06---Saturday---Gasses Questions 3 Flashcards
Name two higher hydrocarbons?
Propane C3H8 and Ethylene C2H4
What is benzene?
Higher hydrocarbon C6H6 clear, colourless, aromatic smell (tarry), soluble in water SG- .88
When would benzene normally be detected?
Above 200o C
What are nitrous fumes?
Mixture of oxides of nitrogen as found in mines
Where are they likely to be found?
Diesels, shot firing
What is the typical composition of water gas?
45% Hydrogen 45% Carbon Monoxide Smaller amounts of CO2, CH4, N2, O2
How is water gas formed?
Pass steam over red hot coal (1200- 1400 C)
What is the explosive range of water gas?
Lower explosive limit (LEL)6-9% upper explosive limit (UEL) 70%
What is the typical composition of producer gas?
10% CO2, 15% CO, 74%N2 1% other gases eg CH4
How is producer gas formed?
Air passing through a layer of incandescent coal.
What are aldehydes?
Organic compounds of carbon hydrogen oxygen.
Where is aldehydes found?
Exhaust gases from diesel engines.
What are fumes?
Gas and smoke , noxious or poisonous gases ,
How are fumes formed?
By the burning of substances to the required heat to give off fumes
What is fire stink?
A benzene associated odour that indicates spont com
Briefly describe fire damp?
Flammable gas produced by the decomposition of coal or other carbonaceous matter generally methane but can include H2, CO, CO2 From mine strata including floor
Briefly describe black damp?
Carbon Dioxide and Nitrogen atmosphere depleted of oxygen
How is black damp generated?
Oxidation of coal or timber oxygen is absorbed and carbon dioxide is given off
What is the average concentration of the constituent gases of black damp?
Carbon Dioxide 10%- 15% Nitrogen 85%- 90%
Briefly describe choke damp?
Methane or carbon dioxide insufficient oxygen
How is choke damp generated?
By large emissions of gas from the strata displacing the air
Briefly describe after damp?
Gas left in the atmosphere on the return side of a fire
How is after damp generated?
an explosion of gas or coal dust and gas N2 little O2,CO, CO2
Briefly describe white damp?
Lethal quantities of carbon monoxide
How is white damp generated?
Methane or coal dust explosions, mine fires, water gas, producer gas
Briefly describe stink damp?
Hydrogen Sulphide in the air
How much oxygen is present in normal atmosphere?
20.93%
What is the legal limit for oxygen in underground coal mines?
19%
What type of sensor is installed in multigas hand held instruments to detect oxygen?
electrochemical sensor
What effect does an atmosphere enriched with oxygen have on the UPPER FLAMMABLE LIMIT of flammable gases?
raises
There two different types of sensors that can be used in a multigas hand held instrument. One is called a volumetric sensor. What is the other type?
partial pressure
Is a volumetric type oxygen sensor affected by variations in the atmospheric pressure?
no
How much nitrogen is present in normal atmosphere?
78.11%
With a volumetric type sensor, what effects will the presence of carbon dioxide (higher than normal) have on the oxygen reading?
Make the reading incorrect
What is the legal limit for nitrogen in Queensland underground coal mines?
n/a
Under normal conditions, what effect does nitrogen have on the human body?
None
Will nitrogen support life?.
no
How is nitrogen detected in Queensland underground coal mines?
Gas chromatograph
What is the explosive range for methane
5%- 14%
What percentage of methane will produce the most violent explosive mixture when mixed with air?
9.50%
What is the most easily ignited mixture of methane in air (by an electric arc) ?
7.50%
What is the ignition temperature of methane?
595oC
Lag of ignition is a term referred to the ignition of a flammable gas/air mixture. What is meant by the term lag of ignition?
Time it takes from when the flammable mixture is introduced to the heat source to the time it ignites
What is the minimum concentration of oxygen for a methane explosion to occur?
12.40%
Methane has a long lag in ignition when compared to most flammable gases. What is the lag time for a 5-6 % methane/air mixture?
2 seconds
State where methane would be found in an underground coal mine.
Seam gas, face areas, sealed areas, cut coal,
What physiological effect does methane have on humans?
none
Name two types of methamometers used to detected methane in Queensland underground coalmines?
catalytic combustion, infra red analyser
Which of these methamometers is most reliable where other flammable gases are present or oxygen is deficient?
Infra red analyser
What is the normal measuring range for wheatstone bridge or pellister (Catalytic oxidation principle) type methanometers?
0%- 5%
What percentage of carbon monoxide will produce the most violent explosive mixture when mixed with air?
29%
What is the legal limit for carbon monoxide in Queensland underground coal mines?
30ppm
What type of sensor is installed in hand held electronic instruments to detect carbon monoxide?
Electrochemical sensor
State where carbon monoxide would be found in underground coal mines.
Heatings, explosions, fires
Is this carbon monoxide sensor cross sensitive to other gases?
Yes H2, H2S
What is meant by the term cross sensitive?
When other gases interfere with the gas being sampled eg 100ppm H2 reads 31 ppm CO
Name another type of hand held instrument that can be used to detect Carbon monoxide.
Detector tube –white- brownish green
How is the human body poisoned by carbon monoxide?
CO poisons the blood by being absorbed into the blood stream and preventing blood taking up and transporting oxygen to various cells and organs
In regards to carbon monoxide poisoning, what is meant by the term blood saturation?
As CO is absorbed into the blood stream 300 time more readily than O2 there is less available red blood cells to absorb oxygen so the blood becomes saturated
Carbon monoxide poisoning is said to have a cumulative effect. What is meant by cumulative effect?
As a person is exposed over a number of short terms the blood absorbs some of the gas each time and it accumulates in the blood if the person hasn?t had enough time in fresh air to dilute the gas in the blood
Name six signs and symptoms that would be associated with carbon monoxide poisoning.
Headache, nausea, unsteady gait, Giddiness, difficulty breathing, palpitations
What is the legal limit for carbon dioxide in Queensland underground coal mines?
1.25%
How much carbon dioxide is present in normal atmosphere?
0.03%
Name three ways in which carbon dioxide is produced in underground coal mines.
Seam gas, oxidation, breathing
Carbon dioxide is regarded as a hot gas due to its low thermal conductivity. Explain the term low thermal conductivity
Heat is not conducted away as rapidly as normal air.
What type of sensor is installed in hand held electronic instruments to detect carbon dioxide?
Infra red analyser
What other type of hand held instrument can be used to detect carbon dioxide?
Detector tube–white- violet
Why can,t Electrochemical cell sensors be used to detect carbon dioxide?
Regarded as unreliable
What is the explosive range for hydrogen?
4%- 74%
What is the legal limit for hydrogen in Queensland underground coal mines?
n/a
State five reasons why hydrogen is considered the most dangerous of all flammable gases.
Wide flammable range, almost absent lag of ignition, almost instant build up of maximum pressure, Low energy for ignition, low ignition temperature
State three places where hydrogen may be found in underground coal mines.
Battery charging, behind seals, Spont com
What effect does hydrogen have on the human body?
None
How is the presence of hydrogen detected in underground coal mines?
Gas chromatograph
What is the explosive range for hydrogen sulphide?
4.5% - 45%
What is the legal limit for hydrogen sulphide in Queensland underground coal mines?
Long term exposure 10 ppm Maximum exposure 15 ppm .
What effect does hydrogen sulphide have on the human body?
irritates the lungs and respiratory tract narcotic effect on the nervous system
What type of sensor is installed in hand held electronic instruments to detect hydrogen sulphide?
electrochemical sensor cross sensitive to Hydrogen
State where hydrogen sulphide would be found in underground coal
seam gas, stagnant water, goaf fires ( high sulphur coal )
What other type of hand held instrument can be used to detect hydrogen sulphide?
Detector tube
What is the legal limit for sulphur dioxide in Queensland underground coal mines?
Long term exposure Ans. 2ppm, maximum exposure Ans. 5ppm
State where sulphur dioxide would be found in underground coal mines.
heatings
What effect does sulphur dioxide have on the human body?
irritates eyes and respiratory tract
What type of sensor is installed in hand held electronic instruments to detect sulphur dioxide?
Electrochemical sensor
What other type of hand held instrument can be used to detect sulphur dioxide?
Detector tubes
What is the legal limit for nitrogen dioxide in Queensland underground coal mines?
Long term exposure 3ppm Maximum exposure 5ppm
State where oxides of nitrogen would be found in underground coal mines.
Diesel exhaust, Shotfiring
What effect does oxides of nitrogen have on the human body?
Irritates the lungs and air ways
Oxides of nitrogen causes the following physiological effects on the
human body. State percentages.
If the human body is exposed to 150 PPM of oxides of nitrogen, what medical condition may develop several hours after exposure.
Broncho pneumonia
What type of sensor is installed in hand held electronic instruments to detect nitrogen dioxide?
electrochemical sensor
What other type of hand held instrument can be used to detect oxides of Nitrogen?
Detector tube–light grey- bluish grey
