Gas detecting and measuring device

Abstract

A device for the detection of and quantitative measurement of a gas in a given environment, such as alcohol in the breath or carbon monoxide in the atmosphere, is described. The device comprises intake and flow control means for the gas sample, and an electrochemical cell having an anode which provides a site for electrochemical reaction of the gas being detected, a cathode, a reference electrode, and an electrolyte in contact with the anode, cathode, and reference electrode. The anode, to ensure that the current production is a result of the gas being detected and not other gases, including oxygen, is maintained at a fixed potential in relation to the potential of the reference electrode. The device provides an accurate and inexpensive means of detecting and quantitatively measuring a gas contained in a given environment, i.e., alcohol in the breath of the subject being tested or carbon monoxide in the atmosphere.

It is claimed: 
     
       1. A gas .Iadd.device for continuously, quantitatively .Iaddend.detecting and measuring .[.unit.]. .Iadd.a noxious gas in the presence of air .Iaddend. comprising in combination intake means, an electrochemical cell, means for drawing a gas through said intake means and into said electrochemical cell at a controlled flow rate, .[.and read-out means for reading the quantity of said detected gas,.]. said electrochemical cell comprising .Iadd.a housing, .Iaddend.an anode .Iadd.comprising catalyst bonded to a hydrophobic fluorocarbon membrane to provide a diffusion electrode.Iaddend., a cathode, a reference electrode at which substantially no current flows, .Iadd.all positioned within said housing, .Iaddend.and an aqueous electrolyte in an electrolyte chamber, .[.said electrolyte being in contact with.]. .Iadd.each of .Iaddend.said anode, cathode, and reference .[.electrode,.]. .Iadd.electrodes having a catalyst surface containing said electrolyte and said reference electrode contacting air, .Iaddend.means for exposing said anode to a gas to be detected .Iadd.in the presence of air.Iaddend., .Iadd.potentiostat .Iaddend.means .[.for.]. maintaining said anode at a fixed potential relative to the reference electrode of from about 0.7 to 1.5 volts with respect to a reversible hydrogen electrode potential in said electrolyte of said cell, within which range oxygen reduction or oxidation of water to oxygen does not occur, .[.said anode comprising a catalyst bonded to a hydrophobic fluorocarbon to provide a diffusion electrode and.]. said catalyst .Iadd.of said anode catalyst surface .Iaddend.catalyzing an electrochemical reaction with a gas selected from the group consisting of CO, hydrocarbons, alcohols, NO, NO 2  and SO 2  at said fixed potential.Iadd., said anode being arranged in said cell so that one surface of said anode contacts said gas exposing means and the opposite surface contacts said electrolyte whereby the noxious gas to be detected migrates from the surface contacting said exposing means to the internal surface of said anode to interface with the electrolyte for electrochemical reaction in the presence of said catalyst, means for continuously measuring said current flowing between said anode and cathode of said cell, said measured current being a measure of the concentration of the gas being detected, and read-out means for continuously reading said concentration of gas being detected.Iaddend.. 
     
     
       2. The unit of claim 1 adapted for detecting and measuring carbon monoxide and including scrubber means between said intake means and electrochemical cell for selectively collecting absorbables while permitting the gas being detected to pass through. 
     
     
       3. The unit of claim 2 wherein the scrubber means contains activated carbon. 
     
     
       4. The unit of claim 2 wherein the scrubber means contains charcoal. 
     
     
       5. The unit of claim 2 wherein the intake means is in communication with a sump bottle constructed and arranged with said intake means whereby gas to be detected and measured passes through said sump bottle prior to entering the electrochemical cell. 
     
     
       6. The unit of claim 1 wherein said means for drawing gas through said intake means and into said electrochemical cell at a controlled flow rate includes pump means and flow control means. 
     
     
       7. The unit of claim 6 wherein the flow control means is a restricted orifice. 
     
     
       8. The unit of claim 6 wherein said pump means and flow control means are constructed and arranged behind said electrochemical cell. 
     
     
       9. The unit of claim 1 adapted for detecting and measuring alcohol and including a selectively permeable membrane which will selectively pass alcohol while inhibiting the flow of carbon monoxide and hydrocarbons. 
     
     
       10. The unit of claim 9 wherein the intake means includes a multi-position valve and said valve is in controllable communication with a sample collector and the atmosphere. 
     
     
       11. The unit of claim 10 wherein the multi-position valve is further in communication with a verification sample collector. 
     
     
       12. The unit of claim 11 wherein the multi-position valve is in further communication with a calibrating sample. 
     
     
       13. The unit of claim 10 wherein the sample collector is an endless tube. 
     
     
       14. The unit of claim 1 wherein the electrochemical cell includes a composite electrode structure comprising a non-conductive base and on said non-conductive base said cathode and said reference electrode electrically separated from said cathode. 
     
     
       15. The unit of claim 14 wherein said electrochemical cell has a reservoir in communication with the electrolyte chamber. 
     
     
       16. The unit of claim 1 wherein the hydrophobic fluorocarbon is polytetrafluoroethylene.