Gas Exam - Part 4

Question 1

What are the physical properties of SO2?

Answer 1

Colourless, pungent suffocating smell, acidic taste

very water soluble

Question 2

Where does SO2 occur in mines?

Answer 2

Heating’s or fires where the coal contains sulphur

Diesel exhausts

Question 3

Is SO2 flammable?

Answer 3

No

Question 4

What are the physical/ chemical properties of NO2?

Answer 4

Reddish brown in colour, Acrid smell, Acidic Taste

Water soluble

Question 5

What is the maximum exposure of NO2?

Answer 5

TWA – 3ppm

STEL – 5ppm

Question 6

Where does NO2 occur in mines?

Answer 6

Diesel exhausts

Shotfiring

Question 7

Although NO2 is not flammable what does it support?

Answer 7

Not flammable but will support combustion

Question 8

Name the different sampling/sensor methods used for

OXYGEN
O2

Answer 8

Electrochemical (Partial pressure & volumetric), G.C, Paramagnetic

Question 9

Name the different sampling/sensor methods used for

CARBON MONOXIDE (CO) &
CARBON DIOXIDE (CO2)

Answer 9

Tube detectors, Infared, G.C

All - IDE’s Tube detectors

Question 10

Name the different sampling/sensor methods used for

METHANE
CH4

Answer 10

Infa-red, thermal conductivity & catalytic combustion methanometers, G.C

Question 11

Name the different sampling/sensor methods used for

NITROGEN
N2

Answer 11

G.C

Question 12

Name the different sampling/sensor methods used for

NITROGEN DIOXIDE (NO2)
HYDROGEN SULPHIDE (H2S)
SULPHUR DIOXIDE (SO2)

Answer 12

Tube detectors, Electrochemical

All - IDE’s Tube detectors

Question 13

What is the minimum % O2 for a catalytic combustion sensor?

Answer 13

10 %

Question 14

What should a personal gas detector read for O2?

Answer 14

20.9%

Question 15

What effects does the barometric pressure have on a volumetric sensor?

Answer 15

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.

Question 16

What effect does high humidity have on an O2 sensor?

Answer 16

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%

Question 17

Name 2 gasses that have cross interference with a CO sensor

Answer 17

H2, H2S

Question 18

What is the range of the wheatstone bridge sensor?

Answer 18

0 – 5%

Question 19

Name 2 advantages of infared over catalytic combustion CH4 sensor?

Answer 19

Not poisoned by other gases

Operates in low O2 backgrounds

Question 20

How often does a personal gas detector have to be tested?

Answer 20

Spanned at the start of every shift

Question 21

How often are personal gas detectors calibrated by NATA?

Answer 21

6 monthly

Question 22

Why don’t you breathe over the sensors of a personal gas detector?

Answer 22

Exhaled CO2 and moisture poisons the sensors. It shortens the cell life through the destruction of the electrolyte

Question 23

How would an O2 sensor react travelling from pit top to pit bottom?

Answer 23

Reading would increase, a decrease of 40m in altitude will increase the reading by 0.1%

Question 24

How should electronic – real time sensors be cleaned?

Answer 24

A damp cloth and a brush

Question 25

What is the best time to take a bag sample?

Answer 25

During the falling barometer 2-4 pm/am

Question 26

What measures the atmospheric pressure?

Answer 26

Barometer