How many FFUs are needed for an ISO 5 clean room? How to determine specifications and quantity
Direct answer: ISO 5 cannot be directly converted into a fixed number of FFU units. It should first be clear whether ISO 5 requires covering the entire room or a local process area, and then determine the target air supply and airflow organization in each area; select FFU that can achieve the target air volume under the specified filter and project resistance, check the quantity according to the air volume and ceiling arrangement, and finally confirm it through on-site testing.
ISO 14644-1 classifies clean rooms and clean areas based on the concentration of suspended particles in the air. ISO 5 defines the cleanliness results that need to be achieved and does not specify how many FFUs must be installed in a room. Two projects with the same area may have different FFU layouts due to different equipment locations, dust generation conditions, and return air paths.
First decision: Does ISO 5 cover the entire room, or a localized area?
The entire room requires ISO 5: It is necessary to plan the overall airflow path of FFU and return air based on the air supply area, equipment and personnel distribution of the whole room, and check whether the air supply coverage is continuous.
ISO 5 requirements for local process areas: the key areas should be delineated first, and then the airflow relationship between them and surrounding areas should be clarified. The number of FFU is mainly determined based on the air supply demand and layout of the area and cannot be calculated directly based on the entire room area.
The project should also indicate the operating status corresponding to the cleanliness acceptance. This condition affects supply air design and field verification protocols.
The second decision: What specifications should be used for a single unit?
Filter by ceiling module, available height, beam position, lighting fixtures and maintenance spaceFFU fan filter unit size, then compare the assembly specificationsAfter HEPA or ULPA filter , under the design gear and resistance conditionsthe effective air volume, static pressure and wind speed uniformity corresponding to the target air volume 。
The maximum air volume cannot be directly used as the design air volume. If the filter grade, box structure or operating gear changes, the effective air volume of a single FFU should also be rechecked.
The third decision: Are there enough stations and are they in the right locations?
Each area can first divide the required air supply volume by the effective air volume of a single FFU under project conditions to obtain the initial air volume number, and round up. Then check the air supply coverage, equipment occlusion, return air path and maintenance space of key process locations in the ceiling diagram.
The initial calculation of the air volume is qualified, but when a weak airflow area forms locally, the FFU specifications or arrangement should be adjusted; if the arrangement is dense enough, the actual total air volume and operating power consumption still need to be checked. Quantity and location should work together to serve the ISO 5 objectives.
The final quantity is determined by testing
During the prototype stage, the filter configuration, air volume and static pressure at the design level, sealing and installation conditions should be confirmed. After on-site installation, airflow distribution and particle concentration are checked according to technical protocols.ISO 14644-3 provides a methodological framework for performance testing of clean rooms under different airflow types and operating conditions. If the local air flow or cleanliness does not meet the requirements, the air supply and return organization, filters and control settings should be checked first, and then the FFU configuration should be corrected.
Aili Industrial can match the FFU complete machine specifications based on the ISO 5 area range, floor plan and ceiling diagram, target air volume, filtration requirements and control zones. For batch projects, it is recommended to confirm the prototype first, and then write the single unit working conditions, layout quantity and on-site acceptance method into the technical agreement. Specific specifications and number of units are subject to project test results.
