Chemical agent leak detector and a method of using the same

#This invention relates to a chemical agent leak detector which adsorbs the vapor of the leaking chemical munition and upon so doing undergoes a change in its electrical resistance according to a known correlation.

#A need exists to monitor chemical agent munitions to determine if these munitions are leaking and thus represent a potentially dangerous situation. Presently the identification of defective munitions requires an operator to open an access to the munition and to place a sampling device within the munition cavity. The sampling devices presently being used are glass tubes containing reactive chemicals which produce a colorimetric change in the presence of chemical agent vapors. The operator must draw a vapor sample from within the munition, either manually with a hand pump or with an external vacuum pump, into the detector tube. After the sample is removed, the operator visually checks for any color change and recaps the access plug.

#The use of such detector tubes is unsatisfactory for many reasons. First, it requires the operator to generate a access to the munition cavity each time the munition is analyzed which is an inconvenience and a hazard in its own right. Second, this exposes the operator to potential chemical contamination. Third, since the detection tubes utilize chemical reagents which in turn have a limited life span, such detector tubes must be periodically replaced. Fourth, a cost is incurred due to the need to maintain a functional inventory of such tubes. Fifth, this type of analysis is manpower intensive.

#A reference to the accompanying drawings which are meant to be illustrative but not limiting will aid in a further understanding of the present invention:

#FIG. 1(a) shows a cross-sectional view of a sensor according to this invention;

#FIG. 1(b) shows an end view of the sensor shown in FIGS. 1A; and

#The chemical agent leak detector of the present invention comprises the sensor shown in FIGS. 1(a) and 1(b). The sensor is inserted into the munition. In fact, a sensor is inserted into each munition which is to be monitored.

#The detection of leaking chemical agents at the sensor is based on the adsorption of vapors onto a device known as an ADSISTOR (ADsorption Sensitive resISTOR). Typically, though not necessarily an ADSISTOR consists of carbon. Upon such adsorption these devices change resistance in a manner related to the concentration of the gas vapor (i.e., its partial vapor pressure) and the interaction characteristics peculiar to that ADSISTOR and that vapor which are involved. Known empirical data indicate that the percentage change in resistance is related to the vapor pressure of the leaking chemical munition.

#In FIG. 1(a), the actual area for this adsorption is identified by item A. The metallic sleeves or bands (e.g., copper, silver or aluminum) indicated as item B provide electrical contact to this surface and also provide a physical means to attach electrical leads. The resistance change is measured across these leads.