On Oct. 2, 1973 hundreds of residents in central Alberta are forced from their homes after a cloud of hydrogen sulfide spews into the air from an oil well. The threat posed by the poisonous and potentially flammable cloud prompts authorities to seal off a 225-square-kilometre area. This CBC Radio clip looks at the accident and the mass evacuation that it sparked. • Hydrogen sulfide, or "sour gas", is common in sewers, underground mines and oil and gas wells. A by-product of decaying organic matter, the highly-flammable gas is believed to be present in a third of all natural gas wells in Alberta. • Sour gas smells like rotten eggs and can be highly dangerous if inhaled. Exposure to low amounts can cause respiratory problems and headaches, while contact to a high concentration of sour gas can cause a loss of consciousness and death. • Most wells are outfitted with safety mechanisms to prevent the leakage of sour gas. In the case of an accidental leak, workers are trained to set the gas on fire to burn off any sour gas before it gets into the environment. • In October 1973 accident, water got mixed in with the oil and sour gas preventing workers attempts to set it on fire. • The well, which was located 50 miles south of Edmonton, had been inactive for years when it suddenly "blew out" on Oct. 2nd. • According to a front page story in The Globe and Mail "The well, which had been dormant for 10 years, came to life with an eruption about 4:30 p.m. Tuesday, hurling 90 feet of pipe more than 20 feet into the air and spewing out oil, water and sour natural gas." • A spokesperson for the Sun Oil Company which operated the well, told the Canadian Press that crews were doing maintenance work when the well blew. The situation "just got away from them" he said. • The blowing well sprayed particles of sour gas into the air, which within hours gathered into a mile-long cloud of poison gas. The cloud reportedly drifted up to 100 yards a minute and reached about 8,000 feet above ground. • Police immediately sealed off a 140 square mile area around the well as the cloud began to drift. The RCMP alerted residents in nearby villages of New Norway, Gwynne, Ferintosh and Bittern Lake as well as those in the larger Camrose, to be aware of the encroaching cloud. • Around dinner time the RCMP started the evacuation of more than 300 homes in the villages east of the well after the winds shifted in their direction. • Most people left their homes with their pets and a few items of clothing. Phyllis Jensen, whose family lived less than a mile from the well, told the Globe and Mail about her up close experience with the gas cloud. • "It was coming along the ground, a blue fog. It just crept along about waist high." (cont.) • "We were told an automobile travelling in it can ignite it," she added. "Our hired man and his wife said, "Come on, let's get out of here.' We just took our night clothes and moved out." • Ray Chapman, who lived near a few miles north east of the well, told the Globe "I was sitting there watching television and my eyes started to water. Then I began to smell it inside and decided to play it safe [and leave]." • In total more than 700 people fled to emergency shelters in Camrose and Red Deer, where they stayed for at least two days. • About a dozen people were taken to hospital and treated for irritated eyes and throats. Many cases of nausea and chest pains were also reported, but no serious injuries resulted. • The reporter in this clip voices concern over the effect on area cattle, who were left behind in the evacuation. News reports from the following week said none were adversely affected by the sour gas, which dissipated in the upper atmosphere. • An oil company spokesperson in this clip says that the hydrogen sulfide in the atmosphere never reached above two parts per million and is only fatal in concentrations of 1,000 parts per million. • However, Health Canada now says even brief exposures to concentrations greater than 500 parts per million can be deadly. • In August 2005, an explosion at a well in the southern Alberta to

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