Abstract:
An imbedded Internet sensor system for protecting real property from the consequences of subterranean chemical pollution. The system provides real time monitoring of the first occurrence of contaminants in the subsurface of a property. An onsite processor controls a local network of sensors and a communication device relays the data to a remotely located database. The local network of sensor are made up of multiple acoustic wave sensors differentiated by sensor coatings configured into a sensor array. As a vapor contaminant passes across the surface of the surface acoustic wave sensor crystals, a shift is caused in the frequency of the acoustic wave. The shift is translated into an electronic signal that is communicated to the onsite processor, which in turn communicates the signal in the form of electronic data to a remote facility wherein remedial measures may be dispatched and appropriate parties notified. The method of dispatch and notification is provided by a Web site system accessible through the Internet. The system is provided as part of a pollution detection and notification service for which a customer pays a subscription fee.

Description:
FIELD OF THE INVENTION 
     This invention relates to pollution detection. Specifically, this invention relates to a system and method for automated remote detection and reporting of subterranean pollutants in liquid and gaseous form. 
     BACKGROUND OF THE INVENTION 
     Environmentally harmful chemicals are commonly utilized in industrial and commercial processes. Similarly, chemical wastes are commonly stored in man made storage tanks, containers and reservoirs. Although precautionary measures and controls such as impermeable liners are generally used, leaks or spills from such systems are common, resulting in migration of harmful materials into the subsurface soil and groundwater. Many release events go unidentified by the property owner and are not discovered until contaminants have spread a considerable distance from the source. Such pollution scenarios can result in property devaluation, regulatory compliance issues, legal challenges, and costly remediation requirements. Early detection and response to such spills and leaks can substantially reduce liabilities to such property owners. 
     In the past, environmental monitoring systems have been devised to detect leaks and fugitive emissions from various storage systems, processes, and conduits. Many such methods offer means of detecting release events, however there are presently no known efficient methods employed for, remote, real time monitoring of chemical releases to the subsurface. In particular there is no known means of automated remote, real-time monitoring for early detection of low level concentrations of volatile organic compounds (VOCs) associated with commercial facilities such as dry cleaners, printers, and automotive servicing facilities. 
     Without the means of continuous remote monitoring, it is the current practice to detect and quantify potential subsurface contamination by means of cumbersome investigative and subsurface sampling techniques that requires both onsite sampling and off-site analytical testing for contaminants and their concentrations. 
     There have been systems devised for environmental monitoring of fugitive chemical emissions from piping, as described in “Reversible Sensor for Detecting Solvent Vapors,” U.S. Pat. No. 5,417,100 issued to Miller, et al. Similarly there are methods for measuring in line process gases, as described in “Continuous Monitoring of Organic Pollutants,” U.S. Pat. No. 5,435,169 issued to Mitra. However, such methods were not developed or applied to the monitoring of chemical migration to the subsurface environment. 
     Additionally, leak detection methods, as described in “System for Detecting Leaks from Liquid-Containing Reservoirs and Conduits,” U.S. Pat. No. 4,404,516 issued to Johnson, have been devised for monitoring storage tanks and reservoirs. However, those methods are limited to on-site systems that require facility operator response. 
     Other environmental monitoring systems have been devised for monitoring of chemical fugitive emissions at large industrial facilities. One such system, as described in “Soil Pollution Monitoring System,” U.S. Pat. No. 4,618,855 issued to Harding, et al., actively pumps gases from the subsurface of the facility past a sensing device in order to detect the presence of vapor. This system relies on a vacuum pump to draw air and leakage gases through the ports and past sensors which detect the presence of gasoline, carbon monoxide, methane, ethanol, and other vapors. Accordingly, a ducting mechanism is required to force fresh air by the sensors periodically so as to clean the sensors before a new reading can be taken. 
     Environmental monitoring systems, as described in “Environment Monitoring System,” U.S. Pat. No. 5,892,690, issued to Boatman, et al., utilize a data acquisition system for collecting and recording air quality data from remote locations. The data is accumulated and stored into a comprehensive database. 
     However, existing methods are not designed to monitor multiple facilities from a remote location with the capability of real-time detection of subterranean pollutants coupled with immediate notification to a third party of such a detection. 
     The present invention addresses these and other problems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system and method for automated remote real-time detection and reporting of subterranean chemical pollutants. The system is provided as part of a remote real time pollution detection and reporting service, particularly for customers owning, or responsible for, property where volatile organic compounds (VOC) are stored or utilized. 
     The system of the present invention includes a series of sensors placed in strategically located underground cavities beneath a property to detect chemical contamination caused by the release of chemical pollutants into the subsurface soil and groundwater. The relative placement of the sensors is determined by a number of factors. These factors include the rate of vapor flow diffusing through the native soil of the property, the volatility of the particular chemicals likely to be released on the property, and the location of likely sources of the chemical contaminants. These and other factors are well known in the art, and have been utilized in the past for determining the locations for collection of representative samples. 
     In accordance with one aspect of the invention, the sensors are housed within a perforated housing seated within a cavity beneath the surface of a property. The cavity functions as a mass flux chamber in order to maximize sensor response. The cavity is filled with a high porosity media, so as to provide separation between the native soil and the sensors, while minimizing resistance to the migration of chemical vapors to the sensors. Additionally, the high porosity media increases the surface area of contact between the subsoil and the sensors. The high porosity media may be glass or sand, although other materials well known in the art may be used in the alternative. The mass flux cavity facilitates the detection of the rate of change in concentrations of vapors migrating by diffusion through the soil environment. 
     In another aspect of the invention, a semi-permeable membrane surrounds the perforated housing. The membrane is utilized when the sensors are required to be placed in a moist or wet subsurface, for example in an area having a high water table. The membrane prevents liquids, such as water from penetrating through the housing into the sensor, while still allowing chemical vapors to pass through. This protection is necessary since liquid contact with the sensors may also skew any readings made by the sensors, and thus affect the accuracy of the chemical detection. 
     In a preferred embodiment, there are multiple sensors housed as an array within each perforated housing. The type of sensors used may vary, but are preferably of the type known as surface acoustic wave (SAW) sensors. A SAW sensor is a mass sensitive sensor that transmits an electric signal at a frequency which is effected by the presence of a particular chemical or chemicals. When a change in mass occurs at the surface of the sensor, the frequency of the signal changes accordingly. Among the SAW sensors contained in the array may be a reference sensor having a fixed operating frequency in the range of 100 MHz to 400 MHz. The remaining SAW sensors are selectively coated so as to react to various chemical vapors likely to be detected in the event of a leak on the property. The chemical selectively forms a weak bond to the coating in a process known in the art as sorption. Each sensor has a normal operating frequency, determined by the characteristics of the coating utilized. As a particular chemical vapor travels across the sensor, it attaches to the selective coating, changing the effective mass of the coating, which in turn alters the operating frequency of the sensor. 
     An important benefit of SAW sensors is their durability and reliability. Their operating frequencies and responses are initially set by a photolithographic process. The photolithographic process is a process known in the art for producing integrated circuits and printed circuit boards by photographing the circuit pattern on a photosensitive substrate and then chemically etching away the background. The SAW sensor frequency is generated at the site by oscillator circuits. As such, these sensors do not require tuning operations nor do they become de-tuned in the field. Additionally, the sorption process allows the sensor to be reusable, as the weak bonds formed with the chemical are easily broken by the introduction of heat. Thus the sensor is capable of functioning as a reusable event detector. 
     The composite acoustic response of the sensor array can be likened to a fingerprint. SAW sensors fall under the category of “smart sensors” that are capable of identifying the specific components as well as the concentration of a particular chemical within a sample. Conventional detectors, such as metal oxide semi-conductors, produce a broad response to a class of chemicals and physical conditions. In practice, conventional detectors alone often give false positive detection readings of a chemical leak. Consequently, an on-site visit and chemical analysis is required to confirm the reading. The use of SAW sensors facilitates the reliable and automated remote detection of specific chemical pollutants in a subsurface described in the present invention. 
     The preferred embodiment also includes an onsite computer processor connected to the various sensor arrays, which acts as a sensor interface. The computer processor has embedded within it software capable of reading the acoustic response, or fingerprint, of the SAW sensors. Additionally, a database is accessible by the software for identifying the specific sensor fingerprint of the chemical being detected by the sensor. The database may be stored within a data storage device housed within the computer, or be located on a remote computer, accessible by various means including the Internet. As such, the computer processor connects to a remote server computer, located at a remote monitoring station, that receives data from the onsite processor and may automatically report detection of a chemical release to a designated party. The software also provides a means for calibrating the sensors, performing functional status checks, and setting appropriate response thresholds from the remote server. 
     An important benefit of the onsite computer processor integrated with a remote server is the capability of continuous and automated monitoring of the property from a remote location. The utilization of a sensor array having SAW sensors, or a similar sensor device, in combination with a computer processor eliminates the need for onsite visits to the property to take samples from alternate sensing devices, which would usually require an offsite laboratory analysis. 
     The use of a remote monitoring station allows for immediate and automated monitoring of various sensor arrays located at multiple properties. When utilized as part of a pollution detection service, the remote monitoring station facilitates the immediate notification to third parties of a chemical pollutant in the subsurface of a property. The third party may be the owner of the property, or another designated entity responsible for responding to a chemical leak. In the preferred embodiment, this notification is provided as part of a subscribed service. 
     The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention as will be described. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the following Detailed Description of the Invention, which includes the preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the invention will now be described with reference to the drawings of certain preferred embodiments, which are intended to illustrate and not to limit the invention, and in which: 
     FIG. 1 is an architectural drawing and flow diagram illustrating the primary components of a system that operates in accordance with the present invention. 
     FIG. 2 is a graphical representation of the relationship between VOC concentration and time. 
     FIG. 3 is a cross sectional view of the on-site portion of the system utilized in accordance with the present invention. 
     FIG. 4 is a close up perspective view of the sensor array that operates in accordance with the present invention. 
     FIG. 5 is a flow diagram illustrating the chemical detection and reporting sequence in accordance with the present invention. 
     FIG. 6 is a flow diagram illustrating the sequence of steps required to retrieve and report data by the onsite processor of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following description, certain terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements 35 U.S.C. 112, but it is to be understood that the same is not to be limiting and should not be so construed in as much as the invention is capable of taking many forms and variations within the scope of the appended claims. 
     The present invention is a system for automated remote detection and reporting of subterranean chemical pollutants in the subsurface of a property. 
     Referring now to FIG. 1 in particular, there is illustrated the primary components of a system that operates in accordance with the present invention. The system includes multiple sensors  10  located beneath the surface of a real property  12  wherein detection of subterranean chemical pollutants is desired. The sensors  10  are arranged in an array  14  connected to a sensor interface  16 . The sensor interface  16  may be a computer processor, utilizing embedded software, located on the site of the real property  12 . The computer processor may also be networked to other processors at other sites, that interface with a computer server  19  located at a remote monitoring station  18 . As utilized herein, the terms computer server and sensor interface are used to describe a model of interaction in a distributed system in which a program at one site sends information to a program at another site and waits for a response. The requesting program at the site is the software utilized by the sensor interface and the program which responds and reacts to the information is called the “server.” Communications lines  17 , such as telephone lines or broadband cable connect the various sensor interfaces  16  with the remote monitoring station  18 . Various other means known in the art for long range transport of data may also be utilized, examples of which may include satellite relay or wireless digital communication. 
     When a chemical pollutant is detected by the sensors  10  on the property  12 , the sensor interface  16  processes the data generated by the sensors and communicates this information to the remote monitoring station  18 . The chemical pollutant is detected when the sensor interface  16  identifies a significant change in concentrations of vapors migrating to the sensors  10 . Following the release of a contaminant to the sub-surface, contaminant concentrations at the release point skyrocket from trace levels to extremely high concentrations approaching the vapor pressure of the contaminant. The contaminant vapor then spreads into the soil environment by gaseous diffusion. The rate of change in concentrations of vapors migrating by diffusion can be described to those skilled in the art by Fick&#39;s Second Law. The following relationship is a one-dimensional expression of Fick&#39;s Law:            δ                 C       δ                 t       =     D            δ   2        C       δ                   x   2                                  
     Where C=vapor pressure concentration, 
     t=time, 
     D=effective diffusion coefficient, and 
     x=distance from the source of the vapor; such that          δ                 C       δ                 t                            
      is the change in vapor pressure concentration over time, and            δ   2        C       δ                   x   2                              
      is the derivative of concentration gradient over distance. 
     A solution to the partial differential equation is an exponential function: 
     
       
         C (x,t) =C 0 erfc( x /2( Dt ) ½ ) 
       
     
     where, erfc is the complementary error function. 
     A graphical presentation of the rate of change in concentration at a distance of six feet from a contamination source location is illustrated by way of example in the graph shown in FIG.  2 . 
     The graph  2  illustrates the logarithmic relationship  4  between concentration at time (t) over concentration at time (t 0 )  6  and time as measured in days  8 . Such steep changes in sensor  10  response are strictly attributable to migration of vapors in response to a subterranean pollution event. Other potential patterns in sensor  10  response which are not indicative of pollution events are discernable from a pollution event because they do not present such a logarithmic relationship  4 . By way of example, diurnal changes in temperature may produce a cyclical relationship, differentiated by the logarithmic relationship  4  indicative of a pollution event. 
     Referring again to FIG. 1 the server  19  located at the remote monitoring station  18  utilizes a computer program  20  to process the data received from the sensor interfaces  16 . The program  20  identifies the rate of change in concentration of migrating vapors and the composition of the chemical detected by the sensors  10  by analyzing the data retrieved by the sensors  10  in comparison with a sensor response database  21 . The sensor response database  21  may include a library of sensor responses to known mixtures of vapors and a library of historical sensor responses at the particular site. Additionally, the computer program  20  may contain an algorithm designed to interpret the responses as release events, when analyzed with the data contained in the database  21 . The server  19  transfers this data to a Web site system  22  for electronic notification to a responsible party  24  such as the owner of the property  12  or other designated entity. The electronic notification is processed through the Internet  23  to an email address of the responsible party  24 . In the alternative, the responsible party  24  may access the Web site system  22  using a secure and confidential Internet  23  connection where detection reports of the property  12  are periodically updated. The remote monitoring station  18  may also dispatch appropriate remedial measures to counteract the leak that has been detected. 
     The Web site system  22  is a computer system that serves informational content over a network using the standard protocols of the World Wide Web. The Web site corresponds to the particular Internet domain name utilized by the detection service provider described herein, and includes content associated with the particular detection service provider. As used herein, the term Web site system is generally intended to encompass both the server components that serve the informational content over the network, and the back end components that interact with the server components to perform services for Web site users. 
     The term Internet as used herein is used to describe a collection of interconnected networks that are linked together by a set of standard protocols to form a global, distributed network. While this term is intended to refer to what is now commonly known as the Internet, it is also intended to encompass variations which may be made in the future, including changes and additions to existing standard protocols. 
     Although the embodiment described herein uses Web technology and the Internet to post and communicate pollutant detection, any of a variety of communication means can be utilized to transmit the notification of pollution detection. For example, the remote monitoring station  18  may transmit a facsimile message to the responsible party  24 , or telephone call, or overnight mail. These means of notification are meant to be illustrative and are not intended to be limiting. The notification is provided as part of a subscribed service provided by the remote monitoring station  18 , for which the owner of the property  12  or other desiring entity pays a subscription fee. 
     As further illustrated in FIG. 3, the sensors  10  are seated within a cavity  30  strategically located in the subsurface of the property where detection of a chemical pollutant  26  is desired. The strategic location of the sensors  10  is determined by a number of factors. These factors may include the rate of diffusive migration through the native soil of the property  12 , the volatility of the particular chemicals likely to be released on the property  12 , and the precise location of the potential leak source. These and other factors are well known in the art, and have been utilized in the past for determining the location of placement of sampling locations for soil vapor. 
     The sensors  10  are housed within a perforated housing  28  that is seated within the cavity  30 . The perforated housing  28  may be made of a mesh like material that acts to separate the sensors  10  from the surrounding materials, while still permitting vapors to pass through to the sensors  10  unimpeded. The cavity  30  acts as a mass flux chamber that facilitates the flow of chemical vapors  36  to the sensors  10 , while also providing a means of separating the sensors  10  from the surrounding soil. The cavity  30  may be filled with a high porosity media  34 . The function of this media  34  is to prevent direct contact of the sensors  10  with the surrounding native soil. However, it should be noted that the high porosity media  34  should be of a particular material such that the migration rate  36  of a polluting chemical  26  is not impeded. Additionally, the high porosity media  34  increases the surface area of contact between the subsoil and the sensors  10 . The material to be used may include glass or sand, however it is to be understood that other similar high porosity mediums well known in the art may be utilized to fill the cavity  30 , such that a mass flux chamber is created. 
     The cavity  30 , acting as a mass flux chamber, magnifies the expected rate of change (shown by example in FIG. 2) by exposing a large surface area to native soils, possessing a relatively small internal volume, and being closed to potential contaminants such as surface air that would interfere with sensor  10  detection. Pollution events occurring in the presence of low levels of contaminant vapor, as in locations where a pollution event occurred in the past, display the rapid initial rates of change illustrated in FIG. 2 by utilization of the sensors  10  within a mass flux chamber described in the present invention. 
     The housing  28  may sit on a push point  32  that may be used to create the cavity  30 . The push point  32  may be a conically shaped solid metallic object commonly used in the art for creating a cavity when driven into a surface. The push point  32  provides a self-boring means for creating the cavity  30  as well as provides a stable surface on which the housing  28  may rest. Additionally, the push point  32  provides an air tight seal to the bottom of the cavity  30  such that other underground vapors may not diffuse upward to the sensors  10 . Although the use of a push point  32  is advantageous, other means known in the art for creating an air tight cavity in the subsurface may also be utilized. Such means may include drilling a hole in the surface and thereafter sealing the bottom with an air tight sealer such as caulk or cement. 
     It is important that the cavity  30  be sealed from the surface, so as to prevent interference with vapors that may be present in the above-surface air. Accordingly, an impermeable sealing compound  38 , such as caulk, may be utilized to seal the opening of the cavity  30  above the housing  28 , and below the surface of the property. Other materials similar to caulk and well known in the art may also be utilized to place an air tight seal above the cavity  30 . Similarly, a vapor tight access port  40  utilizing an O-ring  42  for additional assurance of an air tight seal, may be placed above the cavity  30  on the surface of the property. The access port  40  provides a means for accessing the sensors  10  and housing  28  for any desired repair or adjustment. Additionally, the access port  40  provides access to a vapor sampling port  44 . The vapor sampling port  44  provides access to the sensors  10  in the event that a manual sampling is desired. The sampling port  44  has a stop valve  46  to assure that polluting vapors  36  do not accidentally or incidentally escape between manual sampling intervals. 
     Although manual sampling may be desired from time to time, a novel aspect of the present invention is the utilization of a remote computer system to monitor the sensor  10  activity. This remote monitoring is accomplished by networking multiple sensor interfaces  16  that are coupled to the sensors  10 . The means of coupling an electronic sensor  10  to the sensor interface  16 , which may be a computer processor, are well known in the art, and include wireless (not shown) or wire connections  52 . The sensor interface  16  provides a means for monitoring and calibrating the sensors  10  from a remote location by communicating with a server  19  (shown in FIG. 1) on the remote location via various client-server connection methods well known in the art, including a RS-232 port  54 , a parallel port  56 , or wireless interface  58 . It is to be understood that various alternative client-server connection methods may utilized herein, and may include connections commonly known in the art as telephone jacks, Ethernet ports, and modem antennas. Additionally, a serial port  60  may be provided so that a technician may perform an onsite analysis of the data retrieved by the sensors, by attaching a secondary processing device to the serial port  60 . Such devices are well known in the art and include laptop computers, and miniaturized computer processors commonly sold under the trademark “Palm Pilot.” A power port  62  may be provided on the interface  16  so as to supply the sensor  10  with electrical current. Although, alternate power supplies well known in the art may also be utilized, including battery and solar power. 
     When the present invention is utilized within a wet subsurface environment, it is necessary to protect the sensors  10  from coming into contact with any surrounding water, or other ambient liquid. In this application, the sensor housing  28  may be enveloped by a semi-permeable membrane  48 . This prevents liquids from penetrating through the housing  28  while still allowing chemical vapors  36  to pass through. Various materials well known in the art may be utilized as the membrane  48 , such that a liquid medium is prevented from penetrating through the membrane  48  but gaseous vapors are allowed to pass with minimal resistance. This protection is necessary as liquid contact with the sensors  10  may skew the readings made by the sensors, and thus effect the accuracy of the chemical detection. 
     FIG. 4 illustrates a close up perspective view of the sensors  10  that operate in accordance with the preferred embodiment. The type of sensor  10  illustrated and preferred is a surface acoustic wave (SAW) sensor. Alternate conventional detectors well known in the art, such as metal oxide semi-conductors that produce a general response to numerous chemicals and physical conditions, may also be used. However, the use of SAW sensors is preferred because it facilitates the automated remote detection of chemical pollutants  26  in a subsurface described in the preferred embodiment and is more reliable than alternate sensors, such as metal-oxide sensors. Additionally, SAW sensors may operate at low temperatures, which limits interfering effects of the surrounding soil, including regular heating and drying of the soil, as well as the thermally induced convective movement of inert soil gases. These interfering effects can skew results when utilizing convention sensors, leading to undependable interpretations. The sensors  10  are arranged in a sensor array, which includes one or more SAW sensors  10   b  and at least one reference SAW sensor  10   a . The SAW sensor produces an acoustic wave  64  that travels across the sensor. The frequency of the wave is initiated by an oscillator circuit  84 . A series of interdigital transducers (IDTs)  66  are placed on the piezoelectric substrate  67  of the sensor  10 . IDTs  66  are a series of collinear electrodes, well known in the art, that are placed on the piezoelectric substrate  67  for the precise purpose of launching a surface acoustic wave. Although the use of a piezoelectric substrate  67  is preferred, other substrates known in the art that possess a noncentrosymmetric crystal structure capable of generating an electric charge on the application of a mechanical stress may be used. 
     In the preferred embodiment, the reference sensor  10   a  will have a surface acoustic wave  64  of a predetermined frequency in the range of 100 MHz to 400 MHz, initiated by the oscillator circuit  84 , so as to distinguish it from the other sensors  10   b  in the array. The other sensors  10   b  in the array are coated with a selective coating  68  for attracting a specific chemical vapor whose detection is desired. The selectively coated sensors  10   b  are calibrated to produces a surface acoustic wave  64  of a different frequency than that of the reference sensor  10   a . As the particular chemical vapor in question comes into contact with the selective coating  68  of the sensor  10   b , the mass of the sensor changes. Accordingly, the surface acoustic wave frequency is altered. The rate of change of the vapor concentration, as detected by the frequency change in the SAW sensors  10  and described by Fick&#39;s Law above, allows the sensor interface  16  and server  19  to immediately identify the nature of the pollution event. 
     The selectively coated sensors  10   b  bind with the chemical vapors by a process known in the art as sorption. Sorption interactions are generally weak physical bonds of less than about 40 kJ/mole. Bonding forces in this range are similar in energy to heats of condensation. Sorption can be reasonably expected under conditions that favor condensation, such as low surface temperatures. Similarly, as in evaporative processes, the desorption of the selected chemical vapor can occur, which makes the surface interaction reversible. As such the selectively coated sensors  10   b  are reusable, as controllable environmental aspects such as temperature, may be altered to allow the desorption of the VOCs. 
     The coatings of the sensors  10   b  are typically organic films with an affinity for a target VOC that is generated by the presence of functional groups on the coating that interact selectively at temperatures above the condensation point. Accordingly, both qualitative and quantitative information regarding the levels and type of contamination are capable by utilizing the selectively coated sensors  10   b  in combination with temperature and frequency control devices. 
     As further detailed in FIG. 4 the signal produced by the SAW sensors  10   a  and  10   b  each independently pass through a high frequency amplifier  70  so as to distinguish the signal from that of any noise produced from surrounding circuitry. This results in a cleaner signal. The signal outputs  72  of the various sensors  10  are passed through a mixer  74  commonly used in the art to produce an intermediate frequency signal (not shown) so that they may be read by a low frequency counter  76  for processing by the onsite sensor interface  16 . 
     Turning now to FIG. 5 there is illustrated a flow diagram of the utilization of the electronic data produced by the sensors in the sensing and reporting of a chemical leak. The procedure can be divided into a Sensing Process  80  and a Processing and Notification Process  82 . The sensing process  80  utilizes an oscillator circuit  84  for setting the operating frequency of the sensors. A temperature compensator  86  maintains the sensors at a constant temperature so as to minimize any effects the surrounding temperature may have on the frequency of the acoustic wave. This in turn allows the SAW sensor to be more effective in detecting the rate of change in concentration of chemical vapors. The IDTs  66  are utilized to launch a surface acoustic wave across the surface of the SAW sensors arranged in the sensor array  88  at a frequency initiated by the oscillator circuit  84 . Any change in the frequency resulting from the attachment of a vapor-phase chemical to the specially coated SAW sensors described in referencing FIG. 4 is registered by the frequency counter  76 . 
     The sensor interface  16  is utilized to process the data registered by the frequency counter  76  in the Processing and Notification Process  82 . The sensor interface  16  may be a computer microprocessor commonly utilized in the art for compiling and processing data in electronic form. The computer microprocessor is utilized in conjunction with embedded software  89  to compile data  90  registered by the frequency counter  76 . The data is packaged  92  and processed  94  by the embedded software. The data is then transmitted to the remote monitoring station by means of a communication device  96  which may be a modem or other similar data transmission device commonly utilized in the art. The sensor interface  16  maintains its own operating system and logic software to control and record information from the sensors. The purpose of processing the data on site by means of the sensor interface  16  is to be able to compress and arrange the data in such a manner so as to facilitate the rapid and efficient transmission of the data to the remote monitoring station. The raw data is of such a size that to transmit it to the remote monitoring station without onsite processing by the sensor interface would be ineffective and time consuming. Additionally, the software utilized by the sensor interface  16  allows the sensor interface to recognize a pollution event by the rapid change in concentration of the VOCs detected by the sensors  10 , so that such an event may be immediately and automatically reported to the remote monitoring station  18 . 
     Referring now to FIG. 6, there is shown a flow diagram illustrating the steps involved in the software utilized by the computer processor of the sensor interface  16 . The software enables the data collection  100 , wherein the sensors  10  are polled  102  by the processor. The data retrieved from the sensors is read  104  and saved in a register  106 . Any change in the registered frequency is monitored  108 . If no change is detected, the resulting report is transmitted  110  to the remote monitoring station. If a change in frequency is detected, signifying a change in vapor concentration, the sensors registering the change in frequency are flagged  112 , and a confirmation of the frequency change is initiated  114 . This confirmation involves the accelerated polling and reporting  116  of the affected sensors, such that a result report  118  is transmitted to the remote monitoring station of a pollution event. 
     While the invention has been described herein with reference to certain preferred embodiments, these embodiments have been presented by way of example only, and not to limit the scope of the invention. Accordingly, the scope of the invention should be identified only in accordance with the claims that follow.