If you try to remove a logical volume you’ll get error like this:
Logical volume VolGroup00/LogVol01 contains a filesystem in use.
The solutions is to check is there open files, most likely no:
lsof | grep LogVol01
And after that identify processes using files on this volume
fuser -kuc /dev/VolGroup00/LogVol01
And hire probably you’ll get some results. All you need is to kill -9 this process and after that you can remove the virtual volume/snapshot