There's some good posts about setting up a studio in a basement on
http://www.artglassanswers.com/forum/index.php
It's worth getting a membership so that you can see the photos and pictures.
Working in a basement where you have a water heater, furnace or other gas-fueld appliance can be problematic if you don't take special steps. You are very likely sucking spent combustion fumes from your furnace or water heater right towards you by virtue of your lampworking ventilation fan. That could easily explain your symptoms - you may be getting a higher exposure from these appliances than from your torch. Torching in a basement takes some careful planning to avoid just this kind of problem. I highly encourage you to go to Art Glass Answers and read the various discussions on working in a basement.
Linda