A leak hole (through hole) for discharging intruded and deposited liquid is made through the wall body of the sub-passage.

Each leak hole (40) might have a diameter between 0.5 and 4.0 mm.

A leaking hole (15) and a terminal strand (16) are provided on the side wall of the hollow drive shaft.

Since the pressure difference is substantially equalized between the openings of the leak hole on the inner wall side and on the outer wall side of the sub-passage, outflow of gas from the leak hole is reduced.

Furthermore, a leak hole (42) for leaking the oil from the differential pressure chamber (8) to the outside of the body (2) is formed on the body (2).

The apparatus of the present invention includes modifying a conventional face mask respirator by providing the respirator with a pressure sensor and a leakhole of known dimension.

There are a live wire terminal, a zero line terminal, a groundwire terminal and one leaking hole on the bottom of the convex connector.

A protrusion for generating a dynamic pressure in an opening is provided in the vicinity of an opening face of the leak hole on the outer wall side of the sub-passage.

The advantage of said diagnostic module is that the diameter of the throttle openings (25-27) is less susceptible to clogging and substantially larger than the diameter of a permissible leak hole.

Measurement error of flow rate is reduced by suppressing variation in the flow rate distribution in the sub-passage when the leak hole is clogged and not clogged with a liquid drop or a liquid film.