The Origin of Cave Draughts - Question

[Graigwen]

We find Arctic Hayes Strikes Smoke Matches excellent. They have a burn time of 20 seconds which makes them ideal for testing draughts.

Arctic Hayes Strikes Smoke Matches 33.3000B

Grey smoke matches with a burntime of 20 seconds making them ideal for testing airflow and leaks on gas appliances.

www.cityplumbing.co.uk

With a burn time of 20 seconds these sound fine for caves, but I am a bit worried by the final other use suggested...

"Grey smoke matches with a burntime of 20 seconds making them ideal for testing airflow and leaks on gas appliances."
.

 

[Chocolate fireguard]

Our dig is quite deep in the cave and has cold air rising into it from a 45 degree slope (we can't quite get into yet). Does this mean we are at the top of the chimney? I tried reading the pdf up above but my french is rusty and the document wasn't a breeze

IF the incoming air is noticeably colder than cave air, AND it only happens in winter, doesn't that mean there is another connection to the surface that is lower than the one you used (and not too far away)?
If either of those conditions is not met I have no idea.

 

[pwhole]

I was at our digging face last week, and a recently-exposed fissure in the 'floor' was pouring freezing-cold air upwards and inwards at me - clearly outdoor air as I could smell it, and it was much warmer inside then. But we're only a couple of metres higher than the entrance really, and the fissure is visibly deeper than that. And there is documented cave nearby that goes lower than where we are.