Presentation5.presentation on mine gases

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1. MINE GASES 1 Source: A manual on mines rescue, safety and gas detection / J. Strang, P. Mackenzie-Wood

2. MINE GASES Measurement Gases are commonly measured in percentage (%) by volume and ppm. Since both of these units of measurement are volume relationships, they are easily converted to one another. Basic formula . % X 10000 = ppm, and conversely ppm ÷ 10000 = % Contamination limits are only quoted in milligrams per cubic metre (mg/m3). The following formula is used to convert concentrations from ppm at 20oC to mg/m3. “M” refers to the molecular weight of the gas. 24.04 is a constant. mg/m3 = (ppm x M) ÷ 24.04 To calculate the equivalent Saskatchewan 8-hour contamination limit in ppm use the following formula: ppm = (mg/m3 x 24.04) ÷ M Co 2

3. MINE GASES Carbon dioxide 3

4. MINE GASES Carbon dioxide 4

5. MINE GASES Carbon Monoxide Health effects : Carbon monoxide is highly toxic. Inhaled carbon monoxide readily binds to blood hemoglobin reducing the blood’s oxygen carrying capacity ( carboxyhemoglobin ). As with other toxic gases, the level and duration of exposure determines the severity of the effects. Health effects of exposure to carbon monoxide include : 400 ppm : temporal headache develops after two to three hours of exposure 1600 ppm : headache, dizziness and nausea in 20 minutes; collapse and death in two hours 2000-2500 ppm : unconsciousness in about 30 minutes high concentrations may provide little or no warning before collapse; deafness has been reported after severe CO intoxication Co 5

6. MINE GASES Co 6 Contamination limits : The 8-hour average limit for carbon monoxide is 29 mg/m3 or 25 ppm ( The Occupational Health and Safety Regulations, 1996 ). For underground operations, the limit for carbon monoxide is 25 ppm Properties : Carbon monoxide is flammable, colourless, tasteless and odourless. It has an explosive range of 12.5 to 74 percent. Such concentrations are unlikely to result from a mine fire unless the fire is confined and is oxygen starved. High concentrations of carbon monoxide may be partially responsible for the event known as backdraft.

7. MINE GASES Origin : Carbon monoxide is a product of incomplete combustion of carbon based materials. The burning or detonation of explosives also produces carbon monoxide, and it is emitted from the exhaust of internal combustion engines . Detection methods: Electronic gas detectors and direct reading colourimetric tubes are available for carbon monoxide. Electronic gas detectors are better for the lower concentrations experienced in the normal working environment . Co 7

8. MINE GASES Exposure effects: Absorption of Co into the blood stream depends upon: Exposure time Gas concentration Work being performed Exercise, high temperature, humidity and emotional stress tend to increase the heart rate and thus the absorption of Co. Acclimatization Degree of saturation b= 4ate/100 B = blood saturation by carboxyhaemoglobin as a % A = Co concentration in ppm T = time of exposure in hours E = factor showing activity: 1 = at rest 2 = Walking 3 = Moderate work Co 8

9. MINE GASES Co 9 Physiological effects of exposure to carbon monoxide (CO)