Air Permeability – Converting CFM to cc

MHW Kor preshell is Pertex Quatum Air, and they are being closed about all over. In both pullover and full zip hooded versions

FWIW I have the MH Kor preshell shirt and it is a good aerobic layer for cycling and walking in cool air temperature.  It feels quite good against the skin but I always have a base under it.

My crude darth vader test (breathing through the garment) shows a reasonable air permeability.

I’m trying to convert air permeability expressed in mm per second to CFM. It was measured using ISO 9237-1995 standard with a 20 cm2 testing area and a pressure of 100 Pa.

Should I divide the value (mm/s) by 4 to convert it to CFM?

I think dividing by 4 is correct. I’m going by this air permeability conversion guide by IDFL.

CFM is (ft3 / min) / ft2 @ 125Pa

(air permeability in (ft3 / min) / ft2) x 5.08 = (air permeability in (litres / m2) / second)

1 mm / s = 1 (litres / m2) / second

(air permeability @ 125Pa) x 0.8 = (air permeability @ 100Pa)

This gives –

(air permeability in (ft3 / min) / ft2 @ 125Pa) = (air permeability in mm / s @ 100Pa) / 4.06