Abstract: An apparatus and method for inserting a new service pipe into an existing service pipe without the necessity of excavation or separately shutting off the supply of gas upstream of the effected pipe section comprises of a nosecone allowing a flow of sealer to travel back through an annular space between the new pipe and the old pipe, providing a gas tight permanent seal.

Abstract: A thermal gas sensing apparatus for a gas detector is provided with a gas compartment containing a gas, a gas sensor exposed to the gas in the gas compartment, and a temperature sensor exposed to the gas in the gas compartment. The gas sensing apparatus includes a circuit for generating a gas signal having a magnitude which relates to the heat capacity of the gas and a circuit for generating a temperature signal having a magnitude which relates to the temperature of the gas. The apparatus includes a circuit for supplying a variable magnitude of electrical current through the gas sensor to cause the resistance of the gas sensor to remain substantially constant. The apparatus also includes a difference amplifier for generating a gas concentration signal based upon the temperature signal and the gas signal.