Introduction
Gas Detectors Explained: How They Keep Us Safe
Gas detector is very commonly used equipment for safety purpose. As name itself explain the purpose of gas detector, it is widely used to detect the harmful , dangerous and life-threatening gases present in workplace. During maintenance work and routine work if there is possibility of gas presence , detectors are used to detect the gas. Specially chemical, there is danger in many activity places or even in the house, then they do not give warning. Some kind of gas like toxic gas, flammable gases etc. are unpleasant, they do not even smell, in that case the role of gas detector comes into play, which ensures our safety by becoming a guide, monitors the air around us and alerts us about the dangers before it gets too late.
What is gas detector?
Gas detector is a device which detect the presence of gases often as part of Safety system. it is portable as well as online also. it is very important equipment specially for chemical factory, petrochemical factory and pharmaceutical company. these devices generally used to detect following gases:
- Toxic gases: Like carbon di sulphide, carbon monoxide, amonia, hydrogen sulphide etc.
- Oxygen Level : Oxygen Concentration in workplace area.
- Combustible Gases:- Methane, Propane, Ethylene oxide etc.
Whenever a gas detector detect the gas it gives the alarm or annunciate the hooter or siren to take action whether it is evacuating, ventilating the area or fixing the leak.
How Do gas detector work?
Basically the detectors have a sensor element which react to specific gases in air. there are several technologies or principal of operation of detectors, each suited for different environment.
Following sensor technologies used in gas detection system:
Electrochemical sensors.
used to detect the toxic gases present in workplace or area of concern e.g. CO and H2S and this sensor generate the electric current when exposed with gases and detector measures this and convert it in a output signal to display.
Infra Red (IR) Sensors.
Used in such area or for gases where catalytic bead sensor not work well. such type of sensor detector used to detect the hydrocarbon gases.
Catalytic Bead sensor.
Commonly used to detect the flammable gas like ethylene oxide, propane etc. They oxidize the detect gases on heated beads which change resistance and give a output as alert .
Photoionization Detector
Generally used to detect the volatile organic gases and some kind of toxic gases which use the UV gases to ionize the molecule
When and Where gas detector used ?
As we know gas detector detect the Presence of some harmful gases while performing routine and non routine work like daily operations, maintenance work, project work and some are online fixed where life threatening gases may leak during normal operation. generally Gas detector are used in following work:-
- Confined Space work:- Confined space work is most dangerous work with respect to safety point of view. it requires the continues gas monitoring while someone is in inside. Confined space may contain the CO, H2S, Methane, etc.
- During Hot work:- area or site which a great possibility of explosive gases present or flammable gases present are also require the continues monitoring of workplace.
- Toxic Release of Chemical: Toxic chemical release area are facilitated by gas detector to early detection of the same.
- Emergency Situation:-Portable or Individual gas detector used in emergency situation to handle the case.
What does it means the PPM and LEL % in gas detector ?
Gas detector work on different principal as previous discussed. Each gas detector after detecting the supposed gas in surrounding area or area of concern, it shows the gas concentration in either in PPM or % LEL. Except Oxygen detector, all the gas detectors show some reading when sensor exposed with gases. PPM Reading gas detector shows the gas concentration in PPM value. based on acceptable Level of specific gas in PPM concentration, we can take appropriate action. Some detectors are show the gas concentration in % LEL of v/v. As we Know, each and every gas have their own explosive range as difference between LEL and UEL. Generally catalytic bead type sensor shows the reading as % LEL. it means if a detector, calibrated with Methene gas, it shows the gas concentration in surrounding area is 20% of LEL v/v, it addresses as the reading are 20% of methane gas LEL. To know the actual gas concentration, we have to multiply the correction factor for that specific value with Reading and then we get the actual value of specific gas concentration in surrounding area.
How can one interpret the % LEL reading if detector shows some reading in display ?
Whenever a sensor of Catalytic bead sensor technology’s detector exposed with gases, it shows some reading in display. for Example, if sensor is Calibrated with Methan gas and detector is installed in a area where Ethylene oxide gas may present or could leak. if Eto is leak then detector shows the reading as 20% of LEL. it means the surrounding area have a Eto concentration but the reading 20% does not means it is 20% of LEL of Eto, it means that a explosive mixture present around the detector. because of the detector calibrated with Methane, if wants to know the actual concentration of Eto , then we have to multiply this reading ,20 with a equivalence or correction factor , suppose correction factor is 1.5 , then concentration of Eto is 20x 1.5 =30 % of LEL . Now we know the LEL of Eto is 2.6 %, then actual concentration of Eto is , 30% of LEL of ETO 2.6 . it gives the results as 2.6×30/100= 0.78 % of Eto v/v present in surrounding area.
Calibration and Maintenance of Detector
Each and Every gas detector whether it is portable or online shall be calibrated with its specific gas or gas mixture. because of detectors are very crucial part of safety Management system which dierctly connected to life of human or person working at workplace. We should use the calibrated gas detector at our workplace because the reading of detector matters for safety point of view. generally, all the gas detectors are calibrated twice in a year.
Interesting fact about gas detector ?
Catalytic bead sensor detector needs atleast 16% Oxygen level to perform the function.