In general, most caves have a draught, that is felt on the cheek but is too low to measure. The speed of such draughts can be measured with an anemometer, with most measuring wind speed at between 0.1 and 0.5 m/s (dependent on the measurement method).
In Cueva del Nacimiento, there is a specific section, called The Hole in the Wall that contains a significant draught. The draught here flows from deep in the cave and is forced through a small hole. It is powerful enough to blow grit directly up and out of the hole.
Picture: Anemometer reading (Alex Hannam).
This year an anemometer was taken into the cave, as a small initial test for potential future work with wind speed readings. Two readings were taken, one on the way in and another three days later, on the way out. The reading was captured with a few seconds worth of film showing the value on a TOPTES TS-301 Digital Anemometer. As it was only a few seconds of film, the variation in wind speed can be estimated.
The two readings were surprisingly different:
| Date | Approx. Speed (m/s) | Approx. speed (km/hr) | Temperature (°C) | Humidity |
| 8 September 2024 | 7.0 +/- 0.2 | 25.2 | 9.2 | 82 % |
| 10 September 2024 | 5.4 +/- 0.2 | 19.4 | 7.0 | 99.9 %* |
Table: Hole in the Wall, Cueva del Nacimiento – wind speed measurements 2024.
* The difference with the second humidity measurement may be correct. However, if the anemometer was damp, after passing through the small wet duck on the way back from Consort Hall, it could be an inaccurate reading.
At between 5m/s and 7 m/s the wind speed is significant enough to warrant placing a logging anemometer at the Hole in the Wall on a semi-permanent basis to record the speed over a year long period.
Logging the speed throughout the year may show changes in wind speed or even direction, potentially associated to water levels in the cave.