Anonymous, i certainly hope that you are not using cedar.  If you use it,
please, go to
http://www.trifl.org/medical.shtml
and in the side bar select the section on cedar and pine.  Cedar is
always dangerous.  Pine is more a matter of allergies for some, but
these can be severe and even fatal for those individuals.  Most ferrets
show no signs of having troubles from it, but some can becomes severely
ill very rapidly.  We use pine pellets ourselves wihtout problems but I
know a few people with ferrets allergic to it, including one of a vet.
[Posted in FML issue 4136]