Foreword

There is a close, synergistic relationship between the architectural layout of a cleanroom and its air purification and HVAC system. The design of the purification system relies on the overall architectural layout as a prerequisite, while the planning of the architectural space must adhere to the technical principles of the purification system. Only through such mutual compatibility can the cleanroom’s various functions operate efficiently. Consequently, designers of purification systems must not only possess a deep understanding of the architectural spatial structure to optimize system configuration but also articulate professional requirements regarding the layout from the perspective of air cleanliness control, ensuring full compliance with cleanroom design standards. In the following sections, we will provide a systematic analysis of key considerations for cleanroom layout.

1. Floor Plan Layout of Cleanrooms

Cleanrooms generally consist of three main sections: the clean zone, the semi-clean zone, and the auxiliary zone. The floor plan layout of a cleanroom can be arranged in several ways:

1. Outer Corridor Layout

The outer corridor may be designed with or without windows and serves dual purposes: as a viewing area and a space for housing certain equipment; in some cases, heating systems are installed within the corridor for standby use. External windows must be of the double-glazed, airtight type.

2. Inner Corridor Layout

The cleanroom is situated along the perimeter, while the corridor is located centrally. Corridors in this configuration typically maintain a high cleanliness class, often matching that of the cleanroom itself.

3. Dual-Side Layout

The clean zone is located on one side, while the semi-clean and auxiliary rooms are situated on the other.

4. Core Layout

To conserve land and minimize pipeline lengths, the clean zone is positioned as the core, surrounded on all sides—including above and below—by auxiliary rooms and spaces for concealed utilities. This configuration isolates the clean zone from external weather conditions, reduces heating and cooling energy consumption, and promotes overall energy efficiency.

II. Personnel Purification Route

To minimize the risk of contamination to the clean zone environment caused by personnel activity, individuals must change into cleanroom garments and undergo air showering, showering, and disinfection before entering the clean zone. These measures constitute "personnel purification" (often abbreviated as "personnel prep").

Supply air must be provided to the room within the personnel purification suite where cleanroom garments are changed; this room must maintain positive pressure relative to adjacent areas such as the entrance, as well as slight positive pressure relative to the toilets and shower areas, while the toilets and shower areas themselves must be maintained under negative pressure.

III. Material Purification Route

All items must undergo a purification process—referred to as "material purification"—before being introduced into the clean zone.

1. The material purification route must be kept separate from the personnel purification route. If materials and personnel must enter the cleanroom via the same location, separate entry points are mandatory, and materials must first undergo preliminary purification.

2. For operations that do not rely on a continuous production line, an intermediate storage area may be established along the material route.

3. For operations with a strong continuous production line, a direct-flow material route is adopted; in some cases, multiple purification and transfer facilities may need to be installed along this route.

4. Regarding system design, the preliminary and fine purification stages of the material purification area generate significant airborne particulates; therefore, these areas should maintain negative or neutral pressure relative to the clean zone. If the risk of contamination is high, negative pressure should also be maintained relative to the entry side.

IV. Utility Distribution

Utility systems in cleanrooms are highly complex; therefore, concealed distribution methods are employed. Specific concealed distribution methods include the following:

1. Technical Interstitial Spaces (Plenums)

Overhead technical interstitial space. Supply and return air ducts typically have the largest cross-sections and are thus the primary consideration for layout within this space; they are generally positioned at the top, with electrical conduits located beneath them. If the floor structure of the interstitial space can support the load, equipment such as filters and exhaust units may be installed there.

Room-level technical interstitial spaces. Compared to having only an overhead interstitial space, this method reduces the complexity and height requirements of the distribution layout and eliminates the need for vertical return air shafts connecting to the upper interstitial space. The lower interstitial space can accommodate return air fans, power distribution equipment, and the like. Additionally, the upper interstitial space of a cleanroom on one floor can serve as the lower interstitial space for the cleanroom on the floor above.

2. Technical Shafts/Chases (Wall-integrated)

Horizontal utility lines from the upper and lower interstitial spaces often need to transition to vertical runs; the concealed spaces housing these vertical lines are known as technical shafts or chases. These spaces can also accommodate auxiliary equipment unsuitable for the cleanroom environment, serve as return air ducts or plenums, and sometimes house bare-tube radiators.

Since these technical shafts (or wall-integrated chases) typically utilize lightweight partitions, they can be easily modified when process requirements change.

3. Technical Utility Shafts

While technical chases (or wall-integrated shafts) generally do not span multiple floors, technical utility shafts are used when vertical routing across floors is required. These shafts often form part of the permanent building structure.

Because technical utility shafts connect multiple floors, fire safety measures are essential. Once internal utilities are installed, floor penetrations must be sealed with fire-resistant materials that meet or exceed the fire rating of the floor slab itself. Maintenance is conducted on a floor-by-floor basis, and access points must be equipped with fire-rated doors.

Whether utilizing technical interstitial spaces, technical chases, or technical utility shafts, if the space doubles as an air duct, its interior surfaces must meet cleanroom standards...

V. Location of the Mechanical Room

Ideally, the air conditioning mechanical room should be located close to the cleanroom requiring a high air supply volume to minimize ductwork length. However, to prevent noise and vibration, the cleanroom and the mechanical room need to be separated. Both factors must be taken into account. Methods of separation include:

1. Structural Separation Methods

(1) Settlement joint separation: A settlement joint is positioned between the cleanroom and the mechanical room to act as a separator.

(2) Cavity wall separation: If the mechanical room is adjacent to the cleanroom, they do not share a common partition wall; instead, each has its own wall, with a gap of a certain width left between them.

(3) Auxiliary room separation: An auxiliary room is placed between the cleanroom and the mechanical room to serve as a buffer zone.

2. Decentralized Methods

(1) Rooftop or ceiling-space decentralization: Mechanical rooms are often located on the uppermost roof level to distance them from the cleanroom below; however, the floor directly beneath the roof should ideally serve as an auxiliary/administrative area or a technical interstitial space.

(2) Underground decentralization: The mechanical room is located in the basement.

3. Independent Building Method

The mechanical room is constructed as a separate building outside the cleanroom facility, though it should ideally be located in close proximity to the cleanroom. Attention must be paid to vibration and noise isolation for the mechanical room; the floor requires comprehensive waterproofing and adequate drainage measures.

(1) Vibration isolation: Vibration-dampening measures should be applied to the supports and bases of vibration sources such as fans, motors, and water pumps. If necessary, equipment should be mounted on a concrete slab supported by vibration-isolating materials; the weight of this slab should be two to three times the total weight of the equipment.

2. Sound isolation: In addition to installing silencers within the system, large mechanical rooms may utilize sound-absorbing materials on the walls and must be equipped with sound-insulating doors; under no circumstances should a door be installed in the partition wall separating the mechanical room from the clean area.

VI. Emergency Egress

As cleanrooms are highly airtight structures, emergency egress is a critical issue that is closely linked to the configuration of the air purification and HVAC systems. In general, the following points should be considered:

1. Each fire compartment or clean zone within a production area must have at least two emergency exits; a single exit is permitted only if the area is less than 50 m² and the number of personnel is fewer than five.

2. Personnel purification entrances must not serve as emergency evacuation exits. Because purification routes are often circuitous, it is difficult for personnel to quickly reach the outdoors in the event of smoke or fire.

3. Air showers must not be used as standard entry/exit passageways. Since the doors are typically interlocked or automated, a malfunction could severely impede evacuation; therefore, a bypass door is generally installed alongside the air shower—and is mandatory when the staff exceeds five people. During normal operations, personnel exiting the cleanroom should use the bypass door rather than the air shower.

4. To maintain internal pressure differentials, doors between cleanrooms within a clean zone typically open toward the room with higher pressure (so that the pressure seals the door shut), which conflicts with standard emergency evacuation requirements. To reconcile the needs of cleanliness during normal operations with those of emergency evacuation, doors connecting clean zones to non-clean zones or the outdoors are designated as emergency evacuation doors; they must open in the direction of evacuation—a rule that also applies to dedicated emergency exits.

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