GB2184244A - Device for detecting a component of an ambient gas - Google Patents
Device for detecting a component of an ambient gas Download PDFInfo
- Publication number
- GB2184244A GB2184244A GB08629014A GB8629014A GB2184244A GB 2184244 A GB2184244 A GB 2184244A GB 08629014 A GB08629014 A GB 08629014A GB 8629014 A GB8629014 A GB 8629014A GB 2184244 A GB2184244 A GB 2184244A
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- United Kingdom
- Prior art keywords
- component
- sensor
- conversion means
- electrochemical
- product
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000007789 gas Substances 0.000 claims abstract description 22
- 230000000694 effects Effects 0.000 claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims abstract description 18
- 230000003647 oxidation Effects 0.000 claims abstract description 6
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 6
- 239000004065 semiconductor Substances 0.000 claims abstract description 5
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract 3
- 150000004706 metal oxides Chemical class 0.000 claims abstract 3
- 239000003054 catalyst Substances 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 4
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical group O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 4
- 229910001887 tin oxide Inorganic materials 0.000 claims description 4
- 229910000510 noble metal Inorganic materials 0.000 abstract description 10
- 230000003197 catalytic effect Effects 0.000 abstract description 6
- 150000002894 organic compounds Chemical class 0.000 abstract 1
- 239000003344 environmental pollutant Substances 0.000 description 34
- 231100000719 pollutant Toxicity 0.000 description 34
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 33
- 239000000047 product Substances 0.000 description 22
- 238000010438 heat treatment Methods 0.000 description 15
- 229940076134 benzene Drugs 0.000 description 11
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 10
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 9
- 239000000126 substance Substances 0.000 description 6
- CYTYCFOTNPOANT-UHFFFAOYSA-N Perchloroethylene Chemical group ClC(Cl)=C(Cl)Cl CYTYCFOTNPOANT-UHFFFAOYSA-N 0.000 description 5
- 229950011008 tetrachloroethylene Drugs 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- KCXMKQUNVWSEMD-UHFFFAOYSA-N benzyl chloride Chemical compound ClCC1=CC=CC=C1 KCXMKQUNVWSEMD-UHFFFAOYSA-N 0.000 description 4
- 229940073608 benzyl chloride Drugs 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 229910052737 gold Inorganic materials 0.000 description 4
- 239000010931 gold Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000005465 channeling Effects 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 229910052741 iridium Inorganic materials 0.000 description 3
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 2
- -1 Pcl Substances 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 235000013175 Crataegus laevigata Nutrition 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 230000007059 acute toxicity Effects 0.000 description 1
- 231100000403 acute toxicity Toxicity 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 239000007857 degradation product Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 239000003440 toxic substance Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0011—Sample conditioning
- G01N33/0013—Sample conditioning by a chemical reaction
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0031—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array
- G01N33/0032—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array using two or more different physical functioning modes
Abstract
A device for detecting a component of an ambient gas comprises conversion means (62,64) for chemically changing said component to a derivative product having a characteristic electrochemical activity, said conversion means having a means (64) for generating a signal when said component is present in a concentration above about 0.1 - 1.0%, but essentially unresponsive at concentrations below about 0.1%, and sensing means (74) responsive to the electrochemical activity of said product for concentrations of said component below about 0.1% for providing a signal indicative of the product and thereby the component. The conversion means may comprise a hot wire sensor having an oxidation catalytic surface of a noble metal and temperature controlled by controller (65) or it may be a metal oxide semiconductor sensor. Sensor means (74) may be an electrochemical sensor responsive to oxidised gases of organic compounds. If the conversion means (62,64) senses and indicates at (66) the presence of the component at concentrations above 0.1 - 1% then valve (70) directs the flow of derivative product away from sensor (74). When there is no signal from the conversion means the gas flow is to sensor (74). <IMAGE>
Description
1 GB 2 184 244 A 1
SPECIFICATION
Device for detecting a component of an ambient gas This invention relates to devices for detecting poll utants and more particularly to devices capable of detecting polutants at relatively low concentrations in ambient gases. Electrochemical sensing devices, especially amperometric sensors such as those dis- closed in U.S. Patent Nos. 3,776,832,4,201,634 and 4,326,927 offerthe advantages of portability, realtime readout, relatively low cost, and fairsensitivity and selectivityto a few specific pollutants such as CO, H2S, NO, N02, S02, hydrazine, COC12, HM, or C12.
However, these devices are not applicable, at preseritto the detection of many species that are not electrochemically active.
In detecting pollutants including toxic substances, sensing devices have usually been limited with re- spectto concentrations of the pollutants particularly when the pollutants are essentially not electrochemically active or have an activity difficuitto detect. Below certain values of concentration, e.g., 100 ppm (parts per million) of benzyl chloride, tetra- chloroethylene orthe like, presently available portable devices are essentially unresponsiveto the pollutant. Since some pollutants may be extremely toxic, it is importaritto develop devices fordetecting various pollutants at low concentrations.
Accordingly, one object of this invention is a device for detecting pollutants at low concentrations in gases. Another object is an electrochemical device for detecting pollutants in ambient gases where the pollutants are essentially electrochemical ly inactive or have an activity difficuitto detect. An additional object is a device which may be utilized as a portable instrumentto survey an area or as a site monitorfora wide variety of gases. Afurther object is a device which is also capable of detecting pollutants at higher concentrations, atwhich level they may present an acute toxicity orflammability hazard.
Briefly, the invention relates to a device for detecting a pollutant in an ambientgas and comprises (1) electrical conversion means having a catalytic sur- face to chemically convertthe pollutant (e.g., a hydrocarbon) to a derivative product (e.g., carbon monoxide) having a characteristic electrochemical activity, and (2) electrochemical sensing means responsive to that electrochemical activity and provid- ing a signal indicative of the derivative product and therebythe original pollutant. In one embodiment, the conversion means includes a sensor responsive to higher concentrations of an electrochemically inactive pollutant, but essentially unresponsiveto lower concentrations, and an electrochemical sensor responsive to the derivative product, but essentially unresponsiveto the pollutant at low concentrations. The conversion means may comprise a heated filament made of orcoated with a noble metal catalyst, such as Pt, Pd, 1r, Rh, Au, Ag, or an alloy orcompco,;nd of one of such metals.
Figure 1 is an exploded view of one embodiment of the invention.
Figure2 is a cross-sectional view of yet another w,5 eryjbodirneritof the invention.
Figure 3 is a flow diagram of yet another embodiment of the invention.
Figure 4shows representative response curves for benzene from devices constructed according to the invention.
The device of the invention is suitable for use in detecting at least one of a variety of pollutants or otherwise hazardous gases or vapors in ambient gas. These pollutants commonly include various or- ganic compositions such as benzene, benzyl chloride, toluene, methane, tetrachloroethylene, tetrahydrofuran, cyclohexane and the like. It is particularly useful for detecting the presence of a pollutant such as benzyl chloride or benzene at low con- centrations in the order of about 1 -100 ppm where some sensing devices are inoperative. In addition, the device may be constructed of components permitting its use as a portable instrument capable of on-site detection of a pollutant and in some instances fixed site analysis of the general concentration of the pollutant.
The device includes in combination, electrical heating means having a noble metal exposed surface forchemically changing the pollutantto a derivative product having a characteristic electrochemical activity and a sensing means responsive to the electrochemical activity of the product and including signal means providing a signal indicative of the product and therebythe pollutant. The derivative pro- duct results from the chemical change in the pollutantwhich may occurfrom the oxidation orother process on the pollutantto eitherform electrochemical activity or change the existing activity of the pollutant. A particularly useful combination forthe de- vice includes a noble metal heating means.,fvhich also operates as a sensor providing a signal at concentrations of the pollutant above about 0.1-1.0% while providing the derivative product overthe overall concentration range for detection bythe elec- trochemical sensing means. The presence crabsence of the signal from the noble metal heating means in combination with the signal from the electrochemical sensing means may be used in determining the presence or absence of a pollutant and its general concentration range.
The derivative productfrom the pollutant exhibits a characteristic electrochemical activitywhich may be detected bythe sensing means at levels as low as about one ppm. These products may bethe oxides of carbon, sulfur, nitrogen andthe like having electrochemical activity and other compositions indicative of partial oxidation or decomposition of the pollutant.
The device of Figure 1 includes the catalytic heat- ing means as illustrated by a hot-wire sensor arranged to receive a sample of the ambient gas and sensing means illustrated by an electrochemical sensor arranged to receivethe derivative product. The conversion means may include a signal meansfor prov- iding a signal apartfrom the signal from the sensing means. The hot-wire sensor includes a heating means and a catalyst such as one or more of the oxidation catalysts. In general, hot-wire sensors and catalysts based on Pt, Pcl, Rh and Au are particularly useful. Also useful maybe catalysts comprising lror 2 GB 2 184 244 A 2 Ag, or various noble metal alloys, such as Pd-Ag, Pt Rh, Pt-lrorAu-Ag, or a compound, especially an oxide, of one of said metals. The hot wires orfila ments maybe either made of a pure noble metal or, preferably, be coated on a suitable baser metal or alloy. The catalysts may also be dispersed on a sup portsuch as C, Si or alumina. As the sample is ex posed tothe hot catalyst, it is chemically changed and preferably oxidized or decomposed to at least one derivative productwhich may be detected bythe electrochemical sensor.
The electrochemical sensor is responsiveto low levels of the derivative product and provides a signal indicative of the product and therebythe pollutant.
Whilethe electrochemical sensor is responsiveto some electrochemically active substances atthese low levels, its responseto compounds such as be n-,yi chloride and the like which are not primarily characterized by electrochemical activitytends to be so limitedthat it may not be used fordetection un less aided by one of the above-mentioned oxidation catalysts.
Suitably, the electrochemical sensor may be a con stant-potential amperometric sensor. As the derivat ive product is sensed, a signal is generated indicative of the electrochernical activity atthe "working elec trode" of the sensor. In general, the hotwire sensor representing the conversion means and the ampero metric chemical sensor representing the sensing means are sufficiently small thatthey may be built into a single unit where the derivative productfrom 1he hot wire sensor may interactwith the electro chemical sensorwithin the same unit. Preferably, the sample is introduced into a sample channeling arrangement by which the sample is first introduced 100 to the hot-wire sensor. The derivative productfrom the hot-wire sensor is then routed to the electro chemical sensor either directly, but in a controlled manner, so as to enhance the activity of said sensor byraising its temperature to a preferred value or through a baffle arrangement orother isolation system sathatthe electrochemical sensor need not be directly exposed to the heaterof the hot-wire sensor.
In Figure 1, an exploded view of the invention is illustrated showing a path including a baffle arrangementto isolatethe electrochemical sensorfrom the heaterof the hot-wire sensor and thereby reducethe possibility of damageto the electrochemical sensor.
The inventive device includes electrical heating means with a noble metal surface exposed to the gas for heating the gas and catalyzing the combustion of the pollutaritto provide a derivative product having a characteristic electrochemical activity and electro- chemical sensing means responsiveto that activity or providing a signal indicative of that activity. As illustrat ted in Figure 1, the heating means is provided by a filament 10 composed of a heating elementcore 12 and a noble metal surface 14 mounted in a reac- Vion chamber 16 of block 15. A sensing element 18 is mz3tjr2ted in chamber 20 of block 19 for detecting the activity of the product derived from the cimbustion of the pollutant. A reference electrode 22 and a counter electrode 21 are also provRic-d. Siocks 15 and 19 are joined by block 23 with chamber 24. Inlet 26, outlet 28 and chambers 16 and 24 provide channeling means for exposing the gas to the heating filament 10 and the derivative productto the sensing element 18. Closure member 30 prov- ides sealing of chamber 20. A pluggable opening 32 above chamber 20 permits introduction of electrolyte into the electrochemical sensor.
In another embodiment of the invention, shown in Figure 2, a diffusiontype electrochemical sensor is used to detect concentrations of 0-2.40/6 methane in air by preexposing any ambientgas diffusing orconvecting towards said sensorto an iridium- coated filament heated to a temperature of 300-600'C and preferably 400- 500'C. Thefilament is made preferably of a metal or alloy of relatively high resistivity having a coefficient of thermal expansion closeto thatof iridium, e.g., commercial grade titanium. By adjusting thefilament length and cross-section to yield a resistance of about 2,000 ohms andtemperature of 400-500'Cwhen heated by a current of about 10 milliamperes, it becomes possibleto achieve a lowpower low-current-drain methane detector suitable for intrinsically safe mine-monitoring applications.
In Figure 2the device 36 includes heating filament 38 mounted in housing 37 with electrochemical sensing element40 hidden from direct exposureto filament 38 by barrier42 of glass woof or othersuitable porous material. In Figure 2, inlet 52, vent 46, and channels 48,49 and 50 provide channeling of the gas and derivative product. A source of electrical current is provided by leads 54 and 56 passing through a ceramic plug 44to filament 38.
The heating of the iridium-coated filament of Figure 2 is preferably governed by a temperature controller, such as that shown in the block diagram of Figure 3. To further reducethe heating power requirements, thefilament may be heated in intermittent pulses, e.g., in pulses of 0. 5to 3 seconds'duration every 10 seconds. In general, the response time of the device is less than about 20 seconds. The heating pulses are sufficientto bring the peakfilament temperature upto the range of 400500'C.
it is noteworthythat electrochemical sensors when used bythemselves such asthat used in the device of Figure 2, do not usually respond to methane even in concentrations as high as 100%. Yet the signals obtained with the heated iridium filament permit easy measurement of methane concentrations as low as 0.05% or less.
As an illustration of the general flow diagram associated with the detection process, Figure 3 illustrates an arrangement where the derivative product may be automatically routed through a multipath solenoid valve or other diversion meansto eitherthe electrochemical sensor or removed from the device before exposure to the sensor depending on the concentration levels. In this flow arrangement, the signal from the hot-wire sensor may serve to indicate the presence of the pollutant at a concentration above about 0.5-1.0% and may be used to directthe flow of derivative product awayfrom the device to avoid the possible effects of an excessive concentration of certain pollutants on the electrochemicai sensor.
When no signal from the hot-wire sensor is prov- ided, the flow pattern will be used to directthe deri- 3 GB 2 184 244 A 3 vative product to the electrochemical sensor and its signal will provide an indication of the presence of the derivative product and therebythe pollutant. With a combination of signals, the presence of the pollutant and its concentration may be determined.
The general flow pattern of the gas and derivative product are illustrated in Figure 3. As illustrated, a gas sample is admitted via line 60to conversion chamber 62 having filament 64whose temperature is controlled by controller 65. Signal indicating means is provided by indicator 66 to provide any signal availablefrom filament 64. The derivative product is channeled via line 68, valve 70 and line 72to the electrochemical sensor74 having a signal indicator76.
Pump 78 provides the suction and determinesthe flow rate within the device. Controller65 and valve 70 are governed by a microprocessor (computer/ controller) 79 which receives the signaisfrom indicator 66 and 76.
As an illustration of the representative perform- ance of the above-disclosed embodiments, Figure 4 provides response curvesfor benzene. In general, benzene is not readily detected on electrochemical sensors at ppm levels and is further essentially un detectable by a hot-wire sensor at ppm levels. How ever, by combining the two different sensors, it is possible to produce signals indicative of the pres ence of benzene at a concentration of less than 100 ppm level in air. While benzene at such levels is not detectable by hot-wire or heated semiconductor sen- 95 sors, the heated catalytic surface of such sensors or other noble metal-coated filaments converts the ben zene to one or more oxides of carbon or degradation products which are then detected by the electro chemic?l sensor.
In Figure4A,the heated filamentwas made of a fine platinum wire (0.08 millimeterin diameter) sim ilartothatused in hot-wire flammable gas sensors, heatedto atemperature of about 1000'C. Thetwo humps starting at about 1.5 minutes and 4minutes correspondto exposureto samples of 200 ppm and ppm of benzene, respectively. In Figure4B, a com mercial tin oxide semiconductor sensor, heatedto bout300'C,was used as a conversion means.The three humps starting at about 1 minute, 6 minutes, and 10 minutes correspond to samples of 200 pprin, ppm, and 200 ppm of benzene, respectively. In Figure 4Qthe conversion device consisted of a fine (0.03 millimeter in diameter) gold filament heated to 950-50'C, and the hump starting at about 0.6 minute was dueto a sample of 200 ppm of benzene. The same electrochemical sensor, comprisirig a plat inum blacksensing electrode at a potential of about 1.1 volt relativeto the standard reversible hydrogen electrode, was used in all three cases. Acomparison of the ordinates of Figures 4A, B, and C showsthat the heated tin oxide yields an approximately three to fourtimes higher response than the platinum fila merit, butthatthe gold filamentyields a three-fold higher responsethan the tin oxide and a ten times higher responsethan the platinum.
Other representative compounds which do not appearto be detected by eithertype of sensor inde pei,)dent!y but are bythe two sensors in combination at concentrations of about 100 ppm or less are benzyl chloride and tetrachloroethylene.
The following example is provided for illustrative purposes and is not intended to be restrictive asto the scope of the invention:
Examplel
A sample of air containing 200 ppm of tetrachloroethylene was tested in an apparatus having a catalytic bead sensor available f rom Rexnord Corporation of Sunnyvale, California and a Pt-catalyzed COfilament availablefrom Energetics Science of Hawthorne, NewYork. The sample was tested with each element operating separately. Observed currentsfrom each sensoroperating separatelywere indistinguishable from normal noise levels. In another test, a similarly constructed electrochemical sensor in combination with a Pt-catalyzed COfilamentwas used foran airsample containing only 20 ppm tetrachloroethylene. Asignal of aboutO.3 microampswas observed forthe combination of sensors as compa- red to a value of lessthan 0.2 (noise level) microamps without the filament.
As described above,the invention provides a useful device for detecting a gas,vapor, chemical pollutantor othercomponent in a gaseous medium and iscapable bya combination of a catalytic heating element and an electrochemical sensor of detecting the component at low concentrations.
Claims (8)
1. A device for detecting a component of an ambient gas comprising:
conversion means for chemically changing said component to a derivative product having a char- acteristic electrochemical activity, said conversion means having a first means for generating a signal when said component is present in a concentration above about 0.1 - 1.0%, but essentially unresponsive at concentrations below about 0.1 %, and sensing means responsive to the electrochemical activity of said product for concentration of said component below about 0.1 % for providing a signal indicative of the product and therebythe component.
2. A device as claimed in claim 1, including means for receiving the signals from said conversion and sensing means and determining the general concentration of said component.
3. A device as claimed in claim 1 or2, where said conversion means is a hot wire sensor having a surface of an oxidation catalyst.
4. A device as claimed in claim 1, 2 or3,wherein said sensing means is an electrochemical sensoroperative with oxidized gases of organic compositions.
5. A device as claimed in claim 1 or 2, wherein said conversion means is a semiconductor sensor.
6. A device as claimed in claim 5, wherein said semiconductor is a metal oxide.
7. A device as claimed in claim 6, wherein said metal oxide is tin oxide or a mixture thereof.
8. A device for detecting a component of an ambient gas, substantially as hereinbefore described and exemplified.
Printed for Her Majesty's Stationery Office by Croydon Printing Company (U K) Ltd,4187, D8991685. Published by The Patent Office, 25Southampton Buildings, London, WC2A lAY, from which copies maybe obtained.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US58572184A | 1984-03-02 | 1984-03-02 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8629014D0 GB8629014D0 (en) | 1987-01-14 |
| GB2184244A true GB2184244A (en) | 1987-06-17 |
| GB2184244B GB2184244B (en) | 1988-04-07 |
Family
ID=24342673
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08503514A Expired GB2155184B (en) | 1984-03-02 | 1985-02-12 | Combined sensor device for detecting toxic gases |
| GB08629014A Expired GB2184244B (en) | 1984-03-02 | 1986-12-04 | Device for detecting a component of an ambient gas |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08503514A Expired GB2155184B (en) | 1984-03-02 | 1985-02-12 | Combined sensor device for detecting toxic gases |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS60205348A (en) |
| CA (1) | CA1261720A (en) |
| DE (1) | DE3507385A1 (en) |
| FR (1) | FR2560685B1 (en) |
| GB (2) | GB2155184B (en) |
| IT (1) | IT1184147B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2482335A (en) * | 2010-07-30 | 2012-02-01 | Thermo Electron Mfg Ltd | Combustion analyser with sensor for indicating incomplete combustion |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3624509A1 (en) * | 1980-09-26 | 1988-06-30 | Maria Gyulai Dr Dobosne | Arrangement and process for detecting halogen-containing compounds |
| DE3729286A1 (en) * | 1987-09-02 | 1989-03-16 | Draegerwerk Ag | MEASURING DEVICE FOR ANALYZING A GAS MIXTURE |
| GB8804717D0 (en) * | 1988-02-29 | 1988-03-30 | Atomic Energy Authority Uk | Gas sensing |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2812613C2 (en) * | 1978-03-22 | 1983-12-15 | Bayer Ag, 5090 Leverkusen | Electrochemical cell |
| GB2034893A (en) * | 1978-11-17 | 1980-06-11 | English Electric Valve Co Ltd | Combustible gas detector |
| IT1145264B (en) * | 1979-03-15 | 1986-11-05 | Ricardo Consulting Eng | APPARATUS AND PROCEDURE FOR DETERMINING THE CONCENTRATION OF THE AIR / FUEL MIXTURE SUPPLIED TO AN INTERNAL COMBUSTION ENGINE |
| DE3118936C2 (en) * | 1981-05-13 | 1985-07-04 | Drägerwerk AG, 2400 Lübeck | Use of a measuring method for gaseous or vaporous media and a device for this |
| GB2099588B (en) * | 1981-05-28 | 1985-10-30 | Nat Res Dev | Fluid component measuring and alarm device |
| US4433922A (en) * | 1982-07-02 | 1984-02-28 | The Babcock & Wilcox Company | Calorimeter |
-
1985
- 1985-02-12 GB GB08503514A patent/GB2155184B/en not_active Expired
- 1985-02-13 CA CA000474247A patent/CA1261720A/en not_active Expired
- 1985-02-28 FR FR858502975A patent/FR2560685B1/en not_active Expired
- 1985-02-28 JP JP60040238A patent/JPS60205348A/en active Pending
- 1985-03-01 IT IT19721/85A patent/IT1184147B/en active
- 1985-03-02 DE DE19853507385 patent/DE3507385A1/en not_active Ceased
-
1986
- 1986-12-04 GB GB08629014A patent/GB2184244B/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2482335A (en) * | 2010-07-30 | 2012-02-01 | Thermo Electron Mfg Ltd | Combustion analyser with sensor for indicating incomplete combustion |
| GB2482335B (en) * | 2010-07-30 | 2012-09-19 | Thermo Electron Mfg Ltd | Apparatus and method for combustion analysing a sample |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2184244B (en) | 1988-04-07 |
| GB8503514D0 (en) | 1985-03-13 |
| FR2560685B1 (en) | 1989-05-12 |
| GB8629014D0 (en) | 1987-01-14 |
| GB2155184B (en) | 1988-04-13 |
| IT8519721A0 (en) | 1985-03-01 |
| DE3507385A1 (en) | 1985-09-05 |
| JPS60205348A (en) | 1985-10-16 |
| CA1261720A (en) | 1989-09-26 |
| GB2155184A (en) | 1985-09-18 |
| FR2560685A1 (en) | 1985-09-06 |
| IT1184147B (en) | 1987-10-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19970212 |