MARTIN CHIKAMHI

F.B.L. GUIDELINE(NOTES)

MIMOSA MINE

Bsc (Hon) MINING ENGINEERING

UNIVERSITY OF ZIMBABWE

GASES

1. Oxygen

2. Nitrogen3. Hydrogen4. Carbon dioxide5. Carbon monoxide6. Nitrous fumes7. Methane8. Hydrogen Sulphide9. Ammonia10. Hydrogen cyanide11. Hydrogen chloride12. Sulphur dioxide13. Aldehydes14. Propane15. Acetylene16. Freon17. Chlorine18. Phosgene

Definitions:-

Choke damp =>Atmosphere with high CO-2 content and 0-2 deficiency

Black damp =>An atmosphere deficient in O-2(CO-2,N-xO-y,CH-4,N-2)

After damp => An atmosphere remaining after explosion of CH-4

Fire damp => An atmosphere with an explosive mixture composing of ‘mathane’ and other gases. E.g. O-2,CO-2,N-2 etc

White damp =>

Watergas =>

1.0 OXYGEN

Sources:--is a normal constituent of air.-Important to preserve life.

Properties:--forms 20.93% of atmosphere.-is colourless, odourless and tasteless.-slightly soluble in water.-supports combustion.

Effects:-20.93% =>Nil, 19% =>Flame of safety lamp reduced by 50%,17% =>Flame of safety lamp extinguished. Slight increase in pulse and respiration rate

observed. 14% =>respiration disturbed, abnormal fatigue upon slight exertion, headaches and dizziness, faulty judgement.- No ill effects observed from oxygen enriched atmosphere.Deficiency caused by U/G fires ,breathing of persons, slow oxidation of timber and is also adsorbed by fine coal(exothermic hence spontaneous combustion)another cause for deficiency is by displacement during N-2 injection during mine fires.

Treatment:-The casualty must be removed to fresh air and resuscitation applied as soon as possible.

Detection:-A flame safety lamp or an electronic detector can be used to detect oxygen deficiency.A drager gas detector.Limit:-The quality of the fresh air intake must be preserved, no drop in O-2 levels must be tolerated.

2.0 NITROGEN

Sources:-Nitrogen injection in U/G fires to eliminate oxygen(old system).- also used as an inert shield in welding.Extreme caution must be exercised around fire seals, as pressure imbalance would transform fresh air(intake) into oxygen deficient atmosphere

Increased N-2 proportions in mine atmospheres are due to oxygen deficiencies, and consequently form the major constituents of After damp and Black damp.

…/Nitrogen.

Properties:-Lighter than air S.G.=>0.97Colourless, odourless and tasteless.Chemically inert.Slightly soluble in water. Effects:-The only adverse effect of nitrogen in the mining environment is the resultant oxygen deficiency.

Treatment:-The victim must be removed (carried) too fresh air as soon as possible with resuscitation applied if necessary.

Detection:-Oxygen content which is easily measured can be used to calculate approx. N-2 conc.

Limit:-No O-2 deficiency must exist.

3.0 HYDROGEN

Sources:-Battery charge bays(2/3 of gases emitted =>H-2).Decomposition of NH-3 at high temp.Incomplete combustion during explosions, U/G fires or blasting operations for temps.>250 deg.

Properties:-Lighter than air.(S.G. =>0.07)Colourless- tasteless-odourless.Non- toxic, does not support combustion but readily combustible.

Flammability:-Burns with a blue flame up to 4%conc.Explodes violently in accumulations between 4% - 74% with burning velocities ranging from 0.02 to 3.35 m/s

Effects:-Same as methane.

Treatment:-As in all asphyxiant gases, resuscitation with oxygen will provide a complete and rapid recovery.(see N-2 and CO-2)

…/Hydrogen.Detection:-There is no available method of detecting and measuring H-2 in the presence of other flammable gases underground. However 500ml samples can be analysed with drager tubes in a gas free atmosphere

Limit:-Can be set as per methane =>1.25%(S.A. Regs.)

4.0 CARBON DIOXIDE (CO-2) ‘‘Miner’s friend ’’

Sources:-* Product of complete combustion *Blasting, breathing, decay of timber, diesel exhaust fumes, u/g fires welding & cutting torch, burning of explosives and explosions.Can also be produced by action of acid waters on carbonate rocks.

Properties:-Normal atmosphere contains 0.03% or 300ppm CO-2colourless - odourless - slight acidic tastesoluble in waterheavier than air ( s.g. =>1.53) toxicdoes not support combustion.Asphyxiant.

Effects:- It is harmful in the following 3 manners. 1.Asphyxiant - will displace oxygen and if in sufficient quantities oxygen deficiency will pose a threat to life 2.Respiratory stimulant - respiratory volume is doubled at 4% CO-2 and redoubled at 5% CO-2 Stimulant and depressant of C.N.S. - will stimulate the CNS by causing palpitation

increased blood pressure and sweating occurs at7.5% headaches, mental depression, visual disturbance shaking, exhaustion, collapse, unconsciousness and death can result from CO-2 overexposure.

Treatment:-Quick removal of victim to fresh air -vital. Resuscitation, oxygen administration, keep warm and no exertion should be tolerated.Professional medical assessment to be obtained as soon as possible.

…/Carbon dioxide

Detection:-Auer gas tester, drager detector pump extinguishes candle at 3%(Flame safety lamp)- turns lime water milky - headache.

Dispersion:-- water blast- auxiliary ventilation(fresh air blown in)- ventilation- watering down

Limit:-5000ppm [0.5%]

5.0 CARBON MONOXIDE

Sources:-* product of incomplete combustion*- blasting- diesel engine (defective)exhaust fumes - u/g fires, methane explosions- fuse ignition- overheated lubricants in air compressors- a constituent of watergas, white damp, afterdamp.

Properties:-- has no warning properties.- is always present if smoke is visible.- colourless, tasteless and odourless.- is lighter than air(s.g. 0.97) but can be encountered in winzes as well as raises.- burns with a blue flame (up to about 12%).- explodes between 12% and 74% at 605 0C.- very poisonous.- slightly soluble in water.- does not support combustion.

Effects:-- gassed persons found (if unconscious) in the state they were when they where attacked.- the poisonous effect of the gas is to rob the body of oxygen which is necessary to preserve life(by formation of carboxy-haemoglobin =>300 time faster than oxy-haemoglobin)- tightness across forehead.-severe headache, weakness, dizziness, dimness of vision, nausea and vomiting and collapse.- increased pulse and respiration, comma with intermittent convulsions, depressed heart action and respiration.-death …/Carbon monoxide

Cumulative effect:-- a person exposed to the gas for a number of short durations within a limited time span will become more and more susceptable to its effects since the absorbed gas would not have had enough time to be expelled from the system.