Nina,
Some of these questions are specific to your state...We have a place in New 
Jersey that will store slides for us, for as long as we need them.  The 
blocks only need to be stored for 5 years...are you plannning on being CAP 
regulated?  State to state require different specifications for fumes, fume 
hoods ect.  We I worked in a private lab in Fla. it was once an office 
building.  We had vents installed all around the room.  These vents (intake) 
are great, and work well.  You could have someone (maintenance person) make 
plasticl-like hoods which will go above the vents so that the fumes will be 
drawn to that area.  The best thing to do it get a good monitoring company 
that will come in every 6 months (mimimum) to check for formaledhyde and 
xylene (I would try to avoid using xylene at all) (clear rite 3 is a good 
substitute, and can be used in staining and the tissue processors).  If you 
monitor you can never go wrong you are not only covering the regs, you are 
protecting yourself.  
CAP has a site on the web, (I'm not sure what it is, but i'm such that others 
will know it...)
Good luck
Toni