ISO 80601-2-69 figure 21.101 standard resistance

201.9.6.2.1.101 Additional requirements for audible acoustic energy
a) The A-weighted sound pressure level emitted by the oxygen concentrator, when tested in accordance with the method in this subclause, shall be disclosed in the instructions for use:
1) for an oxygen concentrator with a continuous flow mode,
i) at a flowrate setting of 3 l/min, or
ii) the maximum flowrate setting if this is less than 3 l/min,
iii) as well as for the maximum flowrate setting if this setting is greater than or equal to 4 l/min;
and
2) for an oxygen concentrator with integrated oxygen conserving equipment function, at the maximum demand flow rate setting of normal use.
b) The instructions for use shall disclose:
1) the sound power level; and
2) the tested flowrates.

Check conformance with the following test:
c) For an oxygen concentrator with a continuous flow mode, place the oxygen concentrator on a sound-reflecting plane and attach 10 m ± 1 m of oxygen tubing.
d) Attach the standard resistance (as indicated in Figure 201.101) to the patient end of the oxygen tubing.
Set the oxygen concentrator to a flowrate of approximately 3 l/min or the maximum flowrate setting if this is less than 3 l/min.

Key
D is the internal diameter: (4 ± 0,1) mm
L is the length: (40 ± 1) mm
A is the angle (45 ± 1) °
Break all edges with 0,15 mm to 0,20 mm radius or 45° chamfer. Drawing is not to scale.