Chapter 5.pdf

Western Canada Mine Rescue Manual Chapter 5 Gases and Hazardous Atmospheres 5-1 OBJECTIVES Mine rescue teams will find themselves in environments where toxic and hazardous substances pose threats to their health. Being able to identify and respond safely to these substances is a fundamental aspe...

Western Canada Mine Rescue Manual Chapter 5 Gases and Hazardous Atmospheres 5-1 OBJECTIVES Mine rescue teams will find themselves in environments where toxic and hazardous substances pose threats to their health. Being able to identify and respond safely to these substances is a fundamental aspect of mine rescue. Upon completion of this chapter, the trainee shall be able to demonstrate understanding of:  Terms, concepts, and formulae  The properties and effects of mine gases Introduction Many gases found in a mine during normal operating conditions can have a harmful effect on the human body if inhaled for a period of time in concentrations above the recognized safe limit. Emergencies such as fires can emit large quantities of toxic or explosive gases and create an oxygendeficient atmosphere. The first priority for miners at the time of a mine fire is to protect themselves from these conditions. CONCEPTS AND DEFINITIONS On The Threshold of Understanding: Toxic Chemicals Deadly concentrations of toxic gases may be only a few parts per million (ppm). For many of us, 1 ppm is about as hard to visualize as the national debt. The following examples will help grasp what one part per million really represents and also help you think in metric units. One ppm is the same as:  1 metre step in 1,000 kilometres  1 millilitre per 1,000 litres of liquid  1 square centimetre in 100 square metres  1 cent in 10,000 dollars Threshold limit values (TLVs) are airborne concentrations of substances and to which most workers may be repeatedly exposed day after day without adverse effect. Because of the wide variation in individual susceptibility, however, a small percentage of people may experience discomfort from some substances at concentrations at or below the threshold limit. A smaller percentage may be affected more seriously by aggravation of a pre‑existing condition or by development of an occupational illness. The categories of TLVs are specified, as follows: Threshold Limit Value – Time Weighted Average (TLV‑TWA) is the time‑weighted average concentration for a normal eight‑hour workday and a 40‑hour workweek, to which nearly all workers may be repeatedly exposed without adverse health effects. Note: When TWA is not indicated, refer to the 8-hour TLV. A Concentration Equivalent (Ceq) formulae must be used for shifts longer than an eight‑hour workday and a 40‑hour workweek. The formula used depends on the jurisdiction in which the mine is located. 5-2 Threshold Limit Value – Short Term Exposure Limit (TLV‑STEL) is the concentration to which workers can be exposed for a short period of time without suffering from:  Irritation  Chronic or irreversible tissue damage, or  Narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue or materially reduce work efficiency, provided that the daily TLV‑TWA is not exceeded. The STEL is not a separate independent exposure limit. Rather, it supplements the time-weighted average (TWA) limit where there are recognized acute effects from a substance whose toxic effects are primarily of a chronic nature. STELs are recommended only where toxic effects have been reported from high short‑term exposures in either humans or animals. A STEL is defined as a 15‑minute exposure which should not be exceeded at any time during a work day even if the eight‑hour time‑weighted average is within the TLV. Exposures at the STEL should not be longer than 15 minutes and should not be repeated more than four times per day. There should be at least 60 minutes between successive exposures at the STEL. A period other than 15 minutes may be recommended when this is warranted by observed biological effects. Threshold Limit Value – Ceiling (TLV‑C) is the concentration that should not be exceeded during any part of the working exposure. Combined Threshold Limit Values The air in a mine may contain a combination of different gases, which when combined may cause adverse effects and therefore must be taken into account. When two or more hazardous substances have a similar toxicological effect on the same target or system, their combined effect, rather than that of either individually, should be given primary consideration. The equation for determining the combined TLV is: 𝐶1 𝐶2 𝐶𝑛 + +⋯ = 𝐷𝑜𝑠𝑒 𝑇1 𝑇2 𝑇𝑛 Where C is the concentration and T is the threshold limit value. If Dose is greater than 1, the TLV for the mixture has been exceeded. Median Lethal Dose (LD 50) refers to the dose of a toxic substance that would be fatal for 50% of a test population. Median Lethal Concentration (LC 50) refers to how concentrated a toxic substance must be in an atmosphere to be fatal for 50% of a test population. Immediately Dangerous to Life and Health (IDLH) refers to a condition posing immediate danger to life or health, or a condition posing an immediate threat of severe exposure to contaminants. If a concentration of a contaminant is above the IDLH, only positive-pressure breathing apparatus should be used to enter such an atmosphere or to move someone through that atmosphere. 5-3 Airborne particulate concentrations are generally measured in milligrams per cubic metre of air (mg/m3) and gaseous concentrations are measured as parts per million or % by volume. Lower and Upper Explosive Limits refer to the minimum (LEL) and maximum (UEL) concentrations of a gas or vapour in air that will ignite when exposed to an ignition source provided there is sufficient oxygen to support combustion. Relative density (vapour density or specific gravity) is the ratio of the density of a substance to the density of a standard substance under specified conditions. For liquids and solids the standard is usually water. For gases the standard is often air. Fig 5.1 Relative density and Explosive range for Methane The pH scale is a means of measuring a substance’s acidity or alkalinity. The scale is broken down into 14 degrees. Pure water has a pH of 7. A pH below 7 indicates that a substance is acidic, while a pH above 7 indicates that a substance is basic or alkaline. Both acidic and basic substances are corrosive, but the severity increases the further away one gets from a pH of 7. Regulatory requirements and site-specific procedures dictate special precautions required for any gases stored or transported in pressurized containers. 5-4 NAME OF GAS Air Gas Mixture (AIR) PROPERTIES Air is colourless, odourless, tasteless and non-flammable. It is a mixture of several gases that, though ordinarily invisible, can be weighed, compressed to a liquid or frozen to a solid. Pure, dry air at sea level contains several gases, in the following proportions by volume %: nitrogen (N2), 78.09; oxygen (O2), 20.94; argon (Ar), 0.94 and carbon dioxide (CO2), 0.03. Traces of other gases, such as hydrogen and helium, are also present. The air in a well ventilated mine seldom shows any depletion of the oxygen content. HOW FORMED Air is the invisible envelope surrounding the earth, in which plants, animals, and human beings live and breathe. Gases in Air 20.94 % 0.03% 78.09 % 0.94% Nitrogen Oxygen Carbon Dioxide Argon EFFECTS ON HUMANS Mine air may be contaminated by the presence of other gases such as carbon monoxide, sulphur dioxide, hydrogen sulphide, methane, oxides of nitrogen and excess carbon dioxide. The presence of these gases may be due to any of the following:  Blasting or other explosions  Mine fires  Diffusion from ore or country rock, as with methane or radon  Decay of mine timber  Absorption of oxygen by water or oxidation of timber or ore  Use of diesel motors underground  Gas released from thermal water – carbon dioxide, hydrogen sulphide Except in the case of fire, adequate positive ventilating currents will prevent any dangerous accumulation of these gases. Gases may affect people either by their combustible, explosive or toxic properties, or, if inert, by the displacement of oxygen. The effects may be due to a variety of conditions including:    Altitude: Breathing becomes more laborious due to the decrease in oxygen content as the altitude increases. This is not dangerous unless conditions are extreme or the work arduous. Humidity: High temperatures with high humidity are very enervating and cause considerable discomfort. Temperature: High temperatures with low humidity are not dangerous except from the blistering effect of heat. Impure Air Non-toxic gaseous impurities are not dangerous unless they have displaced oxygen to a level below 19.5%. Regardless of the oxygen level, some toxic gases have deadly effects, even in very low concentrations. Effects may be sudden or gradual, depending on the concentration of the impurity. 5-5 NOTE: The Physiological Effects charts included with each gas sheet are general levels associated with the effects, not specific ranges. The data contained comes from many different resource materials. Care has been taken to use the most consistent and recent data possible. NAME OF GAS and CHEMICAL SYMBOL Acetylene (C₂H₂) PROPERTIES: Acetylene is colourless, has a faint odour of ether, and is tasteless. Acetylene is a highly flammable hydrocarbon fuel that produces industry’s hottest flame (3,260 C/5,900 F) when combined with oxygen in the oxyacetylene process. Acetylene is very unstable and can become dangerously explosive if compressed above 100 kilopascals (kPa) (15 psi) in the free state. Acetylene cylinders are therefore packed with porous material that is saturated with acetone in which the acetylene is dissolved. Acetylene can thus be safely stored and transported at a pressure of 1,700 kPa (250 psi). Never use acetylene above 100 kPa (15 psi). Acetylene has an explosive range of 2.8%–81%. HOW FORMED Product of mixing water with calcium carbide EFFECTS ON HUMANS Can displace oxygen OTHER INFORMATION Acetylene forms an explosive compound with copper and alloys containing more than 67% copper. The hazard is carefully avoided in the manufacture of welding torches, tips, and regulators. If an acetylene cylinder has been laid on its side, place the cylinder upright and wait at least one hour before using, as per the Canadian Centre for Occupational Health and Safety. Some welders call acetylene “gas” and oxygen “air”. This dangerous habit could cause death or injury under certain circumstances. Call all gases by their proper names. 5-6 NAME OF GAS and CHEMICAL SYMBOL Ammonia (NH₃) PROPERTIES Ammonia is colourless, has a very pungent odour characteristic of drying urine, and is tasteless. Ammonia (also known as anhydrous ammonia or ammoniac) is a flammable caustic gas with a strong and distinctive smell detectable at concentrations of 1 to 50 ppm. Ammonia has an explosive range of 16%–25%. HOW FORMED It is formed by the reaction of nitrogen with hydrogen in the presence of a catalyst. It is stored in commercial cylinders as a compressed liquefied gas. It is corrosive and also explosive when exposed to heat and oxidizing substances. It can also be formed by contact between ammonium nitrate and cement. EFFECTS ON HUMANS Ammonia’s corrosive qualities will irritate the eyes, nose, throat, lungs, or moist skin and may cause considerable distress. Even brief exposure to concentrations of 5,000 ppm or more may cause rapid death due to suffocation or oedema in the lungs. OTHER INFORMATION: Specific clean‑up procedures:  Move the leaking cylinder to an exhaust hood or safe outdoor area for venting. Mark the empty cylinder DEFECTIVE.  Use a water spray or fog to reduce the gas cloud from a serious leak or spill, but do not aim a water jet directly at the source of the leak.  If possible, turn the leaking cylinder so that gas rather than liquid escapes. Isolate the area until the gas has dispersed. Firefighting procedures for fires involving ammonia: Carbon dioxide and powder extinguishers are suitable for fighting fires in which ammonia is involved. Stop the flow of gas or liquid and move ammonia cylinders from the fire area if it is safe to do so. Use a water spray to keep containers cool but do not direct water at the source of an ammonia leak or a venting safety device. Pressurized containers may explode in a fire, releasing irritating ammonia gas; be prepared by wearing self‑contained breathing apparatus. Ammonia is not readily ignited, but explosions of air-ammonia mixtures have occurred, particularly in confined spaces. Physiological Effects of Ammonia NH₃ in the Atmosphere (PPM) Symptoms >1 Detectable odor 1–3 Mild irritation of mucus membranes 5–15 Moderate irritation of mucus membranes 30 Chest pain, shortness of breath, coughing 40–60 Fluid in the lungs (oedema), pneumonitis 400 Fatal in 30 minutes 1,000 Fatal in a few minutes 5-7 NAME OF GAS and CHEMICAL SYMBOL Carbon Dioxide (CO₂) PROPERTIES Carbon dioxide is a colourless, odourless gas that when breathed in large quantities may cause a distinctly acidic taste. The gas will not burn or support combustion. Carbon dioxide is heavier than air and is often found in low places and abandoned mine workings. HOW FORMED Carbon dioxide, an inert gas, is a normal constituent of mine air. It is a product of the decomposition or combustion of organic compounds in the presence of oxygen as well as respiration of humans and animals. The proportion of carbon dioxide in mine air is increased by the process of breathing, by open flame, explosions and blasting, or by escape from thermal water. It is also used as an extinguishing agent and is also released from dry ice. EFFECTS ON HUMANS Clinical investigations indicate that carbon dioxide influences the respiratory rate. This rate increases rapidly with increasing amounts of carbon dioxide. Physiological Effects of Carbon Dioxide CO₂ in the Atmosphere (ppm) Increase in respiration 500 Slight 20,000 50% 30,000 100% 50,000 300% & Laborious 100,000 Survivable for only a few minutes 5-8 NAME OF GAS and CHEMICAL SYMBOL Carbon Monoxide (CO) PROPERTIES Carbon monoxide is a colourless, odourless, tasteless gas that, when breathed in even low concentrations, will produce symptoms of poisoning. Carbon monoxide has an explosive range of 12.5%–74%. It is only slightly soluble in water and is not removed from the air to any extent by water sprays. It is slightly lighter than air. HOW FORMED Carbon monoxide gas is one of the greatest chemical hazards to humans. It is a product of combustion in normal blasting operations and the operation of internal combustion engines. It is also produced by occurrences such as mine fires or gas explosions. It can be formed wherever organic compounds are burned in an atmosphere with insufficient oxygen to carry the process of burning or oxidation to completion. EFFECTS ON HUMANS When carbon monoxide is absorbed it reduces the capacity of the haemoglobin for carrying oxygen to the tissues. The affinity of haemoglobin for carbon monoxide is about 300 times its affinity for oxygen. This means that when even a small amount of carbon monoxide is present in the air breathed, the haemoglobin will absorb the carbon monoxide in preference to the oxygen. It is this interference with the oxygen supply to the body that produces the symptoms of poisoning. Physiological Effects of Carbon Monoxide CO in the Atmosphere (PPM) Symptoms 0–35 No symptoms 36–200 Flu-like symptoms: runny nose, headache 201–800 Dizziness, drowsiness, vomiting in less than an hour 801+ Unconsciousness, brain damage, and death 5-9 NAME OF GAS and CHEMICAL SYMBOL Chlorine (Cl₂) PROPERTIES Chlorine is a heavy, greenish yellow, non-flammable gas that has an odour similar to chlorine bleach and is tasteless. Chlorine is easily liquefied and is supplied commercially as a liquid under pressure in cylinders and larger containers. HOW FORMED Electrolysis of common salt and other chemical reactions involving chlorine compounds. Some of its uses include treating potable water and milling processes. EFFECTS ON HUMANS Because of its fairly low solubility in water, chlorine is a severe irritant to the eyes, skin, and respiratory system (oedema). OTHER INFORMATION Chlorine itself is not flammable, but it may react to cause fire or explosions upon contact with turpentine, ether, ammonia, hydrocarbons, hydrogen, or steel pipes and vessels. Refer to site-specific procedures for handling and storing chlorine. Only specially trained workers should manage incidents involving chlorine. Special considerations for handling leaking chlorine containers:  If chlorine is escaping as a liquid, turn the container so that chlorine gas escapes. The amount of gas escaping from a leak is about one‑fifteenth the amount of liquid which will escape through a hole of the same size.  Do not apply water to a chlorine leak.  Pinhole leaks in cylinders and large containers may sometimes be temporarily stopped by tapered hardwood pegs or metal drift pins driven into the holes. First turn the container so that only gas is escaping. Use extreme care in driving the plug because the wall area surrounding the hole may be thin and crumble. After taking this emergency measure, empty the cylinder as quickly as possible. Physiological Effects of Chlorine Gas Cl₂ in the Atmosphere (PPM) Symptoms 0–6 Eye irritation 7–15 Throat and lung irritation 16–30 Chest pain, vomiting, coughing, difficulty breathing, excess fluid in lungs (oedema) 430+ Fatal in 30 minutes 5-10 NAME OF GAS and CHEMICAL SYMBOL Hydrogen (H₂) PROPERTIES Hydrogen is a colourless, odourless and tasteless gas. It is highly flammable. Hydrogen has an explosive range of 4%–74% with as little as 5% oxygen in the air. HOW FORMED Hydrogen can be produced when rock is heated to incandescence. It is a product of incomplete combustion or distilling coal. The most common source of hydrogen at mines is battery charging. EFFECTS ON HUMANS Hydrogen may cause an oxygen-deficient atmosphere resulting in asphyxiation. 5-11 NAME OF GAS and CHEMICAL SYMBOL: Hydrogen Cyanide (HCN) PROPERTIES Hydrogen cyanide is a colourless, tasteless gas with a distinctive odour of bitter almonds. Many people cannot detect presence by odour therefore the scent alone does not provide adequate warning of hazardous concentration. It condenses to a colourless liquid at temperatures below ‑26 C. Hydrogen cyanide has an explosive range of 5.6%–40%. HOW FORMED Hydrogen cyanide is formed by the reaction of hydrochloric acid on cyanide compounds, such as potassium/sodium cyanide. It may occur in concentrator areas where cyanide is used as a reagent in the milling of gold ore, and other places where cyanide compounds are used. It may also be released from cyanide-bearing concentrator tailings. A solution of hydrogen cyanide in water is called hydrocyanic acid or prussic acid. EFFECTS ON HUMANS Hydrogen cyanide is a fast‑acting and deadly poison that causes paralysis of the respiratory system and chemical asphyxiation. It interferes with the normal use of oxygen by nearly every organ of the body. It is particularly dangerous as it can be absorbed through the skin as well as by inhalation. HCN in the Atmosphere (PPM) 0–20 20–50 >50 >110 Physiological Effects of Hydrogen Cyanide Symptoms of Exposure May detect odour. Minor symptoms. Depending on amount and exposure time, may have initially experience restlessness and increased respiratory rate. Other early symptoms may include weakness, giddiness difficulty breathing, heart palpitations, headache. Onset of signs and symptoms is usually rapid after inhalation and may continue for several hours after exposure Immediately dangerous to life and health (IDLH). Symptoms include nausea, vomiting, convulsions, respiratory failure, unconsciousness. Can be quickly fatal 5-12 NAME OF GAS and CHEMICAL SYMBOL Hydrogen Sulphide (H₂S) PROPERTIES Hydrogen sulphide is colourless, tasteless, highly toxic, and highly soluble in water. In low concentrations its distinctive rotten‑egg smell is noticeable, but in high concentrations the sense of smell is quickly paralyzed by the action of the gas on the respiratory system and cannot be relied upon as a warning. Hydrogen sulphide has an explosive range of 4.3%–45%. HOW FORMED Dust explosions occurring in blasting operations in sulphide ore bodies can create hydrogen sulphide. It is also formed from burning sulphide ores or in the reaction of hydrochloric acid on sulphide concentrations. It may also be released from coal or country rock pockets, or from vegetable matter decomposing in water. EFFECTS ON HUMANS Hydrogen sulphide is highly toxic and has neurotoxic effects. It immediately paralyzes the sense of smell and progresses to respiratory paralysis then death. It is an irritant that may cause pulmonary oedema. Physiological Effects of Hydrogen Sulphide H₂S in the Atmosphere (PPM) Effects of Exposure <1 Odour (rotten egg) can be detected 10 No known adverse health effects; respiratory protection required above this limit 20–50 Eye, nose, throat, and lung irritation 50–100 Prolonged exposure can cause a runny nose, cough, ( hoarseness, and shortness of breath >100 Immediately dangerous to life and health (IDLH) 5-13 NAME OF GAS and SYMBOL MAPP – Mixture of Methylacetylene, Propadiene, Propylene, Propane PROPERTIES MAPP is colourless, tasteless, slightly soluble in water and may smell slightly fishy. MAPP has all the best features of acetylene, natural gas and propane, and is extremely safe to use. It is a very stable gas. MAPP has an explosive range of 1.8%–11.7%. HOW FORMED Man-made combination of gases stored as a liquid under pressure. EFFECTS ON HUMANS MAPP may cause an oxygen deficient atmosphere and in high concentrations may have an anaesthetizing effect. MAPP is a slight irritant to the skin and, due to its high evaporation rate, may cause tissue freezing or frostbite on skin contact with the liquid. 5-14 NAME OF GAS and CHEMICAL SYMBOL: Methane (CH₄) PROPERTIES Methane is a colourless, odourless and tasteless gas. An odour caused by the presence of other gases such as hydrogen sulphide often accompanies it. Methane is lighter than air and has an explosive range of 5%–15%. Guidelines for methane in work environments:  ≥1% methane (20% of the LEL): No blasting or shot firing.  ≥1.25% methane (25% of the LEL): Isolate electrical circuits.  ≥2.5% methane (50% of the LEL): All workers are withdrawn from any work. HOW FORMED It is formed by the decomposition of organic matter in the presence of water and the absence of oxygen. It may be seen as bubbles in pools of water. It is a component of natural gas. Methane gas may be trapped in hardrock and released through diamond drilling operations. Methane is also produced by decaying timber. EFFECTS ON HUMANS Methane may cause an oxygen-deficient atmosphere resulting in asphyxiation. 5-15 NAME OF GAS and CHEMICAL SYMBOL Nitrogen (N₂) PROPERTIES Nitrogen is a colourless, odourless, tasteless and inert gas. HOW FORMED Nitrogen is a naturally occurring constituent of the atmosphere. It is used in industry in either liquid or compressed gas form. EFFECTS ON HUMANS Nitrogen itself has no physiological effect on humans. However, increased nitrogen levels may cause an oxygen-deficient atmosphere resulting in asphyxiation. 5-16 NAME OF GAS and CHEMICAL SYMBOL Nitrogen Dioxide (NO₂) PROPERTIES No colour in small concentrations, reddish brown in high concentrations. May smell like blasting fumes. Acidic taste if inhaled in high concentrations. It is one of many oxides of nitrogen. HOW FORMED Nitrogen dioxide is formed when nitric oxide (NO) is exposed to air, such as in electric arcing, oxy-gas welding, internal combustion engines, and burning or detonating explosives. EFFECTS ON HUMANS Nitrogen dioxide corrodes the respiratory passages and inhaling relatively small quantities may cause death. Symptoms from low doses of nitrogen dioxide may have a delayed onset. Its effects on the respiratory passages include oedema and swelling. This irritation may be followed by bronchitis or pneumonia, with potentially fatal results. Physiological Effects of Nitrogen Dioxide NO₂ in the Atmosphere (PPM) 60 100 100–150 200–700 Effects of Exposure Minimum causing immediate throat irritation Minimum causing coughing Dangerous for even short exposure Quickly fatal after short exposure 5-17 NAME OF GAS and CHEMICAL SYMBOL Oxygen (O₂) PROPERTIES Oxygen is a colourless, odourless and tasteless gas. It is required to support life and combustion. HOW FORMED Found in the atmosphere as a product of photosynthesis. EFFECTS ON HUMANS Any reduction from normal oxygen levels affects human physiology. Increased levels of oxygen reduce fatigue, but may have other effects over long periods of time that could occur with the use of an oxygen breathing apparatus. Atmospheres in the workplace should contain at least 19.5% oxygen. Physiological Effects of Oxygen Deficiency % O₂ in the Atmosphere Effects of Exposure (PPM) >23 (230,000) Will accelerate combustion 21 (210,000) Normal breathing 17 (170,000) Breathing faster and deeper 15 (150,000) Dizziness, buzzing noise, rapid pulse, headache, blurred vision. 9 (90,000) May faint or become unconscious. 6 (60,000) Movement convulsive, breathing stops. Shortly afterwards, the heart stops. 5-18 NAME OF GAS and CHEMICAL SYMBOL Propane (C₃H₈) PROPERTIES Propane is colourless, odourless but commercially scented, tasteless, and flammable. Propane is a liquefied petroleum gas. Propane vapour is heavier than air. Any escaping gas will seek out low places, such as excavations, which may result in the accumulation and creation of flammable mixtures. Propane has an explosive range of 2.4%–9.5%. HOW FORMED Propane is extracted from natural and refinery gases. It is compressed into a liquid state and will remain as a liquid when stored under pressure. EFFECTS ON HUMANS Propane may cause an oxygen-deficient atmosphere resulting in asphyxiation. OTHER INFORMATION When converting to vapour, liquid propane will expand to about 270 times its liquid volume. Therefore, escaping liquid gas is more dangerous than vapour escaping from a leak of the same size. 5-19 NAME OF GAS and CHEMICAL SYMBOL Sulphur Dioxide (SO₂) PROPERTIES Sulphur dioxide is colourless, has an acidic taste and has a strong sulphurous smell with a low odour threshold. Sulphur dioxide is soluble in water. It is a heavy gas and will accumulate in low places. HOW FORMED Sulphur dioxide is a gas produced by heating, burning, or blasting sulphide ores. It is also produced in explosions of sulphide ore dust. Some diesel fuels also produce low amounts of sulphur dioxide when burned. EFFECTS ON HUMANS Sulphur dioxide may cause noxious effects before it becomes toxic. Irritation of the respiratory tract and lungs will cause oedema. Physiological Effects of Sulphur Dioxide Exposure Concentrations of SO₂ in the Atmosphere (PPM) 0 – 0.25 > 0.25 >100 ppm Effects of Exposure Mild to severe irritation to eyes, nose and throat Sulphur dioxide can cause a life-threatening condition from accumulation of fluid in the lungs (pulmonary oedema). Exposure to high concentrations can cause coughing, nausea, vomiting, shortness of breath, tightness in chest, stomach pain and corrosive damage to the airways and lungs (symptoms may be delayed). May cause long term respiratory effects. Skin contact may cause burns, but signs and symptoms may vary (e.g., stinging pain, redness of the skin and blisters). Contact with eyes can cause mild irritation to severe burns. Immediately dangerous to life and health (IDLH) 5-20 ATMOSPHERIC HAZARDS DURING AND AFTER FIRES During and following fires, the two greatest hazards to life are carbon monoxide poisoning and oxygen deficiency. The conditions that cause contamination of mine atmospheres are as follows, listed in order of the seriousness of the hazard:  Carbon monoxide: This gas is always present at the time of a fire and gives little or no warning of its presence.  Oxygen deficiency: This condition occurs when oxygen is consumed by combustion or chemical reaction and is replaced by toxic or inert gases. Precautions must always be taken against it.  Explosive gases and smoke: Irritating qualities and obstructs vision  Methane: This gas is not produced by mine fires or explosions but may cause them. Its presence in a mine during rescue or recovery operations creates a major hazard.  Sulphur Dioxide: This gas is present when a fire occurs in a sulphide ore body. Because of its irritating qualities, it may give advance warning in low concentrations.  Other gases: Hydrogen sulphide, nitrous oxides, hydrogen cyanide, etc., are not likely to be encountered but the possibility of their occurrence should be kept in mind. Hydrogen sulphide sometimes indicates the presence of methane. Burning Conveyor Belts and Rubber Tires Polyvinylchloride (PVC)-covered belting is practically non-flammable, but when heated, PVC, synthetic rubber, and neoprene (found in rubber tires) give off chlorine gas. Other gases produced by burning rubber are listed below. GASES PRODUCED BY BURNING RUBBER, NEOPRENE AND PVC Carbon Monoxide Chlorine Hydrogen Chloride Phosgene Sulphur Dioxide Hydrogen Sulphide Nitrogen Dioxide Ammonia Hydrogen Cyanide Arsine Phosphine Radiation Sources One source of radiation is nuclear gauges used for measuring. When responding to an incident involving this source, contact the site Radiation Safety Officer (RSO). Another source of radiation is radon, a naturally occurring element released into the mine’s atmosphere. As it is released, it continues to decay and forms airborne radioactive atoms. If radon levels in an area are very high, breathing protection may be required to reduce radiation exposure. Refer to site-specific safety procedures for all radiation emissions. 5-21 MINE RESCUE GAS CHART – For General Reference Only (non-regulatory) Lighter Than Air Substance Chem. Symbol Relative Density Air = 1 Explosive Range % T.L.V. ACGIH I.D.L.H. NIOSH Properties COT = Colourless, Odourless, Tasteless How Formed (See individual gas sheet for further information) Hydrogen H2 0.07 4–74 Asphyxiant COT Methane CH4 0.55 5–15 YES Not Listed Not Listed Ammonia NH3 0.60 16–25 YES YES Acetylene C2H2 0.91 2.8–81 Asphyxiant Not Listed Colourless, Strong odour Colourless, Distinct odour Incomplete comb. electrolysis of water, battery charging Decomposition of organic matter, carbonaceous rock, decaying timber, component of natural gas Reaction of nitrogen & hydrogen in the presence of a catalyst Water on calcium carbide Hydrogen Cyanide HCN 0.94 5.6–40 YES YES Colourless, Bitter Almond odour Carbon Monoxide Nitrogen CO 0.97 12.5–74 YES YES COT N2 0.97 N/A Asphyxiant Not Listed COT 1.00 N/A AIR Heavier Than Air COT Acid on sodium or potassium cyanide, produced during heat treating of drill steel, may be released from tailings where cyanide was used for mineral recovery Fires, gas explosions, blasting, incomplete combustion, diesel and gas engine exhaust Constituent of air, Commercial liquid or gas Nitrogen 78.09 %, Oxygen 20.94%, Carbon Dioxide 0.03%, Argon & Other Gasses 0.94% Oxygen O2 1.10 N/A N/A Hydrogen Sulphide H2S 1.19 4.3–45 YES Not Listed YES COT Carbon Dioxide CO2 1.53 N/A YES YES COT, Taste in high concentration Propane C3H8 1.56 2.4–9.5 YES Not Listed MAPP N/A 1.58 1.8–11.7 N/A Sulphur Dioxide Chlorine SO2 2.20 N/A YES Not Listed YES Cl2 2.49 N/A YES YES COT Commercially Scented Distinct fishy Odour Colourless, Sulphur smell, Acid taste Green yellow, Bleach smell Nitrogen Dioxide NO2 2.62 N/A YES YES Colourless, Rotten Egg Odour Colourless to redden brown, Acid taste in high concentration Constituent of air, From photosynthesis Decomposition of some sulphur compounds, blasting sulphide ores, decomposition of vegetable matter in water, hydrochloric acid on sulphide Constituent of air, breathing of humans & animals, decomposition or combustion of organic compounds with presence of oxygen Petroleum distillate Commercially manufactured Heating, burning or blasting sulphide ores, burning of some diesel fuels Principally from electrolysis of salt One of the many oxides of nitrogen, associated with burning & blasting, arching, welding, diesel exhaust Fig 5.1 General gas information for most commonly encountered gases 5-22