Mine's in my closet, so there's not an issue with moisture.
If you do, make sure you put in a heater bar or better yet, a dehumidifier (not dessicant packs, they get expensive)
Like this: Amazon.com - Eva-dry Renewable E-333 Wireless Mini Dehumidifer
Whatever you do, make sure you bolt it down to the slab. Especially if it's in the garage and you're everytime you open the garage door, you're advertising to your neighbors "hey, look here... I've got some stuff worth stealing inside this here safe".