1. A particle number counting apparatus comprising:
a saturator part including a flow path in which a working liquid is diffused in a vaporized state so as to render sample particles contained in a measurement targeted gas to flow in the flow path;
a condenser part for introducing the sample particles and vaporized working liquid from the flow path and condensing the working liquid with the sample particles as cores so as to produce droplets of the working liquid; and
a counter part for counting the droplets of the working liquid,
wherein the saturator part includes a porous member in which the flow path is passed through to form an inlet at a lower side and an outlet at an upper side thereof so that the working liquid is supplied to a predetermined section of the porous member so as to be impregnated into the entire part of the porous member, and a housing having an accommodating space for accommodating the porous member, wherein
a gap is formed between at least an upper side of an outer peripheral surface of the porous member above the predetermined section of the porous member to be supplied with the working liquid and an inner peripheral surface of the accommodating space of the housing wherein the gap has a width not to cause a capillary phenomenon.
2. The particle number counting apparatus as claimed in claim 1, wherein the gap is continuously and circumferentially formed.
3. The particle number counting apparatus as claimed in claim 1 or 2 comprising a connection pipe connecting a working liquid introduction port for introducing the working liquid and a measurement targeted gas introduction port for introducing the measurement targeted gas so as to equalize a pressure at each of the ports.
4. The particle number counting apparatus according to any one of claims 1 to 3, wherein the porous member has a non-porous member arranged inside thereof.

5. A saturator part as claimed in claim 1 adapted to a particle number counting apparatus which comprises: the saturator part including a flow path in which a working liquid is diffused in a vaporized state so as to render sample particles contained in a measurement targeted gas to flow in the flow path; a condenser part for introducing the sample particles and vaporized working liquid from the flow path and condensing the working liquid with the sample particles as cores so as to produce droplets of the working liquid! and a counter part for counting the droplets of the working liquid, the saturator part including:
a porous member in which the flow path is passed through to form an inlet at a lower side and an outlet at an upper side thereof so that the working liquid is supplied to a predetermined section of the porous member so as to be impregnated into the entire part of the porous member!
, wherein
a gap is formed between at least an upper side of an outer peripheral surface of the porous member above the predetermined section of the porous member to be supplied with the working liquid and an inner peripheral surface of the accommodating space of the housing, wherein the gap hgas a width not to cause a capillary phenomenon.