Gas probes

1. A gas sampling probe comprising:

an elongate member having an inlet end and an outlet end; and

a sampling passage disposed within the member, the sampling passage extending from the inlet end to the outlet end,

wherein the inlet end comprises a curved outer surface treated using a passivation process to reduce surface activity and particulate adhesion, and

wherein the member comprises a helical fin.

2. The gas sampling probe of claim 1 , wherein the inlet end further comprises a seal between an outer surface of the sampling passage and an inner surface of the member.

3. The gas sampling probe of claim 1 , wherein the curved outer surface corresponds to a surface formed by revolving a smooth curve about a center axis of the sampling passage and/or member.

4. The gas sampling probe of claim 1 , wherein the curved outer surface comprises a hemispherical shape.

5. The gas sampling probe of claim 1 , wherein the outer surface comprises a surface roughness less than 0.4 μRA.

6. The gas sampling probe of claim 1 , wherein the sampling passage comprises a cross sectional area between 0.1 mm 2 to 30 mm 2 .

7. The gas sampling probe of claim 1 , wherein an inner surface of the sampling passage comprises a surface roughness of less than 0.8 μRA.

8. The gas sampling probe of claim 1 , wherein an inner surface of the sampling passage is treated by electro-polishing to reduce surface roughness.

9. The gas sampling probe of claim 1 , wherein an inner surface of the sampling passage is treated with using a passivation process to reduce surface activity.

10. The gas sampling probe of claim 1 , wherein:

the gas sampling probe is adapted for use with a conduit carrying a flowing fluid, the conduit comprising an axis parallel to the fluid flow; and

the gas sampling probe is adapted to be inclined at an angle “a” relative to the axis, where “a” is in the range 45° to 90°.

11. The gas sampling probe of claim 1 , wherein the member comprises a tube.

12. A probe main body for insertion into a pipe transporting fluid, the probe main body comprising:

an elongate upper tubular portion;

an elongate lower tubular portion which is integral with and having a diameter smaller than the upper tubular portion;

a sampling bore which extends between the upper and lower tubular portions; and

a plurality of helical fins integrally formed on the lower tubular portion and which wind along and around an outer surface of the lower tubular portion and which overlap each other,

wherein a radial extension of the lower tubular portion plus helical fins substantially corresponds to an external radius of the upper tubular portion.

13. The probe main body of claim 12 , wherein each of the plurality of helical fins originates on the outer surface of the lower tubular portion at a separate location.

14. A probe main body for insertion into a pipe transporting fluid, the probe main body comprising:

an elongate upper tubular portion;

an elongate lower tubular portion which is integral with the upper tubular portion;

a sampling bore which extends between the upper and lower tubular portions; and

a plurality of helical fins integrally formed on the lower tubular portion and which wind along and around an outer surface of the lower tubular portion and which overlap each other,

wherein each of the plurality of helical fins originates on the outer surface of the lower tubular portion at a separate location.