A pressure probe assembly for attachment to a venturi of a gas-fired appliance, where the venturi includes a body having an inlet end, an outlet end, and a wall defining a mixing chamber extending from the inlet end to the outlet end about an axis. A support member is detachably coupled to the mixing chamber. A first pressure probe is coupled to the support member and has a first pressure tap disposed substantially adjacent the axis. A second pressure probe is coupled to the support member and has a second pressure tap disposed substantially adjacent the mixing chamber wall. Also disclosed is a gas-fired appliance, such as a water heater, including the pressure probe assembly.