In an air pressurized system for use in delivering seeds in an agricultural planter from a main hopper to plural remote bins each associated with a respective seed discharge unit, an air/seed mixture is provided to a seed discharge unit via an air pressure dissipator which vents the air to the atmosphere in controlling the rate at which seed is delivered to the seed discharge unit. The air pressure dissipator includes an upper, angled tube having an outwardly tapered lower end adapted to receive an upper end of a perforated screen tube which extends into the seed discharge unit. As the seed discharge unit fills with seed during operation, the air pressure dissipator regulates the air flow entraining and transporting the seed by directing a portion of the air to the atmosphere when necessary to provide seed to the seed discharge unit to substantially match the seed discharge rate.