Disclosed are vapor delivery systems comprise a housing body defining an interior volume therein, a plurality of flow resistors for receiving a carrier gas, to generate gas distribution lines in the interior volume, at least two surfaces having the solid or liquid precursor applied thereto to allow passage of the carrier gas thereover along the gas distribution lines to mix with a solid or liquid precursor vapor, a gas-collecting device downstream of the gas distribution lines to deliver a mixture of the carrier gas and the solid or liquid precursor vapor out of the system, and a flow controller fluidically connected to a carrier gas source to control a feed flow rate of the carrier gas feeding into the interior volume. A gas distribution flow rate along each gas distribution line is controlled by the feed flow rate of the carrier gas feeding into the interior volume.