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By vampirita
Posts:  15
Joined:  Mon Nov 15, 2010 12:13 am
Hello all.
I am trying to build my own laminar flow hood, but i have a little confusion regarding the pressure of the blower.
Actually my hepa filter is 35x35 cm.

airflow = width * height * air speed =
= 0,305 m * 0,305 m * 0,5 m/s =
= 0,0465125 m³/s * 3600= 167.445

Until here it is ok. So i will need (167.44 m³/h) blower, but the thing is how do i choose/ calculate the right Pa i will need?
how much pressure is necessary to transport 167,44 m³/h air through the HEPA Filter?

I have seen many filters with different Pa. I heared that 150 Pa is the right pressure on a 305*0.61 hepa filter size.

Thanks for the help...
By Milhaus
Posts:  109
Joined:  Wed Mar 10, 2010 4:07 pm
The pressure depend upon your HEPA filter ( filter depth and material ), look at the HEPA datasheet.It is mostly around 150 Pa.
BTW you need more than 167m3/h, at least 2 times more ( due prefilter and HEPA filter clog after time )
By vampirita
Posts:  15
Joined:  Mon Nov 15, 2010 12:13 am
Thank you milhau for answering me.
But how exactly do you guys knows whats is the right blower, cause the specifications of my filter says they have tested it under the following conditions:
150m m3/h with a 150 pa and it had 99.9 efficacy.
Actualy my blower is 190 m3/h with 150 pa but it looks like very poor in ventilation.
So how do you know you really have 0.5 m/s ventilation or the right one? or how exactly do you measure the right filter´s effectiveness previous to install the blower?

Thanks a lot...
By Milhaus
Posts:  109
Joined:  Wed Mar 10, 2010 4:07 pm
1. You need pressure/air flow graph of the blower. Information from manufacturer that the blower does have 190 m3/h and 150 pa are misleading.
2. To maintain 0.5m/s flow you need power regulator before vent. And you need to measure the flow with flow meter.
By vampirita
Posts:  15
Joined:  Mon Nov 15, 2010 12:13 am
Thaks milhaus.
Actually i got another blower with 400m3 with 210 pa and untill now it looks greate. i Know is more stronger than the one i really need.
Actually the only way i have to measure the air flow is by puttin the traditional candle and check the 40- 90 flame degrees.
I hope it works and i already did my first test with some jaars.
The thinks is that my filter is 305ml*305 ml and it was very dificult to get a blower that match it size.
Therefore the space for the blower of my laminar is a little bigger than the filter´s size.

I will see now,,,
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