please explain me..

[garde.anand]

i just wonder about why LAF velocity is 90 FPM?? and in which room requires LAF?

please explain me...

[nike123]

i just wonder about why LAF velocity is 90 FPM?? and in which room requires LAF?

please explain me...

What means "LAF"?

[Brian_UK]

We explain to you when you do not use initials; LAF is what??

[raghav]

LAF means laminar air flow. In laminar air flow the velocity is 90 FPM. But i cant understand the logic behind it.if anybody knows the answer please explain me? again in which class and in what particular room requires LAF ???
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[TRASH101]

I assume you are not refering to laminar extract.


LAF is used in various applications such as clean rooms (class 100 or better usually) with specific particle control such as micro biological, some nanotech and so forth.

The advantages of LAF over turbulant is that any particle pick up form shedding/ release is carried within the laminar stream to point of exit with little (ideally no) cross contamination to anywhere else except the laminar path.

disadvantages are (apart from vent cost) is specifc design lab fixtures and fittings (everything must be aerodynamically designed to eliminate eddy currents as best it can) and the placement of them so as the laminar paths can be optimal.

[TRASH101]

Where did you get your 90 fpm value?

The velocity you use depends on various factors such as filtration, anticipated particle sizes.

Length of laminar path.

Vertical path or horizontal path.

Occupancy comfort levels (type of barrier clothing if any)

[raghav]

thanks TRASH101. U have given much more information for me.. do u have any work experience in cleanroom. if u have & if u want to share any knowlege to me. u r always welcome...
once again thanks for giving me such valuable information.....

[zubair.adnan]

Hi,
I have found the following information which answers your question. I have directly copied the material from the source.
Source: http://www.gmpua.com/CleanRoom/Design/Clean%20Room.pdf

Why 90 fpm?

The definition of laminar flow, 90 fpm plus or minus 20% does not exist officially. As a common industry practice, manufacturers and designers design the system at this velocity. The primary purpose is to provide adequate air at a velocity to keep airflow straight in uni-directional that can effectively dilute and carry away particles or contaminants generated within the room.

[dougheret0]

Laminar flow actually refers only to fluid flow (gas or liquid) in a duct. It is defined by a low Reynolds number, and is not actually the correct term for uniform cleanroom flow. To quote the ASHRAE Handbook, Applications: “Unidirectional air flow, though not exactly laminar, is characterized as air flowing in a single pass in a single direction through a cleanroom with generally parallel streamlines.” To further quote:
“In a horizontal-flow cleanroom, the supply wall consists entirely of HEPA or ULPA filters supplying air at approximately 90 fpm or less (my emphasis) across the entire section of the room. Air then exits through the return wall at the opposite end of the room.”