A system and method for administering nitrous oxide to a patient has a fluid control system that allows a user to monitor and control the supply of gases to a patient. A shutoff valve allows a user to selectively activate the fluid control system. Oxygen flow is adjusted by a flow controlling valve. A differential pressure regulator allows flow of nitrous oxide in response to sufficient oxygen flow. Flow of the nitrous oxide is further controlled by a ratio controlling valve. A display shows the flow of the gases through the fluid control system. A flush valve allows a user to flush the output with oxygen. A flow indicator light may be included. An optional output selector allows the user to direct the flow to one of various output ports. An optional safety scavenge valve prevents operation of the fluid control system when there is insufficient scavenge vacuum pressure.