FreeSporePrints said:

I've found also this diciture on HEPA h14 catalogues but i don't know what's it.

Can anyone help me?

is important to planning the flowhood?

Thank you.

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Quote:

mycota
Easier to C&P this than write you a whole ne explanation:

Every filter has a different "resistance" when air blows through it at a certain speed, this resistance is called the "static pressure".

Press your hand against your mouth. Now try to blow through it. Dependant on how firm you press it against your mouth, you will have some difficulties blowing air out and you will feel some resistance, this is the static pressure.

Every filter has a different static pressure at the working point. The working point is where the amount of the air flowing through the filter is sufficient to meet the requirement of the laminar flow.

The static pressure is expressed in inch of water column in the english units, a typical value would be 1", the SI unit for pressure is Pa(Pascal).

1" water column is around 250 Pa. Each filter has a data sheet (consult the manufacturer if this is not the case) where the static pressure at the working point is entered. Before the air enters the blower it is usually pre-filtered by a furnace filter around 1"(2.5cm) thick placed in front of the blower to protect it and the HEPA filter from big paricles like dust and hair. It can be assumed that the static pressure for this prefilter at the working point is around 0.2"(50 Pa)

Matching a blower to the filter
According to Stamets (Paul Stamets and J.S.Chilton: The Mushroom Cultivator p. 347 ff) the air speed of the air flowing from the filter surface should be (at least) 100 feet per minute(fpm).(around 30 meter per minute or 0.5 meter per second).

1. Find out the area of your filter by multiplying the width and the hight in feet (for instance the smallest reasonably usable filter would be 2ft x 1ft)

2ft x 1ft = 2 ft2

2. Multiply the required air speed(the one Stamets specifies) with the area of your filter

100 ft/min x 2 ft2 = 200 ft3/min

So 200 ft3/min(cfm) is the amount of air your blower must deliver at the STATIC PRESSURE of the HEPA filter + prefilter.

NOTE: 1 cfm= 1.7m3/h

So if you use the above filter with 1"(250Pa) static pressure and a furnace prefilter with a static pressure of 0.2"(50Pa) your blower must deliver 200 cfm(340m3/h) of air at a static pressure of 1.2"(300Pa).

Finding the correct blower
Every blower should have a data sheet with a characterisitc curve that shows the air output in dependance of the static pressure.

Credit to ANNO

Mycota (6T)

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