IFGC 503.6.6 on gas vent terminations
804.3.3 of the IMC deals with power venting kept 10ft from lot lines. If this applied to all vents, there would be no way to heat townhomes with combustion appliances.
As for fresh air intakes, if within 10 feet horizontally, the vent discharge must be at least 3ft above the inlet. IFGC503.8