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Intelligent monitoring of toxic gases for the construction workers in mining (1)

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  • 1. INTERNATIONAL JOURNAL OF ELECTRONICS AND International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEMECOMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)ISSN 0976 – 6464(Print)ISSN 0976 – 6472(Online)Volume 4, Issue 1, January- February (2013), pp. 282-293 IJECET© IAEME: www.iaeme.com/ijecet.aspJournal Impact Factor (2012): 3.5930 (Calculated by GISI) ©IAEMEwww.jifactor.com INTELLIGENT MONITORING OF TOXIC GASES FOR THE CONSTRUCTION WORKERS IN MINING A.Sundaravadivelan (M.E), R.Vishnupriya M.E, R.Boopathi M.Tech, K.Sathish(M.E) V.R.S.College of Engineering & Technology, Arasur ABSTRACT The wearable computing and treatment system are used to protect the construction workers from toxic gases such as carbon-mono oxide (CO) and methane (CH4) poisoning. These poisoning are significant problem for construction workers employed in gold mining and gold cyanidation. A pulse oximetry sensor has been integrated into a typical prototype to allow continuous and non-invasive monitoring of workers blood gas saturation levels. These sensor systems monitor the condition of the workers automatically by sensing CO and CH4 level of the environment around the workplace and as well as individual heart beat of the worker. The sensor output is signal conditioned and it is digitized by using an analog to digital converter. The Microcontroller controls the operation of the ADC and the digital output of the ADC is transferred to the input port of the microcontroller. Then the transmitter section transmits that digital output to the receiver section. When the CO content of the environment goes above a threshold level the microcontroller automatically turns ON the Buzzer to indicate the critical condition. In the receiver section will be having GSM Modem to send the condition that presents in the workplace to the supervisor. Index Terms- Toxic gases, CO, CH4, Helmet prototype 1. INTRODUCTION This technique presents and prevents the workers from toxic gas poisoning, when they are employed in mining. This danger exists because the exhaust from mine- powered hand tools can quickly build up in enclosed spaces and easily overcome not only the tool’s user but co-workers as well. While the dangers of these toxicants are known, current safety systems for construction workers can only monitor the environmental concentrations. This is insufficient because toxic exposure affects people at different rates based on their activity level, body size and more significantly, their background risk factors such as smoking, anemia or prior exposure on the job site. 282
  • 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME Cyanide is a toxic substance which contains a group of chemicals containing carbonand nitrogen. These compounds are included by natural occurrence and human-madeactivities. This cyanide is used in mining to extract gold from ores, particularly low-gradeores and ores that cannot be readily treated through simple physical processes such ascrushing and gravity separation. Carbon mono-oxide is evolved during mining process, which is a colorless, odorlessgas which competes directly with oxygen in binding with hemoglobin. It is also a toxicsubstance; it affects the human blood gas saturation level. To monitor the workers for thepresence of carbon mono-oxide, Pulse oximeter is used to non-invasively measurehemoglobin concentrations within the body. Pulse oximetry is an approximation of Beer’slaw which relates attenuation of light through a medium based upon the compounds itpasses through. Methane is an odorless, colorless gas or a liquid in its cryogenic form. Both the liquidand the gas pose a serious fire hazard when accidently released. The liquid will rapidly boil tothe gas at standard temperatures and pressures. As a gas, it will act as a simple Asphyxiantand present a significant health hazard by displacing the oxygen in the atmosphere. The gas islighter than air and may spread long distances. Distant ignition and flashback are possible. Itis widely distributed in nature and the atmosphere naturally contains 0.00022 percent byvolume (2.2 ppm) Zigbee is a specification for a suite of high level communication protocols usingsmall, low-power digital radios based on the IEEE 802.15.4 -2003 standard for wirelesspersonal area networks(WPANs), such as wireless headphones connecting with cell phonevia short –range radio. The MRF24J40MA is a 2.4 GHz IEEE Std compliant, surface mountmodule compatible with microchip’s Zigbee , MiWi and MiWi P2P software stacks. The Microcontroller P89V51RD2 is a low-power, high-performance CMOS 8-bitmicrocontroller with 8K bytes of in-system programmable Flash memory. A key feature is itcan operate in X-2 mode. The on-chip Flash allows the program memory to be re-programmed in-system or by a conventional non-volatile memory programmer. P89V51RD2has the following features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, watchdogtimer, two data pointers, three 16-bit timer/counters, a six vector two-level interruptarchitecture, a full duplex serial port, on-chip oscillator and clock circuitry. Global system for mobile communication (GSM) is a globally accepted standard fordigital cellular communication. It is a Pan-European mobile cellular radio system operating at900 MHz. A switched-on mobile station with a SIM module attached. This can be used tosend short message (SMS) to different user.2. OVERVIEW The implemented technique in the past includes only Infrared (IR) imaging. It is thebest method for detecting leaks of pollutant gases, but current technology based on cooled IRimagers which is expensive ($75,000 to $150,000) for field used to meet the need ofregulatory limits—electric and petrochemical utilities, manufacturing plants and businessessuch as supermarkets. Agiltron has demonstrated a new class of IR imager instrument for thedetection of leaks of pollutant gases. Variants of the camera will be demonstrated for thelong-wave (8-12 µm) and mid-wave (3-5 µm) IR, which will be able to locate leaks fordozens of pollutant gases. The proposed technology combines Agiltron Light 283
  • 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEMELever photomechanical thermal imager technology with a tunable IR filter developedoriginally for the telecommunications industry. Agiltron is implemented by the feasibility ofthe long-wave version using sulfur hexafluoride as a target gas. The mid-wave version will beable to visualize leaks for methane, benzene and volatile organic compounds (VOCs). The proposed method to overcome the drawbacks of implemented techniquesprovides a feasibility study of a wearable computing system to protect construction workersfrom carbon mono-oxide poisoning. A pulse oximeter sensor has been integrated into atypical construction helmet to allow continuous and non-invasive monitoring of workersblood saturation levels. To show the feasibility of monitoring for carbon monoxide poisoningwithout subjecting the users to dangerous conditions as such a prototype for monitoring bloodO2 constructed and tested during a user study involving typical construction tasks todetermine its reliability while undergoing motion. Because monitoring for blood O2 and CH4involve the same principles and technologies, if monitoring O2 is feasible, then monitoringfor CH4 will be feasible as well. The results of integrating an oximeter into a construction-helmet will warn the user of impending carbon monoxide poisoning with a probability greaterthan 99%.3. BACKGROUND WORK Designing a wearable medical device for the construction workers involves a highlyinterdisciplinary approach involving human physiology, uptake of simulation, wearablecomputing and reliability analysis. Providing the history and background for each subject isunnecessary as each subject is much larger than the other methods required in this project. Fig.1. Transmitter section prototype In fig.1, the transmitter section contains the Controller, Sensors, Zigbee module andpower supply unit. These circuits are compatible and enclosed in a protective helmet. Thehelmet serves both physical protection and also protection from toxic gases. When a toxic gasis evolved, it is detected by the gas sensors. In mining, cyanide, carbon mono-oxide andmethane gases are evolved. This toxicity is detected by the respective sensors. Each andevery sensor has its threshold value. The values are measured in ppm. 284
  • 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME In fig.2, the receiver section contains the Zigbee module, relay circuit, PC system andGSM modem. It receives the information from transmitter section and drive the relay circuitto rescue the mining workers. PC system is used to note the blood gas level of the individualworkers and if the threshold level may reach or goes above the threshold level. It sends theindication to the supervisor, wherever they localized. In order for an oximeter to function,light emitted from the LED must be able to pass through the vascular tissue and back to thePD. This can either be accomplished by transmitting light directly through the tissue to thePD, or by having the light reflect off a surface within the body and return to the PD. Thesetwo types of configurations are known as transmission and reflective oximeter. While theconfiguration of the LED and PD are different, they are functionally the same..Transmissionpulse oximeter place the LED and PD on opposing sides of the tissue and measure theamount of light that passes through the area. To achieve this result, the area of interest mustbe relatively thin, such as the ear lobe, or fingertip. Reflective oximeter positions the LEDand PD on the same side of the skin and measure the light that is reflected back to thedetector. This design can be placed in a greater number of locations, including the forehead,jaw and finger. Fig.2. Receiver section prototype3.1. Prototype Design3.1.1. Carbon Mono-Oxide Sensor and Its Related Work The CO uptake model developed by Coburn, Forester, and Kane relates exogenousCO exposure and endogenous CO production, along with relevant physiological parametersto estimate the amount of CO bound with hemoglobin (COHb). This model is known as theCFK equation and has been extensively verified in several studies and renders an accurateassessment of CO uptake for various exposure levels, body sizes, and activity levels. The CFK equation treats the human physiology as a two compartment system inwhich exogenous and endogenous concentrations of carbon monoxide are exchanged bypassing through the lungs. In a steady-state exposure environment, a person will graduallyinhale and absorb carbon monoxide, producing carboxyhemoglobin, until equilibrium withthe outside environment has been produced. Because carbon monoxide diffuses equally inboth directions, a person with a high internal concentration of COHb will naturally exhale the 285
  • 5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEMEtoxin if placed in an oxygen environment the two compartmental models, combined withphysiological parameters for respiration rate, and blood stores, are the basis of the CFKequation. The form given by Tikusis d [COHb] VCO = + 1 ( PICO − [COHb]PCO 2 _____ (3.1) dt VB VBB [ HbO 2]M Additionally, exists because CO binds with hemoglobin (Hb) in place of oxygen,decreasing the amount of HbO2 in the presence of COHb. [ HbO 2] = 1.38[ Hb] − [COHb] ______ (3.2) While there are many parameters involving the CFK equation, many are eitherenvironmental or physiological constants that do not vary often. The complete table ofparameters is shown below in. We will briefly distinguish between environmental parameters(PICO, PL, PH2O) of which only PICO changes rapidly; physiological constants (DL, M,PCO2, Vco) which remain stable; and physiological variables (VB, VA, [HbO2], [COHb])which along with PICO are active in the determination of COHb levels. Vco = endogenous CO production VB = blood volume (mL) M = CO affinity for hemoglobin PCO2 = capillary pressure of O2 (mmHg) PICO = inspired pressure of CO (mmHg) PB = barometric pressure (mmHg) VA = alveolar ventilation rate PH2O = vapor pressure of water (mmHg) [COHb] = CO concentration (g/mL) [HbO2]=O2 concentration (g/mL) DL = lung diffusivity (mL/ (min*mmHg)) Beyond having a large number of parameters to estimate, implementations andpublications about the CFK equation suffer from differences between unit systems andtranslation of environmental factors between disciplines. Of critical importance is whether thevalues used in the solution come from Standard Temperature, Pressure Dry (STPD) or BodyTemperature, Pressure Saturated (BTPS) systems. The main difference between the systemsis whether water vapor is considered present in the lungs and at what temperature theexchange takes place. The original work by Coburn et al. used STPD, later validations byPeterson et al used BTPS and Bernard et al. returned to STPD. Where CFK uses the partialpressure of CO, PICO, the more common industry standard for toxins and pollutants arenoted in parts per million (ppm). The proper relationship between PICO and ppm is shownbelow. PI = ppmCO ( PB − PB − PH O ) CO 2 _______ (3.3) 106 286
  • 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME Another difficulty in understanding CFK equation is that the final result, [COHb], is notthe commonly used values of % COHB saturation. To convert from concentration in blood, topercentage saturation in blood use equation below 100*[COHb] ______ (3.4) %COHbSaturation = 1.38*[ Hb]3.1.2. Solutions to CFK Complexity is added to solving the CFK equation because [HbO2] is not constant butdependent on the current amount of [COHb] as defined in (3.2), thus the equation becomesnon-linear and must be solved through numerical means. This relationship is a key point andis easy to miss when attempting a direct solution. To compensate for this non-linearity,Peterson et al. used a trial and error method to converge on the proper value of [COHb],whereas numerical integration with RK4 was used by Bernard et al with a small enough stepsize such that (3.2) could be updated at each step. Both methods were implemented in thiswork and little difference was noted between the two solutions. With RK4 a more commonlyknown and accepted method, it will be our used for our analysis. During simulation a stepsize of 0.01 minutes was used.3.1.3. Methane Sensor MQ-5 semiconductor Sensor is used for Combustible Gas. Sensitive material of MQ-5gas sensor is SnO2, which with lower conductivity in clean air. When the target combustiblegas exist, the sensors conductivity is higher along with the gas concentration rising. Convertchange of conductivity to correspond output signal of gas concentration. MQ-5 gas sensor hashigh sensitivity to Methane, Propane and Butane, and could be used to detect both Methaneand Propane. The sensor could be used to detect different combustible gas especiallyMethane, it is with low cost and suitable for different application. The concentration of thissensor is 300-10000 ppm (parts per million). The sensing resistance (Rs) of this sensor is2K -20K (in 2000ppm C3H8). High concentrations of this gas can cause an oxygen deficient environment.Individuals breathing such an atmosphere may experience symptoms which includeheadaches, ringing in ears, dizziness, drowsiness, unconsciousness, nausea, vomiting, anddepression of all the senses. Under some circumstances of overexposure, death may occur.By using this technique we can detect the toxicity of this methane gas and also indicate, if thegas concentration goes above threshold level.3.1.4. Transmission and Reflective Oximeters To monitor workers for the presence of carbon monoxide, pulse oximetry is used tonon-invasively measure hemoglobin concentrations in the blood stream. Pulse oximetry is anapplication of Beer’s Law, which relates the attenuation of light through a medium dependentupon the compounds it passes through. In the case of pulse oximetry, as light passes throughvascular tissue, it is absorbed at different rates and frequencies for each species ofhemoglobin. The oximeter consists of a set of light emitting diodes (LEDs) of differentwavelengths and a photo detector (PD). The LED and PD orientations can be eithertransmissive or reflective. For a transmissive design, light shines through the tissue and isreceived on the other side by the PD. In a reflective design, light reflects off a surface withinthe body, such as bone, and returns to the PD. While the most common application in 287
  • 7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEMEhospitals uses a transmissive oximeter, shining through the finger, the usability constraints ofthe construction site have led us to choose a reflective sensor on the forehead. The pulse oximeter is used to create a photoplethysmograph (PPG) showing thevolumetric changes of blood through the monitoring site. The PPG value rises and falls as theheart pumps blood through the body with each peak in the signal indicating a hear beat. Atypical PPG signal is shown in a person’s hemoglobin concentration is found by comparingthe relative values of the maximum and minimum points of the PPG signal for eachfrequency of light. However, errors in calculating the concentration can occur when theperson moves, because the blood volume at the measurement site will change due to themotion rather than the heartbeat, these motions induced errors we term as motion artifacts. Equivalence of SpCO and SpO2 Oximeters: For each hemoglobin concentration ofinterest, a unique wavelength LED is required. Typically, in determination of blood oxygensaturation (SpO2), two LEDs are required. For blood carbon monoxide saturation (SpCO), upto seven LEDs are required to distinguish between carboxyhemoglobin and lesserdysfunctional hemoglobin’s. However, the difference between the two sensing technologiesis simply the number of LEDs employed. A key assumption in this feasibility study of determining how the pulse oximeterwould respond in the presence of carbon monoxide without having to subject participants todangerous environments. As described in the previous paragraphs, SpCO and SpO2 sensorsare both based on the principles of Beer’s Law and are of similar construction; they simplydiffer in the wavelengths of light used, i.e., in the number of LEDs employed. Both SpCOand SpO2 sensors are susceptible to the same motion artifacts. Thus we can use a SpO2sensor to understand how the technology performs during construction tasks, without havingto expose subjects to carbon monoxide. Consequently, if SpO2 oximeter are reliable inconstruction environments, then by their equivalent construction.3.1.5. Zigbee Module There are many wireless monitoring and control applications in industrial and homeenvironments which require longer battery life, lower data rates and less complexity thanthose from existing standards. For such wireless applications, a new standard called IEEE802.15.4 has been developed by IEEE. The new standard is also called ZigBee. The goalIEEE had when they specified the IEEE 802.15.4 standard was to provide a standard forultra-low complexity, ultra-low cost, ultra-low power consumption and low data rate wirelessconnectivity among in-expensive devices. The raw data rate will be high enough (maximumof 250 kb/s) for applications like sensors, alarms and toys Zigbee is expected to provide low cost and low power connectivity for equipment thatneeds battery life as long as several months to several years but does not require data transferrates as high as those enabled by Bluetooth. In addition, Zigbee can be implemented in meshnetworks larger than is possible with Bluetooth. Zigbee compliant wireless devices areexpected to transmit 20-400 meters, depending on the RF environment and the power outputconsumption required for a given application, and will operate in the unlicensed RFworldwide (2.4GHz global, 915MHz Americas or 868 MHz Europe). The data rate is 250kbps at 2.4GHz, 40kbps at 915MHz and 20kbps at 868MHz. IEEEand Zigbee Alliance have been working closely to specify the entire protocol stack. IEEE802.15.4 focuses on the specification of the lower two layers of the protocol (physical anddata link layer). 288
  • 8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME On the other hand, Zigbee Alliance aims to provide the upper layers of the protocolstack (from network to the application layer) for interoperable data networking, securityservices and a range of wireless home and building control solutions, provide interoperabilitycompliance testing, marketing of the standard, advanced engineering for the evolution of thestandard. This will assure consumers to buy products from different manufacturers withconfidence that the products will work together. The zigbee is used here for transmitting and receiving the information about theindividual blood gas level and as well as environmental toxic gas level. One transceivermodule is in transmitter section and another transceiver is in receiver section. The sensorsection is attached with this zigbee module for transferring information and other side forreception.3.1.6. Relay Driver The ULN2803A is a monolithic high-voltage, high-current Darlington transistorarray. The device consists of eight NPN Darlington pairs that feature high-voltage outputswith common-cathode clamp diodes for switching inductive loads. The collector -currentrating of each Darlington pair is 500 mA. The Darlington pairs may be paralleled for highercurrent capability. Applications include relay drivers, hammer drivers, lamp drivers, display drivers(LED and gas discharge), line drivers, and logic buffers. The ULN2803A has a 2.7-kW seriesbase resistor for each Darlington pair for operation directly with TTL or 5-V CMOS devices.The ULN2803A is offered in a standard 18-pin dual in-line (N) package. The device ischaracterized for operation over the temperature range of –20°C to 85°C. Fig.3. Voltage waveform The relay driver is used to drive different devices. In which we can connect 8 devicesto control them. It is for boosting the current for the device and drive smoothly withoutaffecting the system. It is placed on the receiver section to control motor and the exhaustdevices.3.1.7. Communication & Power The main connection point in the design is the break out board which holds theZigbee module. It allows direct access to the Zigbee pins and provides a regulator that stepsdown the 9V battery output to 3.3V which supplies operating power for both the Zigbee andthe its components. The primary reason for using the Zigbee is simplicity. In its most basicconfiguration the device acts as a UART replacement, transmitting over the radio items itreceives via UART and sending across its UART the packets received on the radio. 289
  • 9. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME In this manner, the Xpod can easily be made into a wireless device by connecting itsoutput line directly to the Zigbee. The measurements from the Xpod are transmitted 75 timesa second at 9600 baud to the Zigbee where it is broadcast to another Zigbee base station. Thisbase station is connected to a laptop via USB virtual serial port, from which the native NoninOximeter software can read the Xpods measurements and run without modification. While indoor ranges of 30 meters are listed for the Zigbee modules, in clutteredenvironment these ranges were not possible unless a higher-gain antenna was used at the basestation. Initially the whip" type antenna used on the helmet was at both locations. Howeverin this configuration data was dropped after only 5 meters. Replacing the whip antenna on thebase station with the UF.L type antenna resolved the problem with only a handful of packetbeing dropped.3.2. Helmet Prototype The prototype consists of Microcontroller, Single channel ADC, CO sensor andBuzzer. It is shown in fig.3.The prototype detects the carbon monoxide gas, which exhibits athreshold level of 200 ppm and it is a user defined value. An average worker, (i.e. normalhuman) having a good health can withstand 8 hour of 8.7 ppm and 8 min of 87 ppm. Becausetoday’s world wide workers were addicted to irregular activities such as smoking, drinkingetc. So it will affect the worker as quickly as possible. Thus provided range depends on theindividual workers health. Fig.4. Transmitter prototype Fig.5. Receiver prototype 290
  • 10. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME The final prototype is shown in Figure 4, with the interior view showing the attachedXpod and sensor integrated into the headband. The back view shows the Xpod connection to theXbee and required 9V battery. The following sections describe the design implications that leadto the prototypes final form. In general, the design process was driven by a desire to shape theinternal headband such that it minimized motion artifacts, and to place the electronics to reducethe impact of their weight. a)Interior view b)Back view Fig.6.Interior and Back view of prototype3.3. Head Band Design The headband insert shown in Figure 4 was not the final form factor selected for the userstudy. An earlier design did not have the sensor surrounded by the foam insert, causing the sensorto easily slip out of place when the helmet was removed. The current design is a vinyl front witha foam backing that attaches to the natural helmet headband by Velcro. The sensor is recessedinto the headband such that it is pressed against the forehead, but the extra foam padding softensthe design and provides even pressure across the forehead.3.3.1. Time to Impairment and Incapacitation A carboxyhemoglobin saturation at 30% results in confusion and impairment, whereas at60% a person would become unconscious and eventually die if not rescued. Our approach issimilar to that of Alari and Bernard and Duker who used the CFK equation to model escapetimes from fires. Also, Tikuisis compared theoretical and measured values of COHB for restingand exercising subjects. The two worker profiles were estimated at the activity levels shown inTable. The results of the estimation are shown in Table and Figure 3.2 provides a graphicalrepresentation for the uptake curves. Table 3.1: Time to Impairment (30% COHb) and Incapacitation (60% COHb) in Minutes at1200 ppm Viewing Table 3.1, the impact of higher activity levels and lower red blood cell counts isrevealed by the faster times to impairment and incapacitation. Returning to the definitions ofworst-case time to impairment (Ti), 291
  • 11. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME Table 3.1 provides these values. As would be expected, the worst-case overall is theworker that is both anemic and performing intense activity. For this particular workerTi=11.6. It is these bounds at which the prototype will be tested against to determine if itsufficiently covers the worker population. Fig.7. Carbon Monoxide Uptake at 1200ppm4. CONCLUSION A pulse oximeter has been integrated into a typical construction helmet to assess thefeasibility of monitoring for exposure to carbon monoxide and the sensor system alsointegrated into this helmet, which is in transmitter side for monitoring the workers. Duringthe observation, continuous measurements of the workers were recorded to determine howthe prototype performed under motion. The measurement gap is the time between toxic gases is inhaled by the worker and theresponse is send to the control unit. As the worker performed the activities, measurementgaps were created by periods of high motion when the oximeter could not determine a validreading. The distribution of these gaps was compared to worst-case estimate of time toimpairment for construction workers to determine if the measurement gaps were so frequentthat a worker becoming impaired would go unnoticed. This was shown not to be case as aworst case as the helmet would provide a reading in 99.66% of cases. For further assurance,the time to impairment could be halved, with the helmet still providing a reading in 99.03%cases. These designs can also incorporate a multi-modal alert that warns co-workers of aperson in danger. This alert could include transmitting radio messages and warnings tosummon distant help, or provide visual and audible clues to the location of the worker. Theseadditions would not be a large extension as wireless capability is already integrated into theprototype and could be easily turned on in case of emergencies. While these results do not ensure absolute monitoring of workers, the time toimpairment is very conservative and was derived for a very susceptible worker under verydifficult conditions. Therefore, the high probability of measurement at more than 99%indicates that helmet-based monitoring is a feasible safety platform worthy of furtherenhancement. 292
  • 12. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME5. FUTURE WORK The most compelling area for further work is in advancing the design of the helmetinsert and reducing the impact of motion. At present, the insert is made of simple materialsand Velcro is used for attachment, however a more elegant solution should be found.Additionally, a new helmet design should be attempted that mechanically isolates the innerheadband from the exterior protective shell. Because a headband design itself would sufferlittle motion artifacts, isolating the weight of the exterior helmet from sensor themselvesshould provide great advancements in resistance to motion. Also, the helmet is not anindividual solution, but part of a network of sensors on the construction site. Finally, the results of this study need to be validated with a true CO-pulse oximeter.While the blood oxygen oximeter used is technologically equivalent, there is no substitutionfor direct validation of the helmet. Hopefully as time passes the SpCO monitors will be madeavailable at lower prices and smaller form factors.REFERENCES[1] S. Dorevitch, L. Forst, L. Conroy, and P. Levy, “Toxic inhalation fatalities in US construction workers, 1990 to 1999,” J. Occup. Environn. Med., vol. 44, pp. 657–662, Jul. 2002.[2] D. J. Lofgren, “Occupational carbon monoxide poisoning in the state of Washington, 1994–1999,” Appl. Occup. Environ. Hygiene, vol. 17, no. 4, pp. 286–295, 2002.[3] Preventing Carbon Monoxide Poisoning from Small Gasoline-Powered Engines and Tools, NIOSH, 1996.[4] R. Dresher, “Wearable forehead pulse oximetry: Minimization of motion and pressure artifacts,” M.S. thesis, Worcester Polytechnic Inst., Worcester, MA, 2006.[5] Nagre and Y. Mendelson, “Effects of motion artifacts on pulse oximeter readings from different facial regions,” in Proc. IEEE 31st Annu. Northeast Bioeng. Conf., Apr. 2005, pp. 220–222.[6] Design of Pulse Oximeters, J. G. Webster, Ed. New York : Taylor Francis, 1997.[7] Y. Mendelson, J. C. Kent, B. L. Yocum, and M. J. Birle, “Design and evaluation of a new reflectance pulse oximeter sensor,” Med. Instrum., vol. 22, no. 4, pp. 167–173, 1988.[8] Y. Mendelson and C. Pujary, “Measurement site and photodetector size considerations in optimizing power consumption of a wearable reflectance pulse oximeter,” in Proc. 25th Annu. Int. Conf. IEEE Eng. Med. Biol. Soc., Sep. 2003, pp. 3016–3019.[9] M. Nogawa, T. Kaiwa, and S. Takatani, “A novel hybrid reflectance pulse oximeter sensor with improved linearity and general applicability to various portions of the body,” in Proc. 20th Annu. Int. Conf. IEEEEng. Med. Biol. Soc., 1998, pp. 1858–1861. 293

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