mine gases atmospheric testing c.4. contributed by: richard black industrial scientific corp
Post on 26-Mar-2015
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Definitions
LEL: Lower Explosive Limit - % LEL
PPM: Parts Per Million - toxic gas measurement
PEL: Permissible Exposure Limit -
8 hr/day - 40 hrs/wk - (OSHA) TWA: Time Weighted Average - 8hr/day- (ACGIH)
STEL: Short Term Exposure Limit -
15 mins/4x shift - (w/ 1 hr break - ACGIH)
IDLH: Immediately Dangerous to Life and Health 30 mins - (NIOSH)
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MIDDLE
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Where will the gases be?Where will the gases be?
Lighter than air:Lighter than air:
MethaneMethane
AcetyleneAcetylene
Carbon monoxide (slightly)Carbon monoxide (slightly)
Heavier than air:Heavier than air:
Hydrogen sulfideHydrogen sulfide
Nitrogen dioxideNitrogen dioxide
Nitric oxideNitric oxide
Carbon dioxideCarbon dioxide
Atmospheric Testing
Atmospheric Testing Combustible Gas - Methane Oxygen - Normal 21%
Low limit 19.5% High limit 23.5%
Toxic gases - Measured in ppm - 10,000ppm=1% Carbon monoxide Nitrogen dioxide Nitric oxide Hydrogen sulfide
Fire TriangleApproved Gas Instruments:
fuel oxygen
source of ignition
detect the combustible gas (fuel)
detect oxygen level (air)
are intrinsically safe (not source of ignition)
COMBUSTIBLE ATMOSPHERES
Combustible LELMethane (natural gas) 5.0% volPropane 2.1% vol Pentane (gasoline) 1.4% volButane 1.9% volHexane 1.2% volMethanol 6.0% volHydrogen 4.0% vol
Common Combustibles
COMBUSTIBLE ATMOSPHERES
100% LEL UEL
0 5.0 15 100% Vol
Example of Combustion
(Fire damp)
Methane (CH4)
Too Lean to Burn
Explosive Mixture
Too Rich to Burn
Oxygen Deficiency
Risk of asphyxiation
Caused byConsumption
firepeopleoxidationdecomposition
Displacementhumidityother gases
Oxygen19.5%
Oxygen Enrichment
Serious fire hazard Materials burn much more rapidly Caused by
leaking valves leaking cylinders Oxygen
23.5%
Effects of Oxygen
23.5% Maximum safe level (OSHA, MSHA)
21.0% Oxygen content in “Air” (20.954%)
19.5% Minimum safe level (OSHA, MSHA)
17.0% Impairment of judgement begins
16.0% First signs of Anoxia
16-12% Breathing and pulse rate increase,
coordination is impaired
Effects of Oxygen
14-10% Fatigue, disturbed respiration
10-6% Nausea and vomiting, inability to move
freely and loss of consciousness
<6% Convulsive movements and gasping
respiration occurs; respiration
stops/minutes later heart action ceases
3-5%Life expectancy; 3 - 5 minutes
Toxic Gases
Pose a threat to human life - react in the body in a
poisonous fashion
Enter the body through various ways, they can be
ingested, injected, inhaled or absorbed through the
skin
Can react with different body systems
Often colorless and odorless
Toxic Gases
Measured in parts per million (ppm)
10,000ppm = 1.0 % by volume
Exposure risks depend on two factors
Concentration (ppm)
Time exposed
Carbon Monoxide Data CO: Colorless, odorless, tasteless, byproduct of
incomplete combustion Hazard: Flammable, LEL 12.6% – UEL 74% Health: Very Toxic (can be absorbed 200-300
time faster than oxygen by the hemoglobin) Exposures: PEL/TWA 50ppm (action level)
STEL 400 ppm
IDLH 1200 ppm Causes: fire, blasting, gas and diesel engines Specific Gravity = 0.967
Effects of CO
50ppm PEL/TWA, Action level (MSHA) 400ppm Frontal headache in 2-3 hrs
1600ppm Headache and nausea 20 mins Collapse and death in 1-2 hrs
6400ppm Headache, dizziness in 1-2 mins, unconsciousness and death in 10-15 mins
H2S: Colorless, Rotten egg smell Hazard: Flammable, LEL 4.0% - UEL 46% Health: Extremely Toxic, appears naturally from
decomposition, reacts with the enzymes in the blood - inhibits cell respiration Exposure: PEL/TWA 10ppm (action level)
STEL 15ppm
Causes: Groundwater in shaftCauses: Groundwater in shaft Specific Gravity = 1.2Specific Gravity = 1.2
Hydrogen Sulfide Data
Effects of H2S
..13ppm - Minimal perceptible odor
10ppm - PEL,TWA, Action level (MSHA) Beginning of eye irritation
100ppm - Coughing, eye irritation, loss of sense of smell after 2-5 minutes
500ppm - Loss of consciousness and possible death 30 mins - 1
hr
Nitrogen Dioxide Data
NO2: yellowish-brown gas with a pungent odor
Hazard: will not explode
Health: Extremely toxic Exposures: PEL/TWA 3ppm
STEL 5ppm
Causes: Blasting, diesel powered equipmentCauses: Blasting, diesel powered equipment Specific Gravity = 1.6Specific Gravity = 1.6
Effects of NO2
3ppm - PEL/TWA
5ppm - STEL, Action level (MSHA)
20ppm - Irritation of eyes, nose and throat **
50ppm - Maximum exposure for a 30 mins
200ppm - Tightness of chest, acute bronchitis,
and death in prolonged exposure
High doses can cause pulmonary edema - drown from inside out
** Nitric Acid = NO2 + H2O
Nitric Oxide Data
NO: Colorless gas, typically formed when air is super heated and nitric compound like dynamite explode
Hazards: will not burn, will accelerate burning Health: extremely toxic
– Exposure limit: PEL/TWA 25ppm (action level) STEL N/A
Causes: Blasting, diesel powered equipmentCauses: Blasting, diesel powered equipment Specific Gravity = 1.6Specific Gravity = 1.6
Effects of NO 0-50ppm - irritation of mucus membranes
25ppm - PEL/TWA, Action level (MSHA)
60-150ppm - Irritation is more intense,
coughing and burning of
the throat is evident,
symptoms will clear if
victim is removed quickly to
clean air.
200-700ppm - May be fatal even after very
short exposures.
Sulfur Dioxide Data
SO2: Colorless gas, irritating pungent odor Hazards: will not explode, can combine with
water to form sulfuric acid (H2SO4) Health: extremely toxic
Exposures: PEL/TWA 2ppm STEL 5ppm
Source: Hardrock mine strata Specific Gravity = 2.2
Effects of SO2
.3-1ppm - Initially detected by taste
2ppm - PEL/TWA
5ppm - STEL
20ppm - Irritation of nose, throat and eyes
**
100ppm - Maximum exposure for 30 mins** Sulfuric Acid (H2SO4) = SO2 + H2O
Hydrogen Cyanide Data
HCN: Colorless to a pale blue gas Hazard : will explode - LEL 5.6% - UEL 40% Health: extremely toxic, has a distinct odor
resembling bitter almonds Exposures: PEL/TWA 10ppm
STEL N/A
Sources: Leaching of precious metals,Metal mining
Specific Gravity = 0.69
Effects of HCN
10ppm Permissible Exposure Limit
5-10ppm Headache, dizziness,
unsteadiness
50-100ppm Feeling of suffocation, nausea
100-200ppm Death from exposure in 30 to
60 minutes
Ammonia Data
NH3: colorless gas with a suffocating odor Hazards: Difficult to burn, LEL 15% - UEL 28% Health: extremely toxic
Exposures: PEL/TWA 25ppm STEL35ppm
Effects of NH3
0-25ppm - Minor irritation of the eyes
and respiratory tract
25ppm - PEL/TWA
50-100ppm - Swelling of the eyelids,
conjunctivitis, vomiting,
irritation of the throat
100-500ppm - Very dangerous concentrations,
death from prolonged exposure
Carbon Dioxide Data
CO2: byproduct of complete combustion, present in the atmosphere (about 400ppm), acidic taste
Hazard : Non-flammable Health: simple asphyxiant Exposures: PEL/TWA 5000 ppm
STEL 30,000 ppm
Causes: Combustion, respiration, decomposition Specific Gravity = 1.5
Effects of CO2
400ppm - Approx.. ambient level
3,000-5,000ppm - Low concentrations cause
increased respiration and
headaches
8,000-12,000ppm - Headache, nausea, vomiting,
and if not given air or oxygen,
possible unconsciousness
>15,000ppm - High concentrations cause
rapid circulatory insufficiency
leading to coma and death
Review Questions (Answers on the next slide)1. What gas is the most plentiful in normal air?
a. Nitrogenb. Oxygenc. Carbon dioxided. none of the above
2. How much methane is required for an explosion to occur?a. 5% - 15%b. 15% - 20%c. 5% - 75%d. 10% - 100%
3. Which of the following gases are produced in diesel engine exhaust?a. Nitrogen dioxideb. Nitric oxidec. Carbon monoxided. all of the above
4. Which of the following gases is heavier than air?a. Methaneb. Acetylenec. Hydrogen Sulfided. None of the above
Answers to Review Questions1. What gas is the most plentiful in normal air?
a. Nitrogen
2. How much methane is required for an explosion to occur?
a. 5% - 15%
3. Which of the following gases are produced in diesel engine exhaust?
d. all of the above
4. Which of the following gases is heavier than air?
c. Hydrogen Sulfide
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