An improved hot wire gas flow sensor is disclosed having a housing with a passageway in series with a passageway through which the gas flow is measured. The housing includes both a hot wire and cold wire disposed within the passageway. A current circuit maintains the temperature differential between the hot wire and cold wire preferably in the range of 30° C. to 100° C. by varying the current flow through the hot wire. Current limiting circuitry is then utilized to limit the current flow through the hot wire and thus the temperature of the hot wire in order to prevent possible combustion of the gas in the passageway. Additionally, a current augmenting circuit augments the current flow through the hot wire for a limited period of time following the electrical energization of the flow sensor in order to provide rapid heat up of the hot wire in the hot wire sensor. Improvements are also disclosed for fluidly sealing the electrical leads to both the hot wire and cold wire to prevent gas leakage from the sensor.