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Primer on H2S

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  • Author: Gordon M. Groat – Consulting ScientistLeduc Number 1 Energy Discovery Centre#6, 20 Haven AvenueDevon, Alberta T9G 2B9Open Source // Public DistributionGrant funding by:Government of AlbertaDepartment of Energy
  • We all know sulphur is used in matches.... But it has many uses you may not be familiar with.
  • This is a photo of a loading facility in Vancouver, the yellow pile is sulphur. Canada produces about 25% of the World supply of sulphur. Canada is one of the world's leading producers of sulphur and a global leader in the technologies for safely handling and developing the resource. Elemental sulphur when contained in natural gas is referred to as sour gas. Sour gas makes up about 21% of Alberta’s natural gas reserves; the province also accounts for nearly 85 per cent of Canada's sour gas production. British Columbia's natural gas industry contributes most of the remainder of Canada's sour gas. There are over 6,000 sour gas wells and 18,000 kilometres of operating sour gas pipelines in Alberta.  Sour gas is processed at approximately 250 plants in Alberta, including more than 50 larger facilities that produce elemental sulphur. In this way, sulphur is removed from the sour gas. The result is sweet natural gas.
  • Sulphur is usually a precursor to other chemicals like sulfuric acid (H2SO4)Elemental sulphur is used in fertilizers, paper, pharmaceuticals, steel, and other products. Alberta is the largest exporter of sulphur in the WorldVulcanization of rubberGunpowderDetergentsPhotographyBleaches PaperPreservative for dry fruitCellophaneRayonIndustrial activities such as food processingCoke ovensKraft paper millsRayon textile manufacturingTar and asphalt manufacturing plants TanneriesRefineries
  • In addition to existing in natural gas, H2S can be found in sour crude oil, sulphur hot springs, sewage, swamps, manure piles in stockyards, landfills, and the holds of fishing ships, as well as in the processing of leather, pulp and paper, and rayon textiles.  Sour gas deposits are found in several regions throughout Alberta, with the majority in central and western Alberta.    How is sour gas formed?Hydrogen sulphide occurs naturally in crude petroleum, volcanic gases, and hot springs.  It can also form when organic materials, such as plants or human and animal wastes decompose in an oxygen-free environment, a process known as anaerobic decomposition. This process can occur in sewers, manure piles, swamps, and composts.
  • In addition to existing in natural gas, H 2 S can be found in sour crude oil, sulphur hot springs, sewage, swamps, manure piles in stockyards, landfills, and the holds of fishing ships, as well as in the processing of leather, pulp and paper, and rayon textiles.  Sour gas deposits are found in several regions throughout Alberta, with the majority in central and western Alberta.   
  • The misconception people have is that because a well has a certain percentage of H2S that they will be exposed to that percentage. Not true. Due to lease setbacks and a myriad of other safety precautions, the “ppm” or the atmospheric exposure (what we breathe) is a totally different number. Remember... It’s measured in parts per million or ppm – gas dissipates into the atmosphere and is then measured in ppm.It is, however, dangerous for rig crews and people on sour gas drilling sites, for this reason the areas are monitored with air sensing equipment plus special sensory units each person has with them at all times on site. These workers all have available self contained breathing units or “air masks” they can put on in order to remain on site to make repairs or to evacuate to a safe zone outside of the setback area. Setbacks are designed for the designated purpose of keeping the public safe.
  • Percentage of H2S is not ppm – leveraging meteorological data, flow rates, and percentages of hydrogen sulphide, areas of exposure are determined and setbacks are designed accordingly. Based on flow rate, chemical compounds (percentage of H2S), this data is then modelled with at least 5 years of meteorological data, a standard that was set at 43,800 hours of data that analyzes wind, direction, speed, temperatures, and a variety of other criteria. Through these criteria, dispersion zones are created and determing where risk exists informs setback requirements and, in the event there is a population nearby, where evacuation zones would be required.
  • When the evacuation zone is reached, i.e. the area where a specific level of H2S exists, while safe for human exposure, it will be ignited in insure H2S does not present a danger to nearby residents.
  • Parts Per Million (ppm) is how we measure what’s in the air we breathe. H2S health and safety standards are designed around ppm exposure.
  • The Provincial Advisory Committee on Public Safety and Sour Gas (PSSG) was formed in 2000 to address concerns raised about sour gas.  The committee released their final report at the end of 2000, including 87 recommendations for the development of sour gas. Continuous developments and refinements regarding the management, modeling, and development of safety policies. The ERCB (Energy Resources Conservation Board) regulates public safety where sour gas is concerned.Some of the things you will find regarding sour gas wells include;Strict engineering standards are applied to equipment that will be deployed on a sour gas well. Crews are trained on live wells @ Nisku Training SiteAll Drillers and Rig Managers are trained and must pass certification testsLease hands and roughnecks are also trained on blowout prevention and sour gas, they have certifications alsoMSDS stands for Material Safety Data Sheet – this contains hazard handling techniques and the scientific properties of a chemical.
  • Alberta Sour Gas Wells Stats Source: Government of Alberta, 2007http://alberta.ca/home/NewsFrame.cfm?ReleaseID=/acn/200706/21611073FD84A-F7AA-436E-9961F7227A1CDCB8.html
  • Operators of "critical sour wells"– those thought to pose the greatest risks to the public–must install redundant safety equipment, prepare detailed emergency-response plans, go door to door to warn residents of impending drilling and maintain certain setback distances from homes and public buildings. In the event of a release, evacuation of the surrounding area becomes mandatory if the hydrogen sulphide concentration reaches 20 parts per million. Before Lodgepole, there was no standard.
  • ERCB requires applicants to have specific size lease setbacks from dwellings in order to maintain the safety and ability of any potential H2S to dissipate to levels that do not cause danger to humans. In the event a problem occurs, evacuation procedures are in place to insure public safety.
  • NACE (National Association of Corrosion Engineers)NACE was established in 1943 and has grown from the original 11 engineers to more than 20,000 members in over 100 countries. NACE International is involved in every industry and area of corrosion prevention and control, from chemical processing and water systems, to transportation and infrastructure protection.Electro-re-smelting and chemical additive management of drilling fluids are combined with special handling requirements for drill pipe corrosion inhibitors.http://www.nace.org/content.cfm?parentid=1005&currentID=1005
  • Smart pigs check for corrosion to maintain pipeline integrity.
  • This blowout preventer a.k.a. BOP is mandatory equipment when drilling a well. It has three RAMS, each of which can prevent a blowout. This is a redundant safety system used everywhere in Canada and the rest of the World. A BOP is a set of two or more BOPs used to ensure pressure control of a well. A typical stack might consist of one to six ram-type preventers and, optionally, one or two annular-type preventers. A typical stack configuration has the ram preventers on the bottom and the annular preventers at the top. The configuration of the stack preventers is optimized to provide maximum pressure integrity, safety and flexibility in the event of a well control incident. For example, in a multiple ram configuration, one set of rams might be fitted to close on 5-in. Diameter drillpipe, another set configured for 4 1/2-in. drillpipe, a third fitted with blind rams to close on the openhole and a fourth fitted with a shear ram that can cut and hang-off the drillpipe as a last resort. It is common to have an annular preventer or two on the top of the stack since annulars can be closed over a wide range of tubular sizes and the openhole, but are typically not rated for pressures as high as ram preventers. The BOP stack also includes various spools, adapters and piping outlets to permit the circulation of wellbore fluids under pressure in the event of a well control incident. Annular RamsUsed in conjunction with hydraulic control system, the annular BOP seals off the annulus of different sizes when drilling tool is set in the hole, when there is no drilling tool in the hole, it can also seal off the well head. If well blowout happens during the coring and measuring operation, it can seal off the annular spaces between the well barrel and kelly, coring tool, cable and steel rope etc. matched with pressure-relief valve and buffer tank, it can force-execute the running/retrieving drill operations through butt-weld drilling-rod at 18 degree without fine thread.
  • The float valve is a mechanism designed to fill without overflowing, it is an additional protective measure inside a BOP stack.
  • Flaring burns the H2S – any well that becomes “wild” – such as the Lodgepole blowout, is supposed to be flared. The changes the H2S to sulphur dioxide.
  • 0.0047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of hydrogen sulfide, normally described as resembling "a rotten egg".10 ppm has an exposure limit of 8 hours per day.10-20 ppm is the borderline concentration for eye irritation.0-100 ppm leads to eye damage.150-250 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger,320-530 ppm leads to pulmonary edema with the possibility of death.530-1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing; 800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure (LC50 a.k.a. Lethal Concentration 50%) with the 50% signifying the concentration required to be lethal to 50% of a population.1000 ppm may cause immediate collapse with loss of breathing, even after inhalation of a single breath.H2S is toxic to humans and animals at very low concentrations.  At concentrations between 10 - 750 ppm H2S becomes increasingly toxic.  It is deadly to humans in concentrations of greater than 750 ppm. Most people can smell the distinctive 'rotten eggs' odour of the gas at concentrations between 0.1 and 0.3 ppm.  At concentrations of 20 ppm or more, people may begin to experience slight discomfort in the eyes and nasal passages, and workers are required to wear breathing apparatus.  At higher levels, around 100 ppm, the gas becomes more dangerous because it quickly numbs the sense of smell.  Health effects such as dizziness and slight respiratory difficulties begin with exposure for an hour at 150 ppm, and fatalities can result from exposure to levels above 750 ppm unless the person is immediately evacuated and resuscitated.
  • In Alberta, workers are exposed to hydrogen sulphide most often during drilling and production of natural gas, crude oil and petroleum products. Hydrogen sulphide can accumulate in sewers, sewage treatment plants, liquid manure plants, or hide storage pits in the tanning industry. Well drillers, tunnel workers and miners may be exposed when underground pockets of hydrogen sulphide are encountered. Hydrogen sulphide is also a raw material used to manufacture inorganic sulphides, sulphuric acid and thiols (also known as mercaptans). Government of Alberta Employment and Immigration http://employment.alberta.ca/documents/WHS/WHS-PUB_ch029.pdf
  • In terms of public safety, however, the defining moment came at 2:30 p.m. on Oct. 17, 1982, when an Amoco well blew out 12 miles west of the small town of Lodgepole. Two workers from Texas were killed, and sour gas spurted from the well for 67 days. Nauseating odors reached Edmonton, 75 miles away; people closer to the blowout reported headaches, eye irritation, nosebleeds among children and various gastrointestinal and respiratory ailments. After a high-profile inquiry, the Alberta Energy Resources Conservation Board (now the Energy Utilities Board) concluded in 1984 that the accident "could probably have been avoided, even allowing for equipment failures, if Amoco had followed a policy of cautious drilling in the critical zone and if Amoco had been better prepared to deal with unexpected developments. The public was understandably concerned, frightened and angry about the blowout." Wells where the concentration of hydrogen sulphide in the gas exceeds 5% and the gas contains high volumes of condensate are considered "critical sour wells"; therefore, special precautions must be taken. These precautions include, amongst other things, a more comprehensive monitoring and inspection plan, and an accident contingency plan. As will be discussed in Parts II and III, procedures now call for ignition of the well once it is considered "wild". The scientific debate continues as to the safe exposure limits for hydrogen sulphide. The summary and recommendations report for the Lodgepole Blowout states: "The protection plan was designed to ensure that if an H2S concentration of 15 parts per million (ppm) was reached in any area where people were residing, then they would leave the area. Additional standards were identified for persons described as "sensitive", which generally was taken to mean persons with respiratory problems, very young children, the elderly, and pregnant women. However, for various reasons, these additional standards, while acknowledged, were not actually applied.The monitoring data gathered during the event shows that the dispersion of the gas cloud from the well was actually quite rapid, notwithstanding the large volumes of H2S gas being emitted. For example, no concentrations in excess oí 10 ppm were found at any residences located farther than 20 km from the well, and there were only a few instances inside that 20 km radius. The highest concentration recorded at Cynthia was 10 ppm, at Lodgepole 14.5 ppm, and 5 ppm at Drayton Valley, some 45 km from the well. The highest reading in Edmonton was 0.5 ppm.
  • Complete chemical breakdown available at:http://albertatravel.org/Miette_Hotsprings2.htm
  • In 1982, Amoco was drilling a sour gas well, which blew wild. Especially because the company had experienced a serious blowout in the same gas field five years earlier, regulatory and public backlash was intense. Much of the public outrage occurred because, on some days, the rotten-egg odour of hydrogen sulfide in the gas could be smelled as far away as Winnipeg, nearly 1,500 kilometres distant. Edmonton reported foul smelling odour and is about 130 km away.Town of Cynthia, 20 Km from lodgepole, reached 13 ppm.Sour gas flowed at an estimated rate of 150 million cubic feet (4,200,000 m3) per day. The H2S content of the gas was 28 per cent, and the well also produced 20 thousand barrels per day (3,200 m3/d) of sulfur-contaminated, orange-coloured condensate. The well was out of control for 68 days, during 23 of which the well was not ignited. During that time hydrogen sulfide from the blowout took the lives of two blowout specialists and sent another 16 people to hospital. Today, operators are required to ignite the well quickly in the event of a major sour gas blowout. This eliminates the dangers of highly toxic hydrogen sulfide in the air.When the crew ignited the well, the fire destroyed the Nabors 14E rig (worth about $8 million) in nine minutes; it also scorched 400 acres (1.6 km2) of forest. Amoco's direct costs to bring the well under control were approximately $20 million. Huge amounts of natural gas, natural gas liquids and sulfur were wasted through the disaster. This meant energy lost to consumers, revenues lost to the company, and royalties and taxes lost to government. According to a report commissioned by ERCB, these and other direct costs totalled about $200 million.http://www.youtube.com/watch?v=Gp9jMIXz1dg
  • Throughout the 26-day period that the well was not on fire, H2S concentrations were generally low. For example, at Lodgepole, the concentrations were less than 1 ppm for 87 percent of the recorded hours, while at Cynthia and Drayton Valley they were less than 1 ppm for about 95 and 96 percent of the time, respectively. In Edmonton, though the odour was detected, the H2S concentrations were actually less than 0.1 ppm for 93 percent of the time." (Lodgepole Blowout Report, 19S5). Health effects were evident as stated in the "ERCB Lodgepole Blowout Report - Causes, Effects, Actions": "Local area residents, and a group of Edmonton respiratory patients, described how the blowout had affected their health. The effects included headache, eye irritation, sore throat, nose bleeds, some breathing problems, nausea and diarrhea. While scientific data was not available to link these health problems to the blowout, the Panel is satisfied that emissions from the well did lead to short-term health effects for a substantial number of people. The evidence also suggests that some people are especially susceptible to H2S emissions.“ Another potential concern was sulphur dioxide. "During the time the well was on fire, and the sulphur was being emitted as sulphur dioxide, the concentrations were substantially less than the evacuation limit." (Lodgepole Blowout Report, 1985). Since Lodgepole, many steps have been taken including establishing exposure limits, improving monitoring techniques and conducting drilling operations in the critical zone in a more cautious manner. The potential for chemical releases does exist from well drilling, pipelines and gas plants and adequate precautions to minimize the risks must be implemented. Crews today have a much higher degree of training.Sulphur dioxide is used in a wide variety of applications, for example, as a preservative for dried fruit, it is used in winemaking, bleaching paper, and chemical reagent applications.
  • Exposure to lower concentrations can result in eye irritation, a sore throat and cough, nausea, shortness of breath, and fluid in the lungs. These symptoms usually go away in a few weeks. Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness.Hydrogen sulfide is considered a broad-spectrum poison, meaning that it can poison several different systems in the body, although the nervous system is most affected. Toxicity of H2S is comparable with that of hydrogen cyanide. It forms a complex bond with iron in the mitochondrial cytochrome enzymes, thereby blocking oxygen from binding and stopping cellular respiration.
  • Thiols, originally ethanethiol, to natural gas, which is naturally odourless. Most gas odorants contain mixtures of mercaptans and sulfides. T-butyl is the prevalent odour component.Mercaptans were added in response to accidents in the early 20th century.
  • Mercaptans are added to create the smell – this allows natural gas to be detected by humans due to the smell. This solution was devised after the New London School incident in 1937.Humans breathing up to 8 ppm of hydrogen sulfide over a two month period experienced nausea, headache, shortness of breath, sleep disturbance, eye and throat irritation.H2S is heavier than air and as such, it sinks to the ground. Vapor Density (Air = 1): 1.176 @ 60F (15.6C)(Calculated)Dissipation into the surrounding environment quickly reduces the ppm content. As such, the most dangerous place is low lying areas directly near the area of the H2S leak.Setbacks have been established so that no wells may be drilled in known H2S areas unless these specific setbacks are in place allowing dissipation of the H2S gas such that it is not harmful to humans or animals.
  • In 1937, the New London School Board cancelled their natural gas contract. Plumbers installed a tap into Parade Gasoline Company's residue gas line. This practice, while not authorized by local oil companies, was widespread in Texas. At that time, there was no market for natural gas and it was thought of as a byproduct, much of it flared off. The raw gas varied in quality from day to day, and from hour to hour.Gas had been leaking from the residue line tap, and had unknowingly built up inside an enclosed crawlspace that ran the entire 253-foot length of the building's facade. Students had been complaining of headaches for some time, but little attention had been paid to it. Since the natural gas did not have H2S content and was “sweet” gas, there was no smell to detect. Approximately 600 students and 40 teachers were in the building at the time; only about 130 escaped without serious injury and estimates of those killed varied between about 296 and 310. This incident caused intense debate and resulted in regulations requiring the addition of odour for detection and numerous other safety measures were instituted as a result of this event.The Leduc Hotel blew up in a similar fashion in 1948, killing several people.
  • One witness said the entire roof of the main facility was lifted several meters off the building and then collapsed back in upon the structure. The resulting tragedy caused many deaths <296-319> The precise number of victims was unknown probably due to the lack of records, transient populations, and no forensic investigative capabilities at the early part of the 20th century.
  • H2S

    1. 1. 6/18/2011 1
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    4. 4.  Used in farming – crop dusting and organic farming applications Nuclear Engineering Epsom salts Laxative Exfoliate And of course.... matches 6/18/2011 4
    5. 5.  Beta lactum antibiotics ◦ Penicillins ◦ Cephalosporins ◦ Monobactums Dermatological treatments ◦ Psoriasis ◦ Eczema ◦ Acne 6/18/2011 5
    6. 6.  Occurs naturally in; ◦ Crude petroleum ◦ Volcanic gases ◦ Hot springs 6/18/2011 6
    7. 7. ◦ Can form from organic materials (plants, human, animal waste decomposition in oxygen-free environments.  It’s called Anaerobic Decomposition and it happens in;  Manure piles  Sewers  Swamps  Composts 6/18/2011 7
    8. 8. Q: If a well has 25% H2S content and is a couple miles away from me... What does that mean to me?A: Many people live near sour gas wells all their lives with no problems at all because it dissipates into the atmosphere and becomes a very small amount of H2S in the atmosphere 6/18/2011 8
    9. 9.  If there is a leak, at that’s rare, the percentage of sour gas in a well quickly dissipates when it incorporates into the atmosphere. Thus, a well that has a 25% sour gas content may only create 1 or 2 ppm in a zone immediately next to the well, and dissipates further from there. 6/18/2011 9
    10. 10. Modeling determines a dispersion zone 6/18/2011 10
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    12. 12.  When a well produces a percentage of H2S it is just that, a percentage. This measurement is not how we sample air quality to determine if there is any danger to people. The air we breath is sampled and reported in ppm – ppm stands for “parts per million” and that’s how we measure H2S in the air... In parts per million. 6/18/2011 12
    13. 13.  You may only be exposed to a fractional ppm if you live near a sour well and if there is a leak You can sit in the hot springs all day at 2 or even 6 ppm, and the same is true for H2S in low concentrations from a well If a sour gas well gets out of control, it is flared to burn off the H2S In Alberta, sour gas well facilities are designed, monitored and highly regulated for the public safety 6/18/2011 13
    14. 14.  Energy Resources Conservation Board AUC regulates sour gas pipelines Strict Engineering Standards are applied to all sour gas well equipment MSDS information is on every well in Alberta. Crews are trained on live wells @ Nisku training site Drillers and Rig Managers are trained and certified in blowout prevention 6/18/2011 14
    15. 15.  6,000 sour gas wells in AB 250 processing plants 18,000 km of pipelines 105 wells within or near Calgary 98% of sulphur removed is converted to elemental sulphur 2007 Data – Gov. Alberta 6/18/2011 15
    16. 16.  Best engineering practices Setbacks to human dwellings and areas Handling and transportation requirements Sensing equipment at sites with redundant backup sensors Flaring guidelines Evacuation requirements (15 ppm) 6/18/2011 16
    17. 17. Lease setbacks areareas large enoughfrom human orlivestock to ensurethere is enoughroom for sour gas todissipate into theatmosphere to a safelevel 6/18/2011 17
    18. 18.  Drill pipe used in sour gas wells must be resistant to corrosion NACE International 6/18/2011 18
    19. 19.  checks for corrosion to maintain pipeline integrity 6/18/2011 19
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    23. 23.  H2S concentration of greater than four parts per million a.k.a. >4ppm in the atmosphere ◦ .0047 ppm // half of humans sense the rotten egg smell ◦ 5 ppm - 15 ppm // alarm ranges ◦ 10 ppm - 20 ppm // borderline concentration for eye irritation ◦ 150 ppm – 250 ppm // Sense of smell disappears ◦ 320 ppm – 530 ppm // Pulmonary edema, potential death ◦ 530 ppm – 1,000 ppm // Rapid breathing to respiratory arrest ◦ 800 ppm // lethal for 50% of humans with 5 minutes exposure ◦ 1,000 ppm // immediate collapse and respiratory arrest 6/18/2011 23
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    25. 25.  Alberta has the toughest H2S regulations that exist in the World with an amazing track record of success. The most famous event in Alberta was the Lodgepole blowout of Nabors Rig 18 while drilling under the Pembina River at a depth of about 3,000 meters. 6/18/2011 25
    26. 26.  1982 – Amoco well blow out 12 miles from Lodgepole (the worst part) ◦ In the atmosphere, no concentrations >10ppm were found within a 20 Km radius ◦ Within the 20km radius, only a few residences were found to have concentrations > 20ppm ◦ Highest concentration measured at Lodgepole was 14.5ppm ◦ Drayton Valley (45km from well) had highest reading of 4.5ppm ◦ Highest reading in Edmonton was 0.5ppm 6/18/2011 26
    27. 27.  Upper Hot Springs – 2ppm Miette Hot Springs – 6ppm Lodgepole –Drayton Valley reached 5ppm Lodgepole –Edmonton reached .5 In Cynthia and Drayton Valley it was less than 1 ppm about 95 and 96 percent of the time and about .1 for Edmonton 6/18/2011 27
    28. 28. Mastrb1asterVideo 1Video 2Video 3Video 4Video 5Landcruiser45Conventional Blow OutdlelementalNabors 18 6/18/2011 28
    29. 29.  During the 26 day period the well was not on fire... ◦ Edmonton – odour detected but concentrations were less than 0.1ppm 93% of the time 6/18/2011 29
    30. 30.  Produced natural gas containing H2S smells like rotten eggs ◦ A very heavy dose can be fatal ◦ It collects in low lying areas because it’s heavier than air ◦ It also deadens the sense of smell ◦ Can burn and irritate eyes ◦ Was used by the British as a chemical agent in WW1 6/18/2011 30
    31. 31. Sweet natural gas has no smell –so we add mercaptans whichcreate that funky smell as thegas is used to heat and cookwithIt’s a safety feature and isdesigned so that humans candetect the odour if there is a leak 6/18/2011 31
    32. 32.  Special chemicals are added in order to make it easy for humans to detect gas leaks Sweet gas without H2S content, is odourless, the mercaptans are added as a safety feature 6/18/2011 32
    33. 33. The school board had plumbers tap into an oilcompanies residue line.Gas leaked into an enclosed crawlspace thatran the entire 253 foot length of the building’sfacade. 6/18/2011 33
    34. 34. Since natural gas is odourless – nobodyhad any idea there was a leak and couldnot possibly predict what would happennext. 6/18/2011 34
    35. 35. 6/18/2011 35