Application of Gas Monitoring Sensors in Underground Coal Mines ...

ISSN 2249-6343 

International Journal of Computer Technology and Electronics Engineering (IJCTEE) 

Volume 3, Issue 3, June 2013 

Application of Gas Monitoring Sensors in 

Underground Coal Mines and Hazardous Areas 

A. Kumar*, T.M.G. Kingson, R.P. Verma, A. Kumar, R. Mandal, S. Dutta, S.K. Chaulya and G.M. Prasad 

CSIR-Central Institute of Mining and Fuel Research, Dhanbad, India 

*Corresponding Author, Email: eranishkumar@gmail.com 

Abstract-Underground mining requires equipment and 

manpower to operate under the earth surface. Subsurface 

atmosphere may be contaminated with poisonous gases that 

displace the necessary oxygen to support life or flammable gases 

that may cause explosion. Therefore, it is necessary to develop 

technologies and find ways to accurately measure concentration 

levels of toxic and flammable gases levels in subsurface 

atmosphere for safety of underground coal mines. Each sensor 

has its own advantages and constraints, like some sensors are 

better for sensing toxic gases and some are better for 

combustible gas detection. The paper enumerates operating 

principle, working procedure and application of different types 

of sensors for monitoring toxic and flammable gases in 

hazardous areas. 

Index Terms- Gas sensors, MEMS, Nanotechnology, TLVs 

I. INTRODUCTION 

Underground coal mine is characterized by tough working 

condition and hazardous environment. Many accidents occur 

in underground coal mine which leads to fatal accidents and 

huge loss of properties. These accidents have variety of 

causes, including sudden rise in toxicants such as carbon 

monoxide (CO), dangerous flammable gases especially 

methane (CH 4 ) or firedamp and insufficient oxygen for mine 

workers to breathe. Therefore, for sustainable growth of coal 

mining industry and safety of miners, it is necessary to 

develop technologies and find ways to make mines hazard 

free [1]. 

To keep atmosphere just right in underground coal mine, 

the primary requirement is to regularly monitor the levels of 

gases, like oxygen, methane, carbon dioxide, carbon 

monoxide etc. This gives miners short and long term trending 

information in the subsurface atmosphere and allows early 

warning against explosive and toxic atmospheres at every 

place where miners normally work or travel. No mineworker 

should enter any underground work place, in particular those 

places with poor air circulation (e.g. blind headings), unless 

the air has been checked therein to ensure a safe breathable 

atmosphere free from levels of hazardous gases. 

II. HAZARDOUS AREA 

Fire, toxic atmospheric contaminant and dust or gas 

explosion are some critical hazards specifically linked to 

underground mining. It is necessary to figure out which area 

needs to be defined as hazardous area so that miners should 

be alerted in advance (Table I). 

A. Combustible Gases 

A hazardous area is defined based on three criteria, namely 

(i) depending upon type of gas, (ii) ignition temperature of 

the gas, and (iii) likelihood of gas being present in flammable 

concentrations. Flammability limit, thus defined, gives the 

proportion of combustible gases in a mixture, between which 

limits mixture is flammable. 

Lower Explosive Limit (LEL): The minimum 

concentration of gas or vapour mixed with air 

(percentage by volume, at room temperature) that will 

cause the propagation of flames when it comes in contact 

with a source of ignition. In common terminology, 

mixtures below the LEL are too lean to ignite. 

Upper Explosive Limit (UEL): The maximum 

concentration of gas or vapour mixed with air (percent 

by volume, at room temperature) that will cause the 

propagation of flames when it comes in contact with an 

ignition source. In common terminology, mixtures above 

the UEL are too rich to support combustion. 

B. Toxic Gases 

As toxic gases can cause harm in low levels over a long 

period of time (chronic exposure) or in higher concentrations 

over a short period of time (acute exposure), different 

countries have established threshold limit values (TLVs) for 

poisonous gases in order to advance worker protection by 

providing timely scientific information to occupational and 

environmental health professionals. 

TLVs of airborne substances refer to those concentrations 

within which personnel may be exposed without known 

adverse effects to their health or safety. Followings are the 

three types of TLVs: 

(i) Time Weighted Average (TWA) is the average 

concentration to which nearly all workers may be 

exposed over given hours of work shift/week without 

known adverse effects. However, many substances are 

sufficiently toxic that short-term exposures at higher 

concentrations may prove harmful or even fatal. 

(ii) Short-Term Exposure Limit (STEL) is a time-weighted 

average concentration occurring over a period of not 

more than few minutes. It is also recommended that such 

circumstances should not occur many times. 

(iii) Ceiling Limit (CL) is the concentration that should not 

be exceeded at any time. This is relevant for the most 

toxic substances or those that produce an immediate 

irritant effect. 

9

ISSN 2249-6343 



III. GAS DETECTING SENSORS 

Gas sensors detect presence of various gases within an 

area, usually as a part of safety system. Sensors give a 

proportional electrical response depending upon the 

concentration of gas to be detected. If the concentration 

exceeds threshold concentration limit, the instrument 

containing it will provide an alarm to nearby personnel, or it 

may activate other remedial actions, such as increasing the 

ventilation, switching off the power supply etc. [3]. Different 

methods for detecting above gases are given in Table II and 

their operating principles are summarized in Table III. 

Table II: Different methods of gas detection [4] 

Name 

Methods of detection 

Oxygen 

Electrochemical, paramagnetic, flame 

lamp 

Methane 

Catalytic oxidation, thermal 

conductivity, optical, acoustic, flame 

lamp 

Carbon dioxide Optical, infrared 

Carbon monoxide Electrochemical, catalytic oxidation, 

semiconductor, infra-red 

Sulphur dioxide Electrochemical, infra-red 

Nitric oxide, Electrochemical 

Nitrous oxide, 

Nitrogen dioxide 

Hydrogen Electrochemical, semiconductor 

sulphide 

Hydrogen Catalytic oxidation 

A. Catalytic Bead Sensors 

Theory: Combustible gas mixtures will not burn until they 

reach an ignition temperature. However, in the presence of 

certain chemical media, the gas will start to burn or ignite at 

lower temperatures. This phenomenon is known as a catalytic 

combustion. 

A coil of wire is coated with glass or ceramic material 

which is coated with a catalyst. The coil is electrically heated 

to a temperature that will allow it to burn (catalyze) 

combustible hydrocarbon (CHC) gas being monitored. 

Pellistors are miniature calorimeters used to measure the 

energy liberated by burning of a combustible (flammable) 

gas or vapor [6]. A pellistor consists of a coil of 

small-diameter platinum wire supported in a refractory bead 

coated with a layer of catalytic material (Fig. 1), on which the 

gas is burnt. The coil serves two purposes: firstly, it is used to 

heat the bead electrically to its operating temperature of 

around 500°C, and secondly it is used to detect changes in 

temperature produced by oxidation of flammable gas. 

Working procedure: A Catalytic bead sensor is used in 

Wheatstone bridge (Fig. 2), a circuit for measuring an 

unknown resistance by comparing it with known resistances. 

A balanced bridge has no output signal. R 1 is trim resistor that 

keeps the bridge balanced. 

Resistor value R B and trim pot R 1 are selected with 

relatively large resistance values to ensure proper function of 

the circuit. During its operation, a current is passed through 

the coil, which heats up the bead to a high temperature. The 

gas is burned when a flammable gas molecule comes into 

contact with the catalyst layer. The reaction occurs without a 

flame since the level is below the Lower Explosive Limit (or 

LEL) of the gas. However, during burning reaction, heat is 

released which increases the temperature of bead. This 

increase in temperature causes rise in electrical resistance of 

the coil. 

Fig.1: Catalytic bead [7] 

There is another bead in the circuit which is identical to the 

detector bead, but does not contain any catalyst. This bead 

will react to changes in humidity, ambient temperature etc., 

but will not react to flammable gas. All that is required is a 

comparison of the resistance of one bead against another in a 

Wheatstone bridge type circuit in order to obtain a 

meaningful signal. 

Fig. 2: A catalytic bead sensor Wheatstone bridge [8] 

Reaction: Reaction takes place on the surface of catalytic 

bead is given as 

CH 4 + 2O 2 + 8N 2 CO 2 + 2H 2 O + 8N 2 (1) 

From the above reaction, one part of methane requires ten 

parts of air for complete combustion. For a sensor to detect 

methane, the signal output will respond linearly from 0–5% 

of methane. As the concentration reaches close to 9%, the 

signal increases very rapidly & peaks at around 10% (Fig. 3). 

10

ISSN 2249-6343 



The signal starts to drop slowly as the concentration of gas 

passes approximately 20%; after 20% it drops sharply and at 

100% sensor signal is zero. 

follows: 

(i) Catalyst poisoning: Poisoning compounds cause a 

permanent reduction of the sensor sensitivity. The exact 

cause of poisoning is very difficult to identify. Tetraethyl 

lead, silicon compounds and sulphur compounds are 

among the most common poisons. 

(ii) Sensor inhibitors: Inhibitors cause a temporary loss of 

sensitivity to sensor and may be partially or totally 

recovered after a short exposure to fresh air. The most 

common inhibitors are H 2 S, chlorine, chlorinated 

hydrocarbons and halogen compounds. 

(iii) Sensor cracking: The sensor, when exposed to high 

concentration of gases, excessive heat and various 

oxidation processes that take place on the sensor surface, 

may eventually deteriorate its performance. 

Fig. 3: Sensor output vs. methane concentration [8] 

Factors affecting the operations of catalytic sensors are as 

Factors affecting the operations of catalytic sensors are as 

Table I: List of gases and their hazardous limits in underground mines [2] 

Name of gas Flammability Guideline for TLVs 

Hazards 

limits in air (%) 

Oxygen >19.5% Oxygen deficiency, may cause 

explosive mixtures with reactive gases 

Nitrogen CL = 81,000 ppm Inert 

Methane 5 to15 At 1% isolate electricity, at 2% Explosion 

remove personnel. 

Carbon dioxide TWA = 0.5%, STEL = 3.0%, CL = Promotes increased rate of respiration 

1.5% 

Carbon monoxide 12.5 to 74.5 TWA = 0.005%, STEL = 0.04%, Highly toxic; explosive 

CL = 200 ppm 

Sulphur dioxide 

TWA = 2 ppm, STEL = 5 ppm, CL 

= 10 ppm 

Very toxic; irritant to eyes throat and 

lungs 

Nitric oxide TWA = 50 ppm Oxidizes rapidly to NO 2 

Nitrous oxide TWA = 50 ppm Narcotic (laughing gas) 

Nitrogen dioxide TWA =3 ppm, CL= 5 ppm Very toxic; throat and lung irritant; 

pulmonary infections 

Hydrogen sulphide 4.3 to 45.5 TWA = 10 ppm, STEL = 15ppm, 

CL = 15ppm 

Highly toxic; irritant to eyes and 

respiratory tracts; explosive 

Hydrogen 4 to 74.2 Highly explosive 

Table III: Classification of sensors by transducer operating principle [5] 

Sl. 

No. 

Types of devices Physical change Source of signal 

1 Catalytic gas sensors 

(pellistors), thermal 

sensors 

2 Optical sensors 

(infrared, laser, optical 

fiber) 

Temperature or 

heat 

Absorbance 

Luminescence 

Refractive index 

Scattering 

Changes in resistance in wheat stone bridge 

3 Semiconductor (solid Electrical Changes in work function 

Either caused by gas itself, or due to reaction with certain indicator. 

Emission, caused by chemical reaction 

For example, caused by change in solution composition. 

Caused by particles of definite sizes present in the sample. 

11

ISSN 2249-6343 



state) gas sensors 

4 Electrochemical gas 

sensors 

(potentiometric or 

amperometric ) 

5 Piezo-electric sensors 

(quartz crystal 

microbalance) 

6 Flame ionization 

detector, photo 

ionization detector 

B. Infrared Gas Sensor 

conductivity 

Voltametric 

Mass 

Ionisation 

Theory: Gas molecules are made up of number of atoms 

bonded to one another. These interatomic bonds are similar to 

springs, connecting atoms of various masses together. This 

bonding vibrates with a fixed frequency called the natural 

frequency. When infrared radiation interacts with gas 

molecules as shown in Fig. 4, part of energy has the same 

frequency as the gas molecule‟s natural frequency and it is 

absorbed while rest of the radiation is transmitted. As the gas 

molecules absorb this radiation, the molecules gain energy 

and vibrate more vigorously. 

Fig. 4: Effect of infrared radiation on bonding of molecule 

This vibration results in temperature rise of gas molecules. 

Rise in temperature is detected by the detector. On the other 

hand, the radiation absorbed by the gas molecules at the 

particular wavelength will cause a decrease in the original 

wavelength. This radiation energy decrease can be detected 

as a signal also. 

Working of Non-Dispersive Infrared (NDIR): It is based 

on infrared absorption property of some gases which consists 

of a single IR source, a beam splitter and two detectors as 

shown in Fig. 5. One detector is used to monitor the 

characteristic hydrocarbon wavelength. The other is a 

reference that monitors an atmospheric “window” where no 

IR active gases are normally present. Infrared energy 

(2-5microns, where micron is a common unit to express 

wavelength in infrared range) is emitted from the source, 

passes through the gas cell, and is reflected back to the 

detectors. If no hydrocarbons are present within the gas 

sample, then energy reaching the detector is the same. 

However, if some combustible hydrocarbons are present, 

they will absorb some IR energy at that wavelength, thus 

reducing the amount received by the analytic detector. Gas 

concentration is determined by comparing the relative values 

between the two wavelengths (Fig. 6). This is called dual 

beam infrared detector [9]-[10]. 

Changes in current between electrodes is measured 

Changes of resonant frequency of quartz oscillator plate due to 

adsorption of a gas on its chemically modified surface 

Amount of ionization 

Fig. 5: Infrared gas sensor [11] 

It is well known that almost all CHCs absorb IR at 

approximately 3.4 μm wave length, and at this region H 2 O 

and CO 2 are not absorbed, making the system immune to 

humidity and atmospheric changes. Beer's Law describes the 

exact relationship between IR light intensity and gas 

concentration [12]: 

I = I 0 e kP (2) 

Where: 

I — the intensity of light striking the detector, 

I 0 — the measured intensity of an empty sample chamber, 

k — a system dependent constant, and 

P — the concentration of the gas to be measured. 

Fig. 6: Spectral absorbance by gases [13] 

Infrared detectors convert electromagnetic radiation 

energy or temperature changes into electrical signals. Some 

of the detectors (Fig. 7) types are: 

(i) Pyroelectric detector: Pyroelectric materials are crystals, 

such as lithium tantalite [14], which exhibit spontaneous 

polarization, or a concentrated electric charge that is 

temperature dependent. As infrared radiation strikes the 

detector surface, the change in temperature causes a 

current to flow. This current is proportional to the 

intensity of radiation. 

12

ISSN 2249-6343 



This detector exhibits good sensitivity and good 

response to a wide range of wavelengths, and does not 

require cooling of the detector. It is the most commonly 

used detector for gas monitors. 

(a) 

(b) 

to seal the chambers and the same intensity of pulsed 

infrared radiation is received by both chambers when no 

target gas is present. When a sample containing target 

gas flows through the sample cell, reduced radiation 

energy is received by the detector chamber. This causes 

temperature and pressure to drop in the detector 

chamber. The amount of temperature or pressure drop is 

in direct proportion to the gas concentration. In the case 

of linked chambers, the pressure difference between the 

two chambers causes a detectable flow, which is 

measured as a signal. In the case where a diaphragm 

separates the two chambers, a movement of the 

diaphragm causes a measurable change in capacitance. 

(iii) Photoacoustic detector: This detector is similar to luft 

detector except that the pressure change is measured by a 

condenser microphone. The sample gas is passed 

through a chamber at a preset time interval and the 

chamber is sealed with a fixed volume of sample gas 

trapped inside. A specific wavelength of infrared 

radiation is pulsed into the chamber via an infrared 

transparent window. The pulsating pressure change is 

measured by the microphone as a frequency change 

which produces the signal [16]-[17]. 

Fourier Transform Infrared (FTIR): FTIR measuring 

principle is used for multi-gas detection (Figs. 8). The 

principle of FTIR is that the gas to be analyzed is led through 

a cuvette with an IR light source at one end (i.e. sending out 

scattered IR light), and a modulator that “cuts” the infrared 

light into different wavelength. At other end of the cuvette, a 

detector is measuring the amount of IR light to pass through 

the cuvette. By data processing, Fourier Transformation 

mathematics is used to turn the measured absorption values 

into gas concentration for the analyzed gases. As the light is 

modulated into many different wavelengths, it is possible to 

analyze many different gases in the same instrument, such as 

CO, H 2 O, SO 2 , NO, HF, NH 3 etc. [18]. 

(ii) 

(c) 

Fig. 7: Different detectors used for converting into 

electrical signals: (a) Pyroelectric, (b) Luft and (c) 

Photoacoustic detector [13] 

Luft detector: A luft detector consists of two chambers, 

either linked by a micro flow sensor or divided by a 

diaphragm [15]. The chambers are sealed with a target 

gas at a low pressure. IR transparent windows are fitted 

Fig. 8: FTIR infrared spectrum [19] 

Infrared provides high accuracy, resistance to 

contamination and reliable measurements. Unlike catalytic 

bead sensor, gas sample enters and leaves the cell unchanged. 

Nothing is transformed, substituted or removed from it. As 

the IR source ages, its energy level decreases. But there is 

only one source. Therefore, the energy level reduction will 

equally affect both sensor tubes (reference and detection) and 

no imbalance is detected. 

13

ISSN 2249-6343 



There is no need of extreme temperature for detection, 

resulting in less stress on construction materials. As there is 

no combustion, corrosive combustion by-products are not 

produced. All electronics and active components are sealed 

away from the combustible gas environment. So, there is no 

inhibitor, which helps in providing improved gas response 

[20]. 

However, close coupling of electronics to IR sensor limits 

operation at high temperature. Exceeding the operational 

temperature limit can cause IR sensor drift or failure. Due to 

component precision and assembly, IR sensors have higher 

initial cost than catalytic detectors. IR sensors do not detect 

all combustible gases (e.g. hydrogen). Humidity and water 

may affect the sensor. Dust and dirt can coat the optics and 

impair sensor response. 

C. Electrochemical Sensors 

Theory: Electrochemical sensors are fuel cell-like devices 

consisting of an anode, cathode, and electrolyte. The 

components of the cell are selected such that target gas is 

allowed to diffuse into the cell, which causes chemical 

reactions and generates current. 

Working procedure: It (Fig. 9) consists of a sensing 

electrode (or working electrode) and counter electrode 

separated by a thin layer of electrolyte/catalysts. Gas that 

comes in contact with the sensor first passes through a small 

capillary-type opening and then diffuses through a 

hydrophobic barrier, and eventually reaches the electrode 

surface. This approach is adopted to allow the proper amount 

of gas to react at the sensing electrode to produce sufficient 

electrical signal while preventing the electrolyte leaking out 

of the sensor. The gas that diffuses through the barrier reacts 

at the surface of the sensing electrode involving either an 

oxidation (CO, H 2 S, NO, SO 2 etc.) or reduction (NO 2 and 

Cl 2 ) mechanism. These reactions are catalyzed by electrode 

materials specifically developed for the gas of interest [21]. 

following reactions: 

For working electrode: CO + H 2 O → CO 2 + 2H + + 2e - (3) 

For counter electrode: O 2 + 4H + + 4e - → 2H 2 O (4) 

Overall cell reaction: 2CO + O 2 → 2CO 2 (5) 

The main responsibility of the potentiostat circuit is to 

ensure that adequate current is fed to the counter electrode 

and the counter electrode can operate at its preferred 

potential. 

For a sensor requiring an external driving voltage, the 

sensing electrode potential does not remain constant due to 

the continuous electrochemical reaction taking place on the 

surface of the electrode. It causes deterioration of 

performance of the sensor over extended periods of time. To 

improve the performance of the sensor, a reference electrode 

is introduced. The reference electrode maintains the value of 

this fixed voltage at the sensing electrode. No current flows to 

or from the reference electrode. Sometimes a scrubber filter 

is installed in front of the sensor to filter out unwanted gases. 

[23]. 

Gas specific electrochemical sensors can be used to detect 

the majority of common toxic gases, namely CO, H 2 S, Cl 2 , 

SO 2 etc. in a wide variety of safety applications. They can be 

specific to a particular gas or vapour. They are typically very 

accurate. They do not get poisoned easily. 

As disadvantages, electrochemical gas sensors have a 

narrow temperature range and a short shelf life; they are 

subject to several interfering gases such as hydrogen. Sensor 

lifetime will be shortened in very dry and hot areas. 

D. Semiconductor Sensor 

Theory: These sensors (also called solid state sensor) are 

primarily used for toxic gas measurements and limited use in 

CHC gas measurement. A semi conducting material is 

applied to a non-conducting substrate between two electrodes 

(Fig. 10). 

Fig. 9: Electrochemical gas sensor [22] 

The counter electrode balances the reaction of sensing 

electrode – if the sensing electrode oxidizes the gas, then the 

counter electrode must reduce some other molecule to 

generate an equivalent current. 

Reactions: The reaction kinematics is explained by the 

Fig. 10: Schematic diagram of modern resistive 

semiconductor gas sensor [24] 

The substrate is heated to a temperature such that the gas 

being monitored can cause a reversible change in the 

conductivity of the semi-conducting material. The target gas 

interacts with the surface of the metal oxide film (generally 

through surface adsorbed oxygen ions), which results in 

14

ISSN 2249-6343 



change in charge carrier concentration of the material. 

This leads to alter the conductivity of the material. An 

n-type semiconductor is one where the majority charge 

carriers are electrons, and upon interaction with a reducing 

gas an increase in conductivity occurs. Conversely, an 

oxidizing gas serves to deplete the sensing layer of charge 

carrying electrons, resulting in a decrease in conductivity. 

Opposite effects are observed with p-type semiconductor 

material (Table IV). 

Tin oxide semiconductor is small, mechanically rugged, 

sensitive to parts per million (ppm) levels, flood-proof and 

less expensive. The major disadvantage of the sensor is that 

the sensor is sensitive to humidity and temperature, but not 

specific to gases and vapors. 

Table IV: Response of semiconductor for different types 

of gases [25] 

Classification Oxidizing gases Reducing gases 

n-type 

p-type 

Resistance 

increase 

Resistance 

decrease 

Resistance 

decrease 

Resistance 

increase 

Working procedure: The gas sensing film is located on a 

micro machined hotplate which operates at 100-400 °C. 

Under zero gas condition, it is assumed that O 2 molecules tie 

up free electrons in the metal oxide semiconductor material 

by absorbing on its surface, thereby inhibiting electrical flow 

[26]. The depleted layers are responsible for a high contact 

resistance. For conduction, electrons must cross over the 

surface barriers. 

As reducing gases (CO, methane, H 2 S or H 2 gases) are 

introduced, they replace the O 2 , release free electrons and 

decrease resistance between the electrodes (Fig. 11). This 

change in resistance is measured electrically. It is 

proportional to the concentration of gas being measured [28]. 

The sensitivity of metal-oxide gas sensors can be 

substantially improved by dispersing a low concentration of 

additives, such as Pd, Pt, Au etc. 

Reactions: Atmospheric oxygen molecules are adsorbed 

on the surface of semiconductor oxides in the form of O − , O 2- 

or O 2 − . The reaction kinematics is explained by the following 

reactions: 

O 2 (gas) + e − → O 2 (ads) − (6) 

O 2 (gas) − + e − → 2O (ads) − (7) 

The presence of chemically adsorbed oxygen causes 

electron depletion in the thin film surface and building up of 

Schottky surface barrier. Consequently, the electrical 

conductance of thin film decreases to a minimum. The SnO 2 

thin film interacts with oxygen by transferring the electron 

from the conduction band to adsorb oxygen atoms. The 

response to H 2 S can be explained as a reaction of gas with the 

O 2 (ads) − : 

H 2 S + 3O (ads) − → H 2 O(g) + SO 2 (g) + 3e − (8) 

With this reaction, many electrons are released to thin film 

surface. This decreases the Schottky surface barrier and 

makes depletion layer thinner; consequently, the electrical 

conductance of the thin film increases. Metal oxide 

semiconductor (MOS) sensors may be used for toxic as well 

as combustible gas monitoring. 

Fig.11: Conductivity model of SnO 2 : (a) in air; (b) during 

exposure to CO (Debye length lD

ISSN 2249-6343 



sensor. 

Working procedure: Most of gaseous materials show 

characteristic optical absorptions, especially in the 

mid-infrared (2–25µm) band. The optical fingerprints of 

different gases have made the spectral absorption a unique 

method of gas analysis [31]. In TDLAS, a diode laser emits 

light at a well-defined but tunable wavelength over the 

characteristic absorption lines of a target gas in the path of the 

laser beam. This causes a reduction of the measured signal 

intensity, which can be detected by a photodiode, and then 

used to determine the gas concentration (Fig. 12). 

Fig. 12: TDLAS gas detector system [32] 

Different diode laser are used based on application and the 

range of tuning required. Typical examples of laser diode are 

InGaAsP/ InP (tunable over 900 nm to 1.6 µm), InGaAsP/ 

InAsP (tunable over 1.6 µm to 2.2 µm) [33]. Varying the 

quantum cascade laser (QCL) temperature and/or laser 

injection current provides wavelength tuning of the emitted 

laser radiation from DFB devices within a limited spectral 

range (~10 cm-1). The external cavity configuration, 

EC-QCL approach allows tuning over a range of >200 cm-1 

[34]. Wavelength modulation spectroscopy (WMS) is based 

on the modulation of the light emitted by a laser that is slowly 

tuned through an absorption feature of the species to be 

detected. The signal of second harmonic can be measured 

with lock-in amplifier and it is proportional to the 

concentration [35]. In different temperature conditions, for 

the same concentration of gas, the amplitude of second 

harmonic detected by lock in amplifier fluctuates with the 

variation of ambient temperature. WMS measures faster 

response and can provide parts per million (ppm) to parts per 

billion (ppb) chemical detection limits, depending on the 

spectroscopic properties of the target gas and the sampling 

path length. WMS is thus a highly sensitive and gas-specific 

form of spectroscopic gas analysis [32]. 

Advantages: 

a. TDLAS has been widely employed in detecting 

atmospheric trace gases due to its high sensitivity, high 

selectivity, and fast time. 

b. TDLAS method uses a compact single mode diode laser 

tuning over an interested wavelength range swiftly to 

fulfill the function of spectroscopy scan, may overcome 

the drawback of FTIR, especially in field on-line 

applications where fast response needed [29]. 

c. A further advantage of near infrared TDLAS is 

compatible with optical fibers for optical 

communication, which makes it easy to realize 

multipoint remote sensing. 

d. The laser emission line-width is narrower than gas 

absorption line-widths. This may be contrasted with 

near-IR (NIR) absorption techniques that sample with 

broadband sources and measure absorption from 

multiple lines across a fairly broad range of frequencies. 

TDLAS thus offers the advantage of selectivity for a 

target trace gas absent spectral interferences from other 

background gases. 

Disadvantages: 

a. In different temperature conditions, for the same 

concentration of gas, the amplitude of second harmonic 

detected by lock in amplifier fluctuates with the variation 

of ambient temperature. For the retrieval of the trace gas 

concentration, the influence of temperature fluctuations 

must be taken into account. 

b. Any noise introduced by the light source or the optical 

system will deteriorate the detectability of the technique. 

2) Differential Absorption Light Detection and Ranging 

Theory: Simple TDLAS measures the presence/ 

concentration of a particular gas is based on receiver 

measuring wavelength not absorbed by the target gas 

whereas differential absorption light detection and ranging is 

based on returning backscattered signal intensity absorbed by 

target gas as shown in Fig. 13. This system can detect and 

measure the presence of CO 2 , CO, CH 4 etc. LIDAR (Light 

Detection And Ranging) operates in the ultraviolet, visible 

and infrared portion of the spectrum [36]. 

Fig. 13: Differential absorption LIDAR concept [36] 

Working procedure: The laser source emits a laser beam in 

tune with molecular absorption line of a target gas and 

receives a reflected signal affected by gas absorption of the 

target gas in the atmosphere [37]. Near the optimum 

wavelength for the particular gas to be measured, the amount 

of absorption of the transmitted light varies strongly 

according to the wavelength for each particular molecule, and 

this creates unique molecular “signatures” for these gases. 

Therefore, the method called “Differential Absorption 

LIDAR” (DIAL) can be used to determine the concentration. 

16

ISSN 2249-6343 



The large dust particles also backscatter radiation, but their 

scattering is much less wavelength dependent [38]. 

F. Fiber Optic Sensor 

Theory: Two distinct approaches used in fiber optic 

sensors are: Firstly, by directly probing the spectrochemical 

changes, when interrogating wavelength coincides with the 

absorption band of the analyte. Such direct spectroscopic 

measurement is observed in near infrared TDLAS. Secondly, 

by utilizing an analyte specific reagent transducer converts 

analyte concentration into an optical signal. Majority of this 

involve an intermediate sensor element, which undergoes 

chemical changes initiated in the presence of the specific 

analyte [39]. 

In second method, sensor works based on modified 

cladding approach [40]. The cladding of the optical fiber is 

removed and the gas sensitive material (the conducting 

polymer film) is coated on a small section of the fiber 

(sensing probe). The sensing probe length, source intensity 

and source wavelength, indicates influence on the sensor 

response. 

Working procedure: Optical fiber sensor uses a light 

modulation, i.e. one of the light parameter changes according 

to the analytes presence. Organic conducting polymer such as 

polypyrrole, polyaniline, polythiophene shows a reversible 

change in their resistance when exposed to certain vapors 

[41]. The change in conductivity changes permittivity, which 

leads to change in the refractive index. The analytes reacts 

with the coating to change the optical properties i.e. refractive 

index, absorbance, and fluorescence which is coupled to core 

to change the transmission properties through the optical 

fiber. An extrinsic fiber-optic evanescent wave chemical 

sensor is developed by replacing a certain portion of the 

original cladding with chemically sensitive material [42]. 

The sensor structure in which small section of cladding is 

replaced with chemically sensitive layer is shown in Fig. 14. 

Advantages of fiber optic sensor are geometrical 

flexibility, remote sensing capability, small size and 

lightweight. It offers complete electrical isolation. 

G. Thermal Conductivity 

The principle of thermal conductivity is very similar to that 

of the pellistor. Two platinum coils are arranged in a 

Wheatstone bridge circuit. One coil is in contact with the gas 

stream and other is sealed into a separate chamber, used for 

temperature compensation (Fig. 15). All the gases have 

different thermal conductivity‟s and so will conduct heat 

away from the coil in the gas stream at different rates. The 

change in temperature of the coil is directly proportional to 

the change in thermal conductivity of the gas mixture flowing 

past it [43]. 

The major drawback of the sensor is that it is less selective 

and sensitive. This technique for detecting gas is suitable for 

the measurement of high (%V/V) concentrations of binary 

gas mixes 

Fig.15: Thermal conductivity [44] 

H. Ionization Detector 

Photo ionization (Fig. 16) and flame ionization (Fig. 17) 

are common detection techniques used for gas 

chromatographic (GC) systems in laboratory environments. 

Both have very good sensitivity and large linear dynamic 

range. 

Fig. 14: Configuration of fiber optic sensor and geometric 

optics ray through the sensing region [42] 

Any change in the refractive index of the modified 

cladding due to the analyte can change the condition of total 

internal reflection between the modified cladding and air, and 

results in an intensity change. 

Fig. 16: Photo ionization detector [47] 

Both techniques measure the current generated by the 

ionized species sensed by ion collector. The photoionization 

technique ionizes molecules using a high energy photon 

source, such as ultraviolet (UV) radiation [45], while flame 

17

ISSN 2249-6343 



ionization technique burns organic molecules in a hydrogen 

flame [46]. The ions generations are detected similarly in 

both PIDs and FIDs. When electric field gradient is applied 

across the ionization region to drive the ions to the electrodes, 

the ions release their charges to produce signals that can be 

processed. 

Fig. 18: CMOS based micro hotplate design of gas sensor 

array [50] 

The resistance of a metal oxide film varies depending on 

the type of gas exposure. Combustible gases such as CH 4 , 

H 2 S and NH 3 act as reducing agents thereby adding electrons 

to the metal oxide, which increases conductivity (decreases 

resistance). Metal oxide sensing films have been doped with 

noble metals to increase sensitivity and reduce response time. 

Dopants such as Pt or Pd are catalysts that promote chemical 

reactions by reducing the activation energy between the film 

and test gas without being consumed by them. This allows the 

reaction to occur at a faster rate and lower gas concentrations. 

Cantilever based sensor (piezoelectric based): 

Piezoelectric power generator made by MEMS technology 

can scavenge power from low-level ambient vibration 

sources. The developed MEMS power generators are 

featured with fixed/narrow operation frequency and power 

output in microwatt level [52]. These devices can be used as 

sensing platforms. Molecular adsorption of target gas onto 

Fig. 17: Flame ionization detector [48] 

The main differences between these two techniques are 

their ionization source and mechanism. The photoionization 

technique is a nondestructive method whereas the gas sample 

is destroyed in flame ionization method. 

I. MEMS Technology 

Micro-electro-mechanical systems (MEMS) are 

three-dimensional, electro-mechanical devices, which are 

made by micromachining silicon wafers using standard 

microelectronic fabrication and post-process techniques [49]. 

MEMS have been used to reduce the size, power 

consumption and cost of gas sensors while improving overall 

performance [50]. MEMS can be used in different innovative 

ways by combining the existing proven technologies as 

described herewith. 

MEMS based array of sensor (work function based): 

Micromachining processes have enabled designers to place 

arrays of sensors on a single chip that can be mass-produced 

at reduced cost. SnO 2 /Pt, WO 3 /Au and ZnO/Pd sensing films 

were found sensitive to the target gases NH 3 , H 2 S, and CH 4 , 

respectively. Sensing pastes are deposited on the outside of a 

ceramic tube with a heater on the inside (Fig. 18). But these 

sensors have some cross-sensitivity. Further, this technique 

suffers from baseline drift, and high resistance and recovery 

time. However, sensor array response to the gases is unique, 

which allows selectivity by pattern recognition [51]. 

Fig. 19: Cantilever based hydrogen gas sensor [54] 

the sensing element, a cantilever, shifts its resonance 

frequency and changes its surface forces (surface stress). 

Adsorption onto the sensing element (composed of two 

chemically different surfaces) produces a differential stress 

between the two surfaces and induces bending. The analyte 

that induces the mechanical response is chemisorbed onto the 

cantilever in a reversible or irreversible process. Devices that 

respond to chemical stimuli in this manner are referred as 

micro-cantilever sensors [53]. 

Cantilever based hydrogen sensor uses piezoelectric 

principle for gas sensing. This sensor uses stress-sensitive, 

palladium coated micro-cantilevers to detect hydrogen (Fig. 

19). Absorption of hydrogen into palladium is fully 

reversible, at any given moment the cantilever capacitance 

indicates the current hydrogen concentration [54]. 

J. Nanotechnology 

Applications of nanotechnology in gas sensors are still in 

the preliminary stage of development. Presently, metal oxide 

1-dimensional (1D) nanostructure as gas sensors are most 

promising area for nanotechnology. Some other 1D 

nanostructure gas sensors operation is based on changes in 

the photoluminescence spectroscopy and the mass of sensing 

18

ISSN 2249-6343 



element, which accurately uses a quartz crystal microbalance 

[55]. 

1D nanostructure has advantages over conventional 

metal-oxide-based sensors in terms of power consumption, 

sensitivity, miniaturization and large surface area to volume 

ratio [56]. The change in the electrical conductivity caused by 

chemisorption of gas molecules on the surface of 1D 

nanostructure metal oxides is measured by 

electro-transducers. The main structures of the 

electro-transducers are field effect transistors (FET), resistive 

gas micro-sensors, and resistive gas sensors [57]. 1D 

nanostructure FET is fabricated using a single nanowire 

bridge between two metal electrodes on a heavily doped 

silicon substrate covered with SiO 2 acting as insulating layer 

between the nanowire/electrode combinations and the 

conducting silicon (Fig. 20). 

Fig. 20: The schematic of the single nanowire FET [57] 

Resistive gas micro-sensors are manufactured by MEMS 

technology in which a film composed of nanowires is 

contacted by pairs of metal electrodes on a substrate (Fig. 

21). The measurement is performed by monitoring the 

changes in current or resistance of the device. The other one 

is resistive gas sensor, the channel length between the two 

electrodes for resistive sensor is usually in the millimeter 

scale within a ceramic tube. 

the sensing material. It is quantitatively measured based on 

change in frequency rate (S f ) given by: 

S f = |∆f/∆t| = | (af 2 ∆m/A)/ ∆t | (9) 

Where, 

∆ƒ — response frequency shift within the time interval of 

∆t, 

a — constant, 

ƒ— fundamental frequency of the unloaded piezoelectric 

crystal, 

∆m — mass loading on the surface of the crystal, and 

A — surface area of the electrode. 

Ceramics such as zinc oxide (ZnO), tin oxide (SnO2), 

indium oxide (In2O3), and titanium dioxide or titania (TiO2) 

are used as nanowires/nanobelts for gas sensing. Carbon 

nanotubes (CNTs) have many distinct properties that may be 

exploited to develop next generation sensors. Single walled 

nanotubes (SWNTs) have been highlighted as gas-sensing 

elements due to the 1D structure with all the atoms residing 

only on the surface. 

CNTs can be designed to have specific properties by 

changing the ratio of diameters of linearly joined CNTs, 

which in turn can be used in fabrication of FETs. The 

untreated SWNT-FET typically shows a p-type behavior, 

with threshold voltages being shifted upon gas exposure [58]. 

The inlet and outlet valves allow gases to flow over the 

carbon nanotubes of FET. Gas flow increases conductance of 

the carbon nanotubes. This can be obtained using 

current-voltage relationship before and after exposure to the 

gases. The effect occurs because when the gas molecules 

bond to the carbon nanotubes, charge is transferred from the 

nanotubes to the gas molecules, which increases 

hole-concentration in the carbon nanotubes and enhances the 

conductance (Fig. 22). The carbon nanotubes are covered 

with an insulating protection film [59]. CNTs show almost 

threefold sensitivity and efficiency compare to other metal 

oxide gas sensors available in the market, such as tin oxide 

sensor [60]. 

Fig. 21: Resistive nano-sensors: (a) MEMS structures with 

interdigitated electrode; and (b) nanowire gas sensors on 

ceramic tube [57]. 

For photoluminescence measurement, nanowire samples 

are mounted in a small vacuum chamber with ports to pass 

gasses and provide optical access. Photo-desorption and 

photo-adsorption of gases are found to affect the intensity, 

indicating the participation of free carriers. The time 

dependence of the changes in the spectral peak intensity is 

compared for measurement of gas concentration. 

Quartz crystal microbalance (QCM) is an extremely 

sensitive measurement device. The principle of measurement 

is based on mass change as the gas adsorbs on the surface of 

Fig. 22: Carbon nanotubes based gas sensor using MEMS 

platform [61] 

IV. CHARACTERISTICS OF GAS SENSORS 

Performance of sensors is characterized by the following 

parameters [62]: 

Sensitivity is a change of measured signal per analyte 

concentration unit, i.e. the slope of a calibration graph. 

19

ISSN 2249-6343 



 

 

 

 

 

 

 

 

 

 

This parameter is sometimes confused with the detection 

limit. 

Selectivity refers to characteristic that determines 

whether a sensor can respond selectively to a group of 

analytes or even specifically to a single analyte. 

Stability is the ability of a sensor to provide reproducible 

results for a certain period of time. This includes 

retaining the sensitivity, selectivity, response and 

recovery time. 

Detection limit is the lowest concentration of the analyte 

that can be detected by the sensor under given 

conditions, particularly at a given temperature. 

Dynamic range is the analyte concentration range 

between the detection limit and the highest limiting 

concentration. 

Linearity is the relative deviation of an experimentally 

determined calibration graph from an ideal straight line. 

Resolution is the lowest concentration difference that 

can be distinguished by sensor. 

Response time is the time required for sensor to respond 

to a step concentration change from zero to a certain 

concentration value. 

Recovery time is the time it takes for the sensor signal to 

return to its initial value after a step concentration 

change from a certain value to zero. 

Working temperature is usually the temperature that 

corresponds to maximum sensitivity. 

Hysteresis is the maximum difference in output when the 

value is approached with an increasing and a decreasing 

analyte concentration range. 

 

Life cycle is the period of time over which the sensor 

will continuously operate. 

V. COMPARISON OF VARIOUS SENSORS 

An ideal sensor would possess: (i) high sensitivity, 

dynamic range, selectivity and stability; (ii) low detection 

limit; (iii) good linearity; (iv) small hysteresis and response 

time; and (v) long life cycle. However, no single gas sensor is 

perfect in all the above parameters. Combination of 

appropriate detectors and sampling techniques help in 

reliable measurement of the target gas based on ambient 

conditions of the measuring area. Selection of right sensor is 

important for mitigating the impending hazard. 

One sensor can be evaluated and compared against other 

sensors. Selection of sensors depends on various parameters, 

namely physical properties of target gases, ambient 

conditions, required sensitivity, maintenance cycle, method 

of operations etc. Given the large number of variables, it is 

tempting to either oversimplify the selection process to a few 

rules. Three qualities are essentially required in a sensor for 

gas monitoring, i.e. simple, reliable and easy to maintain. 

Simple means not much complicated, adapted to user‟s 

requirement and backed by strong technology. Reliable 

indicates always “alarm” when required and “never” when 

should not. Easy to maintain specifies calibration is not 

required often, lifespan is long and troubleshooting is simple. 

Advantages and disadvantages of different types of sensor 

are summarized in Table V. 

Table V: Comparison of various gas detection techniques [63] - [65] 

Sensor Advantages Disadvantages 

Catalytic Simple, robust and inexpensive. Sensor poisoning, sensor inhibitors and sensor cracking 

Infrared 

Electrochemical 

Semiconductor 

(solid state) 

Fiber optic (clad 

modified) 

Laser 

Flame ionization 

detector 

Photo ionization 

detector 

Thermal 

Conductivity 

Immune to poisons and contamination, fail-safe 

operation, no routine calibration is required, and 

ability to operate in continuous presence of gas. 

Reliable, fast response, low power, measures toxic 

gases in relatively low concentration, and wide 

range of gases can be detected. 

Robust, long operating life, wide operating 

temperature range, detect wide range of gases. 

High sensitivity, short response time and operate at 

room-temperature. 

No interference from other gases, high speed, high 

selectivity, low maintenance and operating cost, 

and self-calibration. 

Best for CHC compounds. 

Good method for organic compound detection at 

low level. 

General applicability, large linear range, simplicity 

and non-destructive. 

Flammability detection is only in %LEL range, high to 

medium power consumption, and the gas must be infrared 

active. 

Limited to operate at low ambient temperature and narrow 

pressure range, unsuitable for use in dry atmosphere and not 

fail-safe. 

Commonly poor selectivity causing „false‟ alarm, high 

power consumption and response drift problem. 

Not stable for long time, irreversibility, and low selectivity. 

Only one gas can be measured with each instrument; heavy 

dust, steam or fog blocks laser beam. 

Not used in explosive areas, destroy the sample, responds 

poorly to halogenated hydrocarbons, and non-specific 

response. 

Non-specific response, and responds only to ionizable 

gases. 

Low sensitivity 

20

ISSN 2249-6343 



Nanotechnology 

Ultra-sensitive, large surface area to volume ratio, 

fast response time and light weight. 

Fabrication and repeatability is difficult, and expensive. 

VI. CONCLUSIONS 

Sensors help in maintaining safe and healthy environment 

in the underground mines by continuous monitoring of 

ambient air and taking appropriate control measures. Several 

promising new sensors have been developed, but no single 

sensor is reliable enough to detect every gas accurately. 

Catalytic bead sensor is simple but always not reliable and 

often calibration is required. However, IR sensor is reliable 

and easy to maintain, but it is expensive. 

When toxic gas sensors are compared, there are apparent 

design weaknesses in the semiconductor sensors as compared 

to the electrochemical sensors. The biggest drawback is 

response time. Traditional electrochemical sensors too have 

disadvantages, but new developments in electrochemical 

technology have removed many of those shortcomings. 

Among many developments, MEMS is an emerging 

technology which uses the tools and techniques that were 

developed for the integrated circuit industry to build 

microscopic sensors. These sensors are built on standard 

silicon wafers. However, one of the disadvantages of the 

traditional semiconducting metal oxide gas sensors is low gas 

sensitivity due to the limited surface-to-volume ratio. In 

addition, many of the ceramic and thin film gas sensors must 

be operated at temperatures exceeding 500 ˚C in order to 

improve the sensitivity. 

Nano-materials offer new possibility for improving solid 

state gas detection. Nanostructure sensing materials such as 

nanowires, nanotubes and quantum dots offer an inherently 

high surface area. In fact, carbon nanotubes have one of the 

best available surface-to-volume ratios. The increased 

surface area leads to high sensitivity, fast response and often 

allows lower operating temperatures. In addition, different 

types of nano-materials have different sensitivity. By 

applying different nano-materials on the same MEMS 

platform more gas mixtures can be detected. 

The future of gas sensor is determined to a great extent by 

new detection principles, new or enhanced sensors, 

sophisticated evaluation algorithms and latest 

communication technologies. Equally, new demands arising 

from unconventional applications have stimulated new 

solutions, combining proven technologies in novel and 

innovative ways. 

ACKNOWLEDGMENTS 

Authors are grateful to Dr. Amalendu Sinha, Director, 

CSIR-Central Institute of Mining and Fuel Research, 

Dhanbad for giving permission to publish the paper. 

REFERENCES 

[1] S. R. Raheem “Remote monitoring of safe and risky regions of toxic 

gases in underground mines: a preventive safety measures,” In: 

Postgraduate Diploma thesis report, African Institute for 

Mathematical Sciences (AIMS), South Africa, 2011 

http://users.aims.ac.za/~soliu/soliu.pdf. 

[2] M. J. McPherson, “Gas in subsurface opening,” In: Subsurface 

ventilation and environmental engineering, Chapter-11, 1st ed. – 

London: Chapman and Hall, pp. 11.2-11.4, 1993. 

[3] P. R. Warburton, “Methods of Identifying the Gas,” US Patent no. 

6165347, 2000. 

[4] http://www.usmra.com/download/minegases.htm 

[5] S. D. Gupta, S. Kundu, A. Mallik, “A MEMS based carbon 

nanotube–field effect transistor as a gas sensor,” International Journal 

of Recent Technology and Engineering, vol. 1, pp. 38-42, 2012. 

[6] J. B. Miller, C. Hort, T. B. Scheffler, “Catalytic sensor,” US Patent no. 

6911180 B2, 2005. 

[7] http://www.e2v.com/products-and-services/instrumentation-solutions/ 

gas-sensors/our-gas-sensor-technology/pellistors-catalytic-bead/ 

[8] http://www.intlsensor.com/pdf/catalyticbead.pdf 

[9] Diekmann, “Infrared optical sensor,” US Patent no. 6392234, 2002. 

[10] J. Y. Wong, “Intrinsically safe improved sensitivity NDIR gas sensor 

in a can”, US Patent no. 20120049071, 2012. 

[11] http://www.rkiinstruments.com/pages/faq/Catalytic_Infrared_Sensors. 

htm 

[12] C. Li and Z. Yin , “Infrared gas sensor,” In: Proceedings of the Third 

International Symposium on Electronic Commerce and Security 

Workshops, Guangzhou, China, , pp. 101-104, 29-31 July 2010. 

[13] http://www.intlsensor.com/pdf/infrared.pdf 

[14] Z. Wendong, T. Qiulin, L. Jun, X. Jijun, X. Chenyang and C. Xiujian, 

“Two-channel IR gas sensor with two detectors based on LiTaO 3 

single-crystal wafer,” Elsevier: Optics and Laser Technology, vol. 42, 

no. 8, pp. 1223-1228, 2010. 

[15] L. H. Crawley, “Application of non-dispersive infrared (NDIR) 

spectroscopy to the measurement of atmospheric trace gases,” In: 

Master of Science (Environmental Science) thesis report, University of 

Canterbury, Christchurch, New Zealand, 2008. 

[16] T. M. Rezachek , “ Photoacoustic sensor,” US Patent no. 7958771, 

2011 

[17] R. Muehleisen , “Photoacoustic sensor,” US Patent no. 20120103065, 

2012. 

[18] http://www.flsmidth.com/en-Us/Gas+Analysis+Technology/Products/ 

Measuring+Principles/FTIR 

[19] http://photometrics.net/analytical-techniques/fourier-transform-infrare 

d-ftir-spectroscopy 

[20] http://www.isa.org/InTechTemplate.cfm?Section=Measurement1&te 

mplate=/ContentManagement/ContentDisplay.cfm&ContentID=8308 

0 

[21] Davis, “Electrochemical sensor,” US Patent no. 2011010813, 2011. 

[22] http://www.nemoto.co.jp/en/column/09_ecco.html 

[23] http://www.intlsensor.com/pdf/electrochemical.pdf 

[24] http://nano.aalto.fi/en/research/groups/epg/research/gas_sensors/ 

[25] D. E. Williams, “Semiconducting oxides as gas-sensitive resistors”, 

Sensors and. Actuators B: Chemical, vol. 57, pp. 1–19, 1999. 

[26] A. Vergara and E. Llobet, “Sensor selection and chemo-sensory 

optimization: Toward an adaptable chemo-sensory system”, Frontiers 

in Neuroengineering, vol. 4, pp. 1-2, 2012. 

[27] U. Hoefer, J. Frank and M. Fleischer, “High temperature Ga 2O 3-gas 

sensors and SnO 2-gas sensors: a comparison”, Sensors and Actuators 

B: Chemical, vol. 78, no. 3, pp. 6–11, 2001. 

[28] G.L. Anderson and D.M. Hadden, “The gas monitoring handbook”, 

Avocet Press Inc., New York, pp. 59, 1999. 

[29] Y. He, Y. Zhang, R., Kan, L. Wang, K. You and J. Liu, “Study on mash 

gas monitoring with distributed multipoint fiber optic sensors system in 

coal mine”, In: Proceedings of IEEE Symposium on Photonics and 

Optoelectronics (SOPO), Shanghai, China, pp.1-4, 21-23 May 2012. 

[30] J. R. Cao and M. Miyawaki, “Gas detection and photonic crystal 

devices design using predicted spectral responses”, US Patent no. 

7352466, 2008. 

[31] Y. Zhang, G. Xu, A. Li, Y. Li, Y. , Gu, S. Liu and L. Wei , 

“Mid-infrared tunable diode laser absorption spectroscopy for gas 

sensing”, In: Proceedings of Joint 31st International Conference: 

IEEE Conference on Infrared Millimeter Waves and 14th International 

Conference on Teraherz Electronics, , Shanghai, China, 18-22 Sept. 

2006, pp. 181. 

[32] M. B. Frish, R. T. Wainner, M. C. , Laderer, B. D. Green and M. G. 

Allen, “Standoff and miniature chemical vapour detectors based on 

21

ISSN 2249-6343 



tunable diode laser absorption spectroscopy”, IEEE: Sensor, vol. 10, 

no. 3, pp.639-646, 2010. 

[33] http://en.wikipedia.org/wiki/Tunable_diode_laser_absorption_spectro 

scopy. 

[34] F. K. Tittel, Y. Bakhirkin, R. F. Curl, A. Kosterev, R. Lewicki, S. So, 

and G. Wysocki , “Quantum cascade laser based trace gas sensor 

technology: Recent advances and applications”, In: Proceedings of 

Sensors, IEEE Conference, Atlanta, pp.1334-1336, 28-31 Oct. 2007. 

[35] C. Jia-nian, Z. Ke-ke, W. Zhuo, Y. Rui, and W. Yong, “Optic fiber 

methane gas sensor based on tunable diode laser absorption 

spectroscopy”, In: Proceedings of IEEE Symposium on Photonics and 

Optoelectronic (SOPO), Chengdu, China, pp.1-5, 19-21 June 2010. 

[36] http://www.met.tamu.edu/class/metr451/Ch11folder/sld029.htm 

[37] C. R. Prasad, B. Lin and H.S. Lee, “Airborne tunable mid-IR laser 

gas-correlation sensor”, US Patent no. 7965391, 2011. 

[38] http://www.jpinnovations.com/pages/Hazardous_Gas_Detection_Syst 

em.pdf 

[39] S. J. Mechery and J. P. Singh, “Fiber optic based gas sensor with 

nanoporous structure for the selective detection of NO 2 in air samples”, 

Elsevier: Analytica Chimica Acta, vol.557, no. 1-2, pp. 123-129, 2006. 

[40] K. P. Kakde and P. D. Gaikwad, “Development of optical fiber toxic 

gas sensor using conducting polymer film”, In: Proceedings of 

International Conference on Advancements in Electronics and Power 

Engineering, Bangkok, Thailand, Planetary Scientific Research 

Center, 23-24 Dec. 2011 

[41] N. E. Agbor, M. C. Petty and A. P. Monkman, “Polyaniline thin films 

for gas sensing”, Sensors and Actuators B: Chemical, vol. 28, no. 

173-179, 1995. 

[42] J. Yuan and M. E. Sherif, “Fiber-optic chemical sensor using 

polyaniline as modified cladding material”, IEEE: Sensor, vol. 3, no. 1, 

pp. 5-12, 2003. 

[43] M. Matsuhama, T. Seko, S. Takada, H. Mizutani, T. Oida, M. Endo and 

T. Ido, “Thermal conductivity sensor”, US Patent no. 8302459, 2012. 

[44] http://www.versaperm.com/thermal_conductivity_sensor.php 

[45] W. Yang and P. C. Hsi, “Selective photo-ionization detector using ion 

mobility spectrometry”, US Patent no. 6509562B1, 2003. 

[46] M. Jorg and W. Kuipers, “Flame ionization detector”, US Patent no. 

8305086, 2012. 

[47] http://www.shsu.edu/~chm_tgc/PID/PID.html 

[48] http://www.shsu.edu/~chm_tgc/primers/FID.html 

[49] S. K. Shukla, S. Dutta, S. K. Chaulya, P. K. Mishra and G. M. Prasad, “ 

Application of MEMS sensors for landslide monitoring and detection”, 

In: Proceeding of National Seminar on Frontiers in Electronics, 

Communication, Instrumentation and Information Technology, Indian 

School of Mines(ISM), Dhanbad, pp.3-4, 2011. 

[50] P. Bhattacharyya, P. K. Basu, B. Mondal.and H. Saha, "A low power 

MEMS gas sensor based on nanocrystalline ZnO thin films for sensing 

methane”, Elsevier: Microelectronics Reliability, vol. 48, pp. 

1772-1779, 2008. 

[51] K. D. Mitzner, J. Sternhagen, D. W. Galipeau, “Development of a 

micromachined hazardous gas sensor array", Sensors and Actuators B: 

Chemical, vol. 93, pp. 92–99, 2003. 

[52] J. Q. Liu, H. B. Fang, Z. Y. Xu, X. H. Mao, X. C. Shen, D. Chen, H. 

Liao and B. C. Cai, “A MEMS-based piezoelectric power generator 

array for vibration energy harvesting”, Microelectronics Journal, vol. 

39, no. 5, pp. 802–806, 2008. 

[53] M. Karen, K. M. Goeders, J. S. Colton and L. A. Bottomley, 

“Microcantilevers: Sensing chemical interactions via mechanical 

motion”, Chemical Reviews, vol. 108, no. 2, pp. 522-542, 2008. 

[54] D. R. Baselt, B. Fruhberger, E. Klaassen, S. Cemalovic, C. L. Britton 

Jr., S. V. Patel, T. E. Mlsna, D. McCorkle and B. Warmack, “Design 

and performance of a microcantilever-based hydrogensensor”, Sensors 

and Actuators B: Chemical, vol. 88, no. 2, pp. 120–131, 2003. 

[55] C. H. Xu, S. Q. Shi and C. Surya, “Gas sensors based on 

one-dimensional nanostructures”, In: Chapter 30 of Handbook of 

nanoceramics and their based nanodevices, Tseng, T.Y. and Nalwa, 

H.S. (eds.), American Scientific Publication, Los Angeles, USA, vol. 

20, pp. 1–22, 2008. 

[56] P. Qi, O. Vermesh, M. Grecu, A. Javey, Q. Wang, H. Dai, S. Peng and 

K.J. Cho, “Toward large arrays of multiplex functionalized carbon 

nanotube sensors for highly sensitive and selective molecular 

detection”, Nano Letters, vol. 3, no. 3, pp. 347–351, 2003. 

[57] J. Huang and Q. Wan, “Gas Sensors Based on Semiconducting Metal 

Oxide One-Dimensional Nanostructures”, Sensors, vol. 9, pp. 

9903-9924, 2009. 

[58] M. Endo, M. S. Strano and P. M. Ajayan, “Potential applications of 

carbon nanotubes, Topics in applied physics”, vol. 111, pp. 13-61, 

2008. 

[59] H. Kikuchi, O. Takahashi, K. Kondo, T. Yamabayashi, K. Oqasawara, 

T. Ishiqaki, Y. Hienuki, M. Nakamura, and A. Subaqyo, “Field-effect 

transistor and method for manufacturing the same”, US Patent no. 

8288804, 2012. 

[60] J. Kong, N. R. Franklin, C. Zhou, M. G. Chapline, S. Peng, K. Cho, 

K.and H. Dai, “Nanotube molecular wires as chemical sensors”, 

Science, vol. 287, pp. 622–625, 2000. 

[61] S. Liu, Q. Shen, Y. Cao, L. Gan, Z. Wang, M. L. Steigerwald, and X. 

Guo, “Chemical functionalization of single-walled carbon nanotube 

field-effect transistors as switches and sensors”, Elsevier: 

Coordination Chemistry Reviews, vol. 254, no. 9-10, pp. 1101-1116, 

2010. 

[62] V. E. Bochenkov and G. B. Sergeev, “Sensitivity, Selectivity, and 

Stability of Gas-Sensitive Metal-Oxide Nanostructures”, In: Chapter 2 

of Metal oxide nanostructures and their applications, Umar, A. and 

Hahn, Y.B. (eds.), American Scientific Publishers, Los Angeles, USA, 

vol. 3, pp. 31-52, 2010. 

[63] http://www.honeywellanalytics.com/en-GB/gasdetection/principles/P 

ages/gasprinciples.aspx 

[64] http://www.delphian.com/sensor-tech.htm 

[65] H. Bai and G. Shi, “Gas Sensors Based on Conducting Polymers”, 

Sensors, vol. 7, pp. 267-307, 2007. 

AUTHORS PROFILE 

Mr. Anish Kumar, B.Tech. (ECE) 

Junior Research Fellow, 

CSIR-CIMFR, Dhanbad 

Research Area: Sensors and Wireless Sensor Network. 

eranishkumar@gmail.com 

Mr. T M Giri Kingson, B.Tech. (AEI) 

Project Assistant, 


Research Area: Sensors, Underground Coal Gasification. 

kingson.giri@gmail.com 

Mr. Rajkumar Prasad Verma, B.Tech. (CSE) 



Research Area: Wireless Sensor Network and Cloud 

Computing. 

rajk.cimfr@gmail.com 

Mr. Abhishek Kumar, B.Tech. (EIE) 



Research Area: Underground Coal Gasification, Gas 

Sensors. 

abhishek2008.indore@gmail.com 

Mr. Subhadip Dutta, B.Tech. (CSE) 

Junior Research Fellow, 


Research Area: Algorithm, Wireless Sensor Network. 

dutta.sdip@gmail.com 

Mr. Ranjeet Mandal, B.Tech. (EIE) 

Project Fellow, 


Research Area: Sensors, Underground Coal gasification, 

Automation. 

ranjeetmandal145@gmail.com 

Dr. Swades kumar Chaulya, B. Tech., M. Tech., Ph.D. 

(IIT, BHU) 

22

ISSN 2249-6343 



Scientist 


Research Area: Wireless Communication, Control 

Monitoring Automation in Underground Mines. 

chaulyask@yahoo.co.in 

Dr. Girendra Mohan Prasad, M.Sc., Ph.D. (ISM, 

Dhanbad) 

Sr. Principal Scientist 


Research Area: Mine Instrumentation and 

Communication. 

prasadgm@yahoo.com 

23

Application of Gas Monitoring Sensors in Underground Coal Mines ...

Create successful ePaper yourself

Delete template?

Save as template?