A vehicle occupant sensing system that includes at least one sensor and at least one sensor assembly. The sensor assembly has a base and an upper slide member supported for movement toward and away from the base wherein the sensor is operable to detect movement of the upper slide member toward and away from the base. The vehicle occupant sensing system also includes at least one contamination barrier member operatively attached to the upper slide member and at least partially shielding the sensor assembly to decrease contamination of the sensor assembly. The vehicle occupant sensing system may be employed in a vehicle seat to detect a condition of the vehicle seat.