Method
Room volume, required airflow and FFU quantity from explicit ACPH and FFU airflow.
Equations
V = L · W · H
V̇ = V · N
n′ = V̇qFFU
n = ⌈n′⌉rounded up
Symbols and units
| Symbol | Quantity | Unit |
|---|---|---|
| Inputs | ||
| L | Room length | m |
| W | Room width | m |
| H | Room height (to the ceiling grid) | m |
| N | Target air changes per hour | 1/h |
| qFFU | Airflow per FFU | m³/h |
| Results | ||
| V | Room volume | m³ |
| V̇ | Required airflow | m³/h |
| n′ | Raw FFU quantity | count |
| n | Recommended FFU quantity | count |
Assumptions and limits
- ACPH and FFU airflow are explicit inputs; no defaults.
In practice
- The air-change rate follows from the cleanroom class and the client’s requirement; FFU airflow is taken at the selected speed from the maker’s data.
Worked example
The input values are the calculator's own verification test, run through the calculator. They show the working; they are not design values.
Inputs
| L | Room length | 10 m |
| W | Room width | 5 m |
| H | Room height (to the ceiling grid) | 3 m |
| N | Target air changes per hour | 6 1/h |
| qFFU | Airflow per FFU | 1,000 m³/h |
Results
| V | Room volume | 150 m³ |
| V̇ | Required airflow | 900 m³/h |
| n′ | Raw FFU quantity | 0.9 count |
| n | Recommended FFU quantity | 1 count |
A preliminary check for engineer review, not an engineering approval. The project calculation to the applicable codes, authority requirements and specification governs.