Code Question

Is there a minimum distance (horizontal and vertical) that must be maintained between the gas service line and where a direct vent boiler is vented? How about spacing from window?

I am in the planning stages of replacing my oil fired boiler with a gas boiler and am leaning on going with a Muchkin or other direct venting type boiler. I am arranging on getting the gas service to my house and the most obvious choice for the spot to bring it in is also where I would want to vent the boiler. How far can the vent be piped within the house if I need to go to another wall?

Thanks.