If I recall correctly (without consulting the survey but with reference to GrahamI's surface map), Lake Level (Floor 1) and Floor 4 are the only two to have a single adit, with the remainder (most of the way up) having an adit per vein (Back/Old).
Floor 4 also has an adit in the North Vein (not to be confused with the original nomenclature which labelled the Back Vein as the North Vein), but that's an oddity to say the least.
The Floor 2 OV adit is the smoke flue, the Floor 2 BV adit is now buried under the tip, but there is/was still some airflow through it.
Then heading upwards:
Floor 3 BV adit is under the tip, somewhere above Floor 2 BV and is reached from the top of Floor 3 via a long tunnel, but again is blocked.
Floor 3 OV is somewhere above the Smoke Flue, but is lost. GrahamI's book suggests that the two Floor 3 adits were connected by a tramway along the face of the tip, in which case it's probably not impossible to locate it.
I'm not aware of anyone making it to Floor 3 OV?
The Floor 4 adit is blocked permanently and the inside end (OV) is extremely unpleasant and thankfully very difficult to get to.
Then, there are various adits above this which do not go far: there were originally BV adits on Floors 5, 6, 7, 8 & 9; and OV adits on 5, 6, 7 & 8.
We've poked into a fair few adits up in the tips, but never quite got round to working out which ones they are. This is complicated massively by the destruction caused by untopping, which has removed the inclines/levels as a means of identification.
Still, it'll provide an afternoon out sometime...
Hello again darkness, my old friend...