition A 0.5 micron particle refers to the size of the particles in the air that are counted or measured in air cleanliness measurement tables. Particles smaller than 1 micron are commonly found in industries that require highly controlled air, such as electronic component manufacturing or pharmaceutical production.
ISO Class Definition ISO 6 refers to the level of air cleanliness where the number of 0.5 micron particles is limited within a specified volume of air. For example, the particle count may be measured in 1 cubic meter (1 m³) of air. ISO 6 is one of the classes used in cleanrooms, and this standard defines the maximum number of particles allowed in the air within a controlled space.
Reading the Table An ISO Class table
Example reading: In ISO Class 6, the number of 0.5 micron particles per 1 cubic meter of air is limited to 35,200 particles (according to ISO 14644-1). This means that in 1 cubic meter of air, there should not be more than 35,200 particles of 0.5 microns to maintain the ISO 6 cleanroom standard.
The key criteria for classifying air cleanliness according to ISO 14644-1 include:
Particle Concentration: The classification is based on the maximum allowable concentrations of airborne particles of specified sizes (e.g., 0.1 μm, 0.2 μm, 0.3 μm, etc.) in a defined volume of air. The standard defines nine ISO classes (from Class 1 to Class 9) with specific limits for particle concentrations , .
Cumulative Concentration: The concentrations listed in the classification tables are cumulative, meaning that the allowable number of particles for a given size includes all particles of larger sizes. For example, for ISO Class 5, the concentration for 0.3 μm includes all particles equal to and greater than that size .
Testing Procedures: Compliance with the specified cleanliness class is verified through standardized testing procedures, which include the selection of sampling locations and methods for measuring particle concentrations .
Clean Zone Definition: A clean zone is defined as a controlled space where the number concentration of airborne particles is managed and classified. This space is constructed and operated to minimize the introduction and retention of contaminants .
Monitoring and Compliance: Regular monitoring and testing are required to ensure that the air cleanliness levels remain within the specified limits. This may involve periodic classification based on risk assessments and continuous monitoring if appropriate instrumentation is in place .
Example of Designing a Layout for a Medium-Sized Cleanroom
This example is for general applications, which may require additional details and specifications tailored to each industry. These may include temperature, humidity, pressure in each zone, as well as additional details for each area, such as size, location, and quantity, based on necessity and suitability for the workflow.
What is ASHRAE ?
ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) is a professional association for heating, ventilation, air conditioning, and refrigeration engineers in the United States, internationally recognized. Currently, ASHRAE standards and practices are used in over 130 countries worldwide, with the goal of developing technologies to save energy, improve efficiency, and protect the environment, such as ASHRAE Standards and ASHRAE Handbooks.
Examples of some widely used standards in work include:
ASHRAE Standard 62.1 – Ventilation for Acceptable Indoor Air Quality
A standard for ventilation in commercial and institutional buildings to ensure acceptable indoor air quality.ASHRAE Standard 62.2 – Ventilation and Acceptable Indoor Air Quality in Residential Buildings
A standard for ventilation in residential buildings.ASHRAE Standard 55 – Thermal Environmental Conditions for Human Occupancy
Used to define thermal comfort conditions in building spaces, such as temperature, humidity, and air velocity.ASHRAE Standard 170
A standard for ventilation in healthcare facilities such as hospitals, clinics, or operating rooms, focusing on controlling air quality to prevent infections and maintain a safe environment for patients and medical staff.ASHRAE Standard 90.1 – Energy Standard for Buildings Except Low-Rise Residential Buildings
Used in design to save energy in commercial buildings.ASHRAE Handbook Series
A series of handbooks covering essential topics such as HVAC Applications, Fundamentals, and Systems and Equipment.
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