Hi Dennis, I think I didn't make myself clear, I apologise.
What I mean is: The 280's have great isolation in comparison to any "normal" headphones. You can play drums (+100db) and listen to an iPod at lower volume than with earbuds on a bus, like at 50% volume, so I guess that counts as a lot of isolation. (it's impossible to play drums and listen to music clearly with regular earbuds or cheap closed headphones alone).
However, they don't provide the kind of isolation that earplugs or earmuffs do.
The earplugs I wear are the ones the use for Nascar racing. These:
http://www.moldex.com/hearing-protection/foam-earplugs/sparkplugs.php
They are rated as NRR33, which should be the equivalent of a 33db noise reduction.
The Senn 280's claim
"up to 32db noise reduction", and I'm sure it's true, but definitely that 32db top isn't attenuated at the same frequencies that the Moldex earplugs.
I think I'm not being very clear (sorry, it's late and I'm tired so my English is not at its best right now).
What I'm trying to say is that these cans don't isolate the way that earplugs or earmuffs do. And after 40 minutes of playing, your ears start ringing, which doesn't happen with the earplugs/earmuffs.
Ergo: Not safe to drum with them.
Cheers.