User blog comment:Godisme/Magical Barrier Particles/@comment-24066070-20131031173028/@comment-7418318-20131031175715

I don't think not breathing it in is enough. Mages absorb Ethernano from the surroundings, it's possible they could be absorbing those poisoned Ethernano particles just by being surrounded by them.

Sure those mages were wearing gas-masks, but those are part of a full-body suit that don't leave a single bit of skin uncovered.

That their entire head is hidden under the mask and the gloves and all might just be there for looks, or it might really be hermetically sealed enviromental suits.