Transcript Toxic Gases
Mine Gases Atmospheric Testing
Contributed by: Richard Black Industrial Scientific Corp.
C.4.
What is AIR??
Nitrogen (N 2 ) 78% Oxygen (O 2 ) 21% All other gases 1% Total 100%
Definitions
LEL: L ower E xplosive L imit - % LEL
PPM: P arts P er M illion - toxic gas measurement
PEL: P ermissible E xposure L imit 8 hr/day - 40 hrs/wk - (OSHA)
TWA: T ime W eighted A verage - 8hr/day- (ACGIH)
STEL: S hort T erm E xposure L imit -
15 mins/4x shift - (w/ 1 hr break - ACGIH)
IDLH: I mmediately D angerous to L ife and H ealth
30 mins - (NIOSH)
Atmospheric Testing
Where will the gases be?
Lighter than air: Methane Acetylene Carbon monoxide (slightly) Heavier than air: Hydrogen sulfide Nitrogen dioxide Nitric oxide Carbon dioxide TOP MIDDLE BOTTOM
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
COMBUSTIBLE ATMOSPHERES
Fire Triangle
Approved Gas Instruments:
detect the combustible gas (fuel) fuel detect oxygen level (air) are intrinsically safe (not source of ignition) oxygen source of ignition
COMBUSTIBLE ATMOSPHERES
Common Combustibles
Combustible
Methane (natural gas) Propane Pentane (gasoline) Butane Hexane Methanol Hydrogen
LEL
5.0% vol 2.1% vol 1.4% vol 1.9% vol 1.2% vol 6.0% vol 4.0% vol
Example of Combustion
100% LEL UEL
(Fire damp) Methane (CH 4 )
0 5.0
Too Lean to Burn
15
Explosive Mixture Too Rich to Burn
100% Vol
Oxygen Deficiency
19.5% Oxygen
Risk of asphyxiation Caused by Consumption fire people oxidation decomposition Displacement humidity other gases
Oxygen Enrichment
Serious fire hazard Materials burn much more rapidly Caused by leaking valves leaking cylinders
Oxygen
23.5%
Effects of Oxygen
23.5% 21.0% 19.5% 17.0% Maximum safe level (OSHA, MSHA) Oxygen content in “Air” (20.954%) Minimum safe level (OSHA, MSHA) 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% 3-5% Convulsive movements and gasping respiration occurs; respiration stops/minutes later heart action ceases Life expectancy; 3 - 5 minutes
TOXIC GASES
TOXIC GASES
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 IDLH 400 ppm 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
Hydrogen Sulfide Data
H 2 S: 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 shaft Specific Gravity = 1.2
Effects of H
2
S
.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
NO 2 : yellowish-brown gas with a pungent odor Hazard: will not explode Health: Extremely toxic Exposures: PEL/TWA 3ppm STEL 5ppm Causes: Blasting, diesel powered equipment Specific Gravity = 1.6
Effects of NO
2
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
** Nitric Acid = NO 2 + H 2 O
High doses can cause pulmonary edema drown from inside out
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 equipment Specific Gravity = 1.6
0-50ppm -
Effects of NO
irritation of mucus membranes 25ppm 60-150ppm PEL/TWA, Action level (MSHA) 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
SO 2 : 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 SO
2
.3-1ppm - Initially detected by taste 2ppm 5ppm 20ppm PEL/TWA STEL Irritation of nose, throat and eyes ** 100ppm - Maximum exposure for 30 mins
** Sulfuric Acid (H 2 SO 4 ) = SO 2 + H 2 O
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 5-10ppm Permissible Exposure Limit Headache, dizziness, unsteadiness 50-100ppm Feeling of suffocation, nausea 100-200ppm Death from exposure in 30 to 60 minutes
Ammonia Data
NH 3 : colorless gas with a suffocating odor Hazards: Difficult to burn, LEL 15% - UEL 28% Health: extremely toxic Exposures: PEL/TWA 25ppm STEL35ppm
Effects of NH
3
0-25ppm 25ppm 50-100ppm Minor irritation of the eyes and respiratory tract PEL/TWA Swelling of the eyelids, conjunctivitis, vomiting, irritation of the throat 100-500ppm - Very dangerous concentrations, death from prolonged exposure
Carbon Dioxide Data
CO 2 : 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
400ppm -
3,000-5,000ppm -
8,000-12,000ppm -
>15,000ppm -
Effects of CO
2
Approx.. ambient level Low concentrations cause increased respiration and headaches Headache, nausea, vomiting, and if not given air or oxygen, possible unconsciousness 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. Nitrogen b. Oxygen c. Carbon dioxide d. 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 dioxide b. Nitric oxide c. Carbon monoxide d. all of the above 4. Which of the following gases is heavier than air?
a. Methane b. Acetylene c. Hydrogen Sulfide d. None of the above
Answers to Review Questions 1. 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