The determination of the airtightness of flexible hoses is described in the NEN-EN 13810.

The formula for maximum air leakage for flexible hoses is:
øL/app = f.Ps 0.65. (π.dn.L)

In which:
øL/app = maximum amount of air leakage in l/s
f = leakage factor
Ps = static pressure Pa
dn = nominal diameter in metres
L = length of component in metres (minimum length of hose according to NEN-EN 13180).