Abstract: An improved sensor support subassembly for a chemical sensor in the testing of gaseous emissions. The sensor support subassembly of the present invention comprises means for slideably engaging a sensor unit with a gas intake manifold block. The sensor unit comprises a cylindrical base which forms the inlet to the sensor. The manifold block comprises a gas intake means, a gas channel and a U-shaped slot for slideably engaging the sensor unit's cylindrical base within the manifold block such that an air-tight passage is formed between the sensor inlet and the gas channel. The sensor support subassembly also provides a sealing means for ensuring an air-tight seal between the sensor unit and the manifold block. This slidable engagement scheme allows the sensor unit to be rotated about the axis of the cylindrical base, which in turn facilitates the use of a card-edge connector for making the electronic connections between the sensor and the sensor testing system power and data lines.