Gas Exam - Part 4 Flashcards
What are the physical properties of SO2?
Colourless, pungent suffocating smell, acidic taste
very water soluble
Where does SO2 occur in mines?
Heating’s or fires where the coal contains sulphur
Diesel exhausts
Is SO2 flammable?
No
What are the physical/ chemical properties of NO2?
Reddish brown in colour, Acrid smell, Acidic Taste
Water soluble
What is the maximum exposure of NO2?
TWA – 3ppm
STEL – 5ppm
Where does NO2 occur in mines?
Diesel exhausts
Shotfiring
Although NO2 is not flammable what does it support?
Not flammable but will support combustion
Name the different sampling/sensor methods used for
OXYGEN
O2
Electrochemical (Partial pressure & volumetric), G.C, Paramagnetic
Name the different sampling/sensor methods used for
CARBON MONOXIDE (CO) & CARBON DIOXIDE (CO2)
Tube detectors, Infared, G.C
All - IDE’s Tube detectors
Name the different sampling/sensor methods used for
METHANE
CH4
Infa-red, thermal conductivity & catalytic combustion methanometers, G.C
Name the different sampling/sensor methods used for
NITROGEN
N2
G.C
Name the different sampling/sensor methods used for
NITROGEN DIOXIDE (NO2) HYDROGEN SULPHIDE (H2S) SULPHUR DIOXIDE (SO2)
Tube detectors, Electrochemical
All - IDE’s Tube detectors
What is the minimum % O2 for a catalytic combustion sensor?
10 %
What should a personal gas detector read for O2?
20.9%
What effects does the barometric pressure have on a volumetric sensor?
Decrease by 5 millibar will decrease the reading by 0.1%. Little or no real effect. But if a rapid change in pressure occurs must let it stabilise for true reading. Eg intake to return pit bottom.
What effect does high humidity have on an O2 sensor?
Reduces amount of O2 available in partial pressure cell causing a low reading by dilution. Increase in humidity by 10% will decrease O2 reading by 0.1%
Name 2 gasses that have cross interference with a CO sensor
H2, H2S
What is the range of the wheatstone bridge sensor?
0 – 5%
Name 2 advantages of infared over catalytic combustion CH4 sensor?
Not poisoned by other gases
Operates in low O2 backgrounds
How often does a personal gas detector have to be tested?
Spanned at the start of every shift
How often are personal gas detectors calibrated by NATA?
6 monthly
Why don’t you breathe over the sensors of a personal gas detector?
Exhaled CO2 and moisture poisons the sensors. It shortens the cell life through the destruction of the electrolyte
How would an O2 sensor react travelling from pit top to pit bottom?
Reading would increase, a decrease of 40m in altitude will increase the reading by 0.1%
How should electronic – real time sensors be cleaned?
A damp cloth and a brush
