HEPA / ULPA Quantity Design Guidelines

For the Semiconductor/Auto/Electronic/Mems/industries:

Filtration Classification Quantities and Percentage
of Coverage
Fed 209E English Fed 209E Metric ISO 14644-01 Recommended Percent
of HEPA/ULPA Ceiling
Class 100,000 M6.5 Class 8 4% diffused air
Class 10,000 M5.5 Class 7 10% recommended diffused air
Class 1,000 M4.5 Class 6 27% recommended laminar flow air
Class 100 M3.5 Class 5 54% laminar flow air
Class 10 M2.5 Class 4 90% laminar flow air
Class 1 M1.5 Class 3 100% laminar flow air


Ceiling Coverage Calculations

To determine the recommended ceiling coverage required with 2' x 4' HEPA’s or ULPA’s divide the square foot of the cleanroom by eight (2' x 4') then multiply the recommended percentage and that will provide you with the quantity of units needed.
Note: The recommended quantities are for reference only. They are based on optimum room layout and design to obtain certain class cleanrooms with the minimal amount spent on filtration. The arrangement and spacing of filtration are one of the most crucial characteristics of cleanroom design. Equipment layout return air grills and personnel have profound impact to the fluid dynamics of the room. Cleanroom protocol and maintenance also are key factors in ensuring constant contamination control to desired specifications.

For the Medical Device/Bio Sciences/Pharma

Existing Condition

Room Air Changes Per hour Max # of 2x4 opening 376
Length Percent Coverage 12%
Width HEPA Filters needed 46
Height CFM per HEPA 526
Filter face velocity Estimated Watts per FFU 95
Face Area of each HEPA
Energy Cost ($/kWh) 0.12
Hours of operation per year 8760

When designing the HEPA/ULPA location, you must be cognizant of the room furniture and equipment/tool layout. As this will drastically affect the fluid dynamics of the room and may create grey zones and migrating of particles into dead zones. It will also affect the flow to the low air wall returns or diminish the raised floor capability to pull air evenly throughout the cleanroom.
The arrangement and spacing of the HEPA/ULPA filters are the MOST important aspect of the cleanroom/Lab design. It can make the room fail in testing or worse yet, it will pass but have areas where your product gets contaminated unbeknownst to you until it is too late.