To determine the permissible air leakage of valve registers, an equivalent length of 1 metre is specified for the length of these fittings, if the actual length is less than or equal to 1 metre.
For practical reasons Luka has agreed with suppliers and manufacturers to use this equivalent length for all rectangular fittings. This to the extent that the technical execution allows it and the actual length is less than 1 metre.

The formula for maximum air leakage for rectangular fittings is:
øL/app = f.Ps 0.65.(2H + 2W).L

In which:
øL/app = maximum amount of air leakage in l/s
f = leakage factor
Ps = static pressure Pa
W = width of the component in metres
H = height of the component in metres
L = length of the component in metres, L = 1 if the length of the fitting is less than 1 metre or the actual length if the length is more than 1 metre.