Abstract : Safety plays a major role in today’s world and it is necessary that good safety systems are to be implemented in places of education and work. This work modifies the existing safety model installed in industries and this system also be used in homes and offices. The main objective of the work is designing microcontroller based toxic gas detecting and alerting system. The hazardous gases like LPG and propane were sensed and displayed each and every second in the LCD display. If these gases exceed the normal level then an alarm is generated immediately and also an alert message (SMS) is sent to the authorized person through the GSM. The advantage of this automated detection and alerting system over the manual method is that it offers quick response time and accurate detection of an emergency and in turn leading faster diffusion of the critical situation.
The electrode, as the key part, is a gas diffusion electrode made of noble metals.
In this device the electric current between the working electrode and the opposing electrode is proportional to the concentration of the toxic gas.
This sensor has been widely used in detecting the gases mentioned above, especially in both fixed site and portable detectors.
Semiconductor sensors are prepared as sintered, thick or thin films by the deposition of noble metal catalysts, such as platinum, palladium, ruthenium, gold, etc., onto semiconductor materials, such as ferric oxide, zinc oxide, stannic oxide or indium oxide
Lundstrom in Sweden prepared hydrogensensitive metal oxide semiconductor (MOS) field effects sensors by using a palladium metal grid material and later Armagarth found that this structure is also sensitive in some degree to hydrogen sulphide and ammonia . As this is suitable for microprocessing and integration widespread interest has been aroused It is usually considered that hydrogen containing compounds, including hydrogen sulphide, It is usually considered that hydrogen containing compounds, including hydrogen sulphide, ammonia and hydrogen cyanide, dissociate out atomic hydrogen on the semiconductor grid (palladium or other noble metals) and that atomic hydrogen diffuses into the inner surface of the noble metals grid.
Decomposition of organic matters in sewers, manholes and pits of the drainage system will generate methane and/or hydrogen sulphide.
Hydrogen sulphide, being very soluble in water, often dissolves in sewage and can be trapped within sediment and sludge in sewers as gas pockets.
Disturbing the sewage, sediment or sludge can release the trapped or dissolved gas.
Leaks from underground fuel tanks, gas utility pipes, connected sewer systems or contaminated land, such as landfills, may enter the work area.
Use of generators and fuel-driven tools in poorly ventilated areas may use up oxygen and generate carbon monoxide.
Only properly maintained and calibrated equipment should be used for atmospheric testing.
Unscientific methods such as throwing a flame down the manhole, and observing the presence of living organisms or the colour of manhole are unreliable.
• The most common configuration for a multiple-sensor gas monitor is one that can read levels of oxygen, combustible gases, hydrogen sulphide and carbon monoxide.
Never assume that the hazardous gases present are limited to these gases.
Different or additional air monitoring instruments are required for other hazardous gases that may be present in the drainage.
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