I've been reloading for more than a decade, without incident, about 4 or 5 feet from the furnace. I attribute that to a little caution, as stated elsewhere in this forum. I always sweep up after a reloading session - I've heard vacuums can cause powder to ignite and burn (never heard of anyone who has has this happen) but I'd rather error on the side of caution. Powder & primers are both on my bench - extra powder is in a wooden foot locker (I made the foot locker out of 2x4's lined w/plywood inside) extra primers are on the floor (elevated a few inches to protect them from any possible water) under a nearby bench. A friend of mine stored 30k primers on the floor that had never seen water - Murphy strikes again - a leak soaked ALL the primer boxes. He carefully opened all and allowed them to dry completely. Currently he is using them and has not had a problem!
In a fire, powder & even loaded ammo has NO possibility of exploding. The powder may contribute to the fire by burning, the ammo will not fire - needs to be a firearm for that to happen. The heat of the fire will cause the powder - in the loaded ammo - to slowly expand pushing the bullet out of the case or splitting the case.
So, your answere is go ahead and start reloading in the basement.
I'm not a neat freak, but keep my bench resonably clean (not always organized).