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The key elements of cleanroom design and construction
2025/10/29
Its design and construction need to take into account pollution control, functional adaptation, compliance and operational economy. The core key elements can be classified into the following categories:
1）. Core Parameters:
The design of a cleanroom must first clarify the cleanliness grade, which serves as the foundation for all designs and directly determines subsequent processes such as air treatment and material selection. Different industries follow different standards and need to be matched specifically
International standard: Centered on ISO 14644-1, grades are classified based on the number of particles ≥0.5μm in each cubic meter of air (for example, ISO Level 5 corresponds to ≤3,520 particles /m³, and ISO level 8 corresponds to ≤ 3.52 million particles /m³). Industry-specific standards: Pharmaceutical industry: Compliance with GMP (such as China GMP, EU GMP) is required. Besides particle control, strict control of microorganisms (sedimentation bacteria, airborne bacteria) is also necessary. In some scenarios, sterility is required (such as injection workshops). Electronics industry: Adhering to SEMI standards, with a focus on controlling ultra-small particles (≤0.1μm) and static electricity to prevent chip oxidation or short circuits; Medical industry: Complies with YY 0033 (Hospital Clean Operating Department Standard), and requires simultaneous control of biological load and cross-infection risk.
2）. Air Treatment System
The core function of a cleanroom, which is the "heart" of pollution control, is to control pollutants through air filtration and air flow organization. Therefore, the air treatment system is the key to design.
1. Filtration system: Staged filtration, precise dust control
Filtration levels: It needs to go through three levels of filtration: "primary efficiency → medium efficiency → high efficiency/ultra-high efficiency" to remove particles and microorganisms in the air. Primary efficiency filter: Intercepts large particles ≥5μm (such as dust and hair) to protect subsequent filters. Medium-efficiency filter: Intercepts 1-5μm particles (such as pollen and some microorganisms); High-efficiency filter (HEPA) : Intercepts particles ≥0.3μm (filtration efficiency ≥99.97%), used in ISO 5-8 cleanrooms; Ultra-high Efficiency Filter (ULPA) : Intercepts particles ≥0.12μm (filtration efficiency ≥99.999%), used in ISO 3-4 grades (such as chip lithography workshops). Filter installation: Strict sealing is required (such as using liquid groove sealing or gel sealing) to prevent the leakage of unfiltered air. At the same time, reserve space for replacement to facilitate later maintenance.
2. Air flow organization: Directional pollution control to avoid dead corners
The form of air flow directly affects the diffusion and discharge of pollutants. It should be selected based on the cleanliness grade and function:Unidirectional flow (laminar flow) : Air flows at a uniform speed (0.3-0.5m/s) in a single direction (vertical or horizontal), which can quickly carry away contaminants and is suitable for high-cleanliness scenarios (ISO 3-5 levels, such as operating rooms and chip packaging areas). Non-unidirectional flow (turbulent flow) : Air diffuses and mixes after passing through the filter, and pollutants are diluted by the number of air changes. It is suitable for low cleanliness scenarios (ISO 6-9 levels, such as food packaging areas and medical device assembly areas). Mixed flow: Unidirectional flow is used in the core area and non-unidirectional flow in the periphery, taking into account both cleanliness and economy (such as in pharmaceutical filling workshops). 3. Air change rate: Enhance the dilution of pollutants
Determined according to the cleanliness grade:
ISO Level 5 (100) : ≥240 times per hour; ISO Level 6 (1000 level) : ≥60 times per hour; ISO Level 7 (100,000 grade) : ≥30 times per hour; ISO Level 8 (300,000 grade) : ≥15 times per hour.
3）. Spatial Layout and Circulation Design
To avoid cross-contamination in cleanrooms, it is necessary to reduce the contaminants brought in by personnel and materials through reasonable zoning and flow line planning. The core principle is "gradually transition from low-cleanliness areas to high-cleanliness areas to avoid backflow."
1. Zoning design: Divided according to the cleanliness gradient
Typical zones include (increasing cleanliness from the outside to the inside) :
Non-clean areas: such as offices and warehouses; Auxiliary clean areas: such as changing areas (first change, second change), buffer rooms, air shower rooms (for removing surface particles of personnel); Core clean areas: such as production areas and laboratory areas (which need to be subdivided according to the process, such as the batching area and filling area in a pharmaceutical workshop). 2. Flow line planning: Separation of people flow, material flow and waste flow
People flow: You need to go through the procedures of changing clothes (into clean suits), washing hands, and air shower to enter the core area. Do not enter directly wearing non-clean suits. Logistics: Materials are transferred through transfer Windows (with ultraviolet disinfection or interlock functions) and air lock rooms to prevent external contamination from entering when the door is opened. Waste flow: Set up dedicated channels to promptly remove waste (such as pharmaceutical waste and laboratory garbage) and prevent dust accumulation.
4）. Enclosure Structure
Physical barriers and anti-pollution base enclosure structures (walls, floors, ceilings, doors and Windows) must meet the requirements of "no dust generation, no dust accumulation, easy cleaning, and good sealing" to avoid becoming pollution sources themselves.
Wall: Stainless steel plates, color steel plates (double-sided galvanized) or epoxy resin coating are used. The joints are treated with sealant to prevent dust accumulation. The corner of the wall is designed as a rounded corner (radius ≥50mm), which is convenient for cleaning and has no hygiene dead corners. Floor: Commonly used are epoxy resin self-leveling (resistant to chemical corrosion and easy to clean), PVC rolls (anti-static, suitable for the electronics industry) or stainless steel floors (heat-resistant and disinfected, suitable for the pharmaceutical industry), which need to be sealed with the wall to prevent liquid penetration. Ceiling: Made of the same material as the wall, it needs to support FFU (Fan Filter Unit), lighting fixtures and other equipment, and be tightly sealed to prevent unclean air from the top from seeping in. Doors and Windows: Double-layer tempered glass is adopted (with good visibility). The doors are automatic sensor doors or manual sliding doors, equipped with door closers to ensure sealing after closing. Windows need to be fixed to prevent contamination from being introduced when they are opened.
5）. Environmental Parameter Control
In addition to cleanliness, temperature, humidity and pressure differences are the keys to maintaining the stability of a cleanroom and need to be precisely controlled according to industry requirements.
Temperature: The electronics industry typically requires 22±2℃ (to avoid thermal expansion and contraction of chips). Pharmaceutical industry: 18-26℃ (to ensure personnel comfort and material stability); Humidity: 50±5% for the electronics industry (anti-static, to prevent components from getting damp); Pharmaceutical industry: 45-65% (To prevent microbial growth and avoid powder materials absorbing moisture and caking); Pressure gradient: The core clean area should maintain positive pressure (to prevent the infiltration of low-clean air from the outside, such as in electronic and food workshops), with a pressure difference of ≥5Pa. Areas that need to be isolated from contamination (such as biosafety laboratories and infectious disease wards) should maintain negative pressure with a pressure difference of no less than 10Pa to prevent the spread of internal contaminants.
6）. Facilities and Equipment:
Facilities and production equipment in clean rooms should comply with the principles of "low dust generation, easy cleaning, and corrosion resistance".
Clean auxiliary equipment: such as clean workbenches (local high cleanliness), FFU (flexible adjustment of area cleanliness), transfer Windows (double doors interlocked to prevent air flow), clean wardrobes (for storing clean suits, with built-in ultraviolet disinfection). Production equipment: Stainless steel material (such as pharmaceutical reaction vessels) should be selected, with a smooth surface and no dead corners. Materials that are prone to paint peeling or detachment should be avoided. When the equipment is in operation, the emissions of dust and exhaust gas should be reduced (local exhaust devices should be installed if necessary). Pipelines and lighting fixtures: Water and electricity pipelines should be concealed (to prevent dust accumulation), and sealed clean lamps (such as recessed LED lamps) should be selected for lighting fixtures to avoid glare and dust emission.
7）. Construction and Acceptance：
Ensure the implementation of design and construction control: The construction environment needs to be cleaned in advance, and dust removal is required before materials enter the site. The sealing of joints between walls and floors must be strictly inspected (such as using smoke to test the sealing performance). After the filter is installed, a leak detection (such as scanning to detect the HEPA leakage rate) is required. Acceptance criteria: In accordance with ISO 14644-2 (performance testing) or industry standards (such as GMP appendices), parameters such as suspended particle concentration, settled bacteria, surface microorganisms, air flow velocity, pressure difference, temperature and humidity shall be tested. Only after all meet the standards can it be put into use.
8）. Operation and Maintenance：
When maintaining long-term clean design, maintenance convenience should be reserved
The filter should be easy to replace (such as by setting up a maintenance passage), and the resistance should be monitored regularly (replaced in time when the resistance exceeds the standard). Establish cleaning and disinfection procedures (such as wiping surfaces with 75% alcohol daily and regularly disinfecting with formaldehyde fumigation or hydrogen peroxide atomization); Personnel management: Training is required before entering the clean room (such as correctly putting on and taking off clean suits and avoiding rapid movement to generate dust), and unauthorized personnel are restricted from entering.
In conclusion, the design and construction of cleanrooms should focus on "pollution control", integrating industry demands, functional scenarios, and compliance standards. The entire process from parameter determination, system design, material selection to construction acceptance should be strictly controlled. At the same time, both operational economy and maintenance convenience should be taken into account to achieve a long-term and stable clean environment.
