Not sure if anyone else likes to burn fires this time of year in a fire pit in your backyard, but after some digging I found the burning code for Fairfax County.
If you need to know what the laws are you can check out all the details below:
Standard restrictions are in place for diameter, height of fire and the code distance is at least 15' from any combustible materials (ie a deck). Funny you see people all the time with fire pits sitting on their decks. :-D
Outdoor Solid Fuel Burning Devices - Fairfax County, VA