I use six unglazed quarry tiles (each about 6"x6", from Home
Depot). I lay them on the oven's middle shelf. I've used one set
for about 3.5 years. They hold up fine. Also, we have not suffered
any ill health effects, so they're *probably* safe.
I also put three tiles in an old heavy gauge baking pan and put the
pan on the oven's bottom shelf. After putting the loaves in, I pour
a cup of hot water into the tray and quickly close the door. (WEAR
OVEN MITTS!) I prefer doing this to spraying because a. the method
generates more steam and b. I don't need to open & spray several
times (as called for in Breadbaker's Apprentice).
Andy Nguyen