Abstract: Sheath systems 20, 40 are attached to the chemical emitting ends of permeation devices or permeation tubes 10, 30 to retard the release of stored chemicals before the intended use of the improved permeation devices. Sheath systems may be made of polyolefin material, Fluorinated ethylene propylene (FEP) resin or other material in a heat shrink configuration wherein heat is applied to contract, shrink wrap or otherwise secure the sheath to a permeation tube. At the time of intended use, the sheath assembly may be removed without damage to the permeation device.

Abstract: A system used for permeating or emitting a gas or a chemical at a constant, predictable and controllable rate uses an amorphous fluoropolymer material as a gateway. The system may comprise a tube assembly which holds a gas or liquid. The gas or liquid permeates though the fluoropolymer material to be released in precise quantity, resulting in known concentrations of the gas, when mixed with a flowing or carrier gas such as air or nitrogen.

Abstract: A system used for permeating or emitting a gas or a chemical at a constant, predictable and controllable rate uses an amorphous fluoropolymer material as a gateway. The system may comprise a tube assembly which holds a gas or liquid. The gas or liquid permeates though the fluoropolymer material to be released in precise quantity, resulting in known concentrations of the gas, when mixed with a flowing or carrier gas such as air or nitrogen.

Abstract: An electrochemical gas sensor having a flexible membrane mounted at the sensing end of a housing, to dissipate increased electrolyte pressure, a small sensing electrode cooperating with a relatively thick porous sheet of polytetrafluoroethylene (PTFE) supported by the flexible membrane, and the housing also containing an electrolyte and a counter electrode, with suitable circuitry connected to the electrodes for quantifying the current generated by the sensor.

Abstract: An electrochemical gas sensor having a relatively small sensing electrode (12) formed from powdered metal pressed onto a relatively thick porous sheet (24) of polytetrafluoroethylene (PTFE), through which gas is diffused. The electrode (12) is located at one end of a housing (10) containing an electrolyte (22) and a counter electrode (14). The sensing electrode structure provides relative insensitivity to temperature changes, rapid response to pressure charges, and a desirably low operating current.

Abstract: A device for emitting a gas at a constant rate into a moving fluid medium to produce an accurately known concentration of the gas in the medium. The gas is held in a cylinder (10) in which there are two chambers (14 and 16), one for holding the substance in liquefied form and the other for holding it solely in gaseous form. The substance permeates through a permeable material (20) between the two chambers and then through another quantity of permeable material (12) positioned at an exit from the second chamber (16). The device combines low temperature sensitivity associated with gaseous phase devices, and high permeation rates and lone useful lives associated with liquid phase devices. It is also safer than prior devices of the same general type.

Abstract: Method for the electrochemical detection of a gas and apparatus including a gas-contacting electrode, biased to a predetermined potential, a counter electrode and electrolyte between the electrodes. The electrochemical reaction between the sensed gas and the sensing electrode produces an electric current in a sensing circuit between the sensing electrode and the counter electrode. The sensitivity and stability of the device are maintained by including a conductive member in spaced relationship to the sensing electrode. In accordance with the method, the conductive member is biased to the same potential as the sensing electrode and is selected to have the same response to factors affecting the zero current as the sensing electrode. The conductive member is electrically connected to the sensing electrode so that their zero current outputs are continuously balanced.

Abstract: A gas sample flowing through the lower chamber of a diffusion cell diffuses through a membrane into the upper chamber at a rate above a determined minimum. As the sample diffuses through the membrane, substantially all of the water and any particulates are removed from the gas. A clean carrier gas flows through the upper chamber at a constant rate to dilute the diffused gas and convey it to gas analyzers. Upon acquisition, a gas sample is maintained at a temperature above its dew point until it passes from the lower chamber and the membrane is maintained at a substantially constant temperature.