The Slater Street Explosion

25 October 1958

Saturday, 25 October 1958 started as a typical, mid-autumn, weekend morning in the nation’s capital. It was overcast, and there was a cool crispness to the early-morning air. Downtown streets, which on a week day would have been thronging with civil servants on their way to work, were largely deserted. The stores that lined Sparks Street had yet to open. Ottawa’s cinemas, whose Saturday morning cartoons attracted hundreds of children, were still shuttered. Shortly after 8am, when most Ottawa citizens were still at home having breakfast, or reading the morning newspapers, the city’s usual calm was shattered. A tremendous explosion rocked the downtown core, obliterating buildings on Slater Street, blowing out store fronts, and shattering windows from Sparks Street to Somerset Street. Downtown residents who were indulging in a Saturday morning lie-in were rudely thrown from their beds. Some thought that a plane had crashed, while other believed it was an earthquake. Reflecting Cold War jitters, some feared that Ottawa had been the target of a nuclear attack.

Slater Street explosion
View of Slater Street, October 1958. The Addressograph-Multigraph building has been completely destroyed. In the mid-ground is the ruin of the Odeon Theatre, author unknown

It was quickly determined that the centre of the blast was the Addressograph-Multigraph building located at 248 Slater Street. At 8.17am, William J. Anderson, the building’s janitor, entered the basement of the building to retrieve some cleaning materials. Smelling a bad odour, he switched on a light to get a better look. The light ignited natural gas that had seeped into the basement through a disused, uncapped, gas main.  The gas explosion in turn blew up the building’s oil tank and boiler. Later in hospital, he reported to police that there had been a “rumble and a terrific explosion.” Anderson, who received third-degree burns over most of his body, later died of his injuries.

The massive explosion, estimated to have been the equivalent of a 1,000-2,000 ton bomb, totally destroyed the Addressograph building. Neighbouring Meyers Motors offices and showroom at 260 Slater were also demolished, as was the Odeon Theatre at 142 Bank Street which abutted the Addressograph building at the rear. The back of the cinema was reduced to a mess of twisted girders and fallen masonry. The Jackson Building, where thousands of civil servants worked, situated at the corner of Slater and Bank Streets across from the Addressograph building, was also severely damaged. Virtually all its windows were blown out; debris, sent high in the sky by the force of the blast, littered its roof. Major-General H.A. Young, the deputy minister of public works, said that the building had been reduced to “a shell.” So twisted were its elevator shafts that all twelve elevators were out of commission; filing cabinets and furniture were later retrieved using external hoists. Remarkably, however, the sturdy, nine-story office building, the tallest in Ottawa, remained structural sound, and was later repaired. Touring the site of the explosion by helicopter, a Citizen reporter described the scene as just like “bombed-out, wartime London.”

The first alarm was sounded by Guy Lebel, an off-duty fireman attached to the No. 4 Fire Station. He had been standing on Slater Street when the explosion occurred. Hearing a loud noise and breaking glass, he turned to see a car flung high into the sky. Two hundred firemen and sixty Ottawa policemen and RCMP officers responded to the alarm. The injured were located and quickly cared for, the area promptly secured. Fortunately, as the explosion occurred early on a Saturday morning, there were relatively few casualties. Major-General G.S. Hatton, the deputy coordinator of civil defence, estimated that had the explosion occurred on a week day, 600 casualties might have been expected, with many lives lost. Even so, it was bad enough. In addition to poor William Anderson, the janitor at the Addressograph building who lost his life, forty people were injured, some seriously. Most were struck by flying glass. Bill Smith of Gloucester Street was struck by glass as he was walking down Laurier Street, several blocks away from the site of the explosion. He needed thirty-two stiches to his arms and legs to close his wounds. Glen Dinsmore and Joe Moreau, who worked at Meyers Motors, were also seriously injured by glass and falling masonry. Miraculously, Herb Rawson, the car dealership’s parts manager, escaped unscathed. He had just stepped out of his office to go to the stock room when the blast occurred. The roof of his just-vacated office caved in, burying his desk under two tons of rubble.

In addition to the casualties, twenty-five businesses were closed indefinitely due to the explosion. The Odeon Theatre never reopened; its last show was the sexy, restricted movie …And God Created Woman, starring the up-and-coming French starlet, Brigitte Bardot. Other stores forced to close included the Levey Sign Company, Hobbyland, the Stage Door Restaurant, and the Sherwin-Williams paint shop. More than one hundred residents in the Sula, Imperial, and Cairo apartment buildings located on Slater Street had to be evacuated. Two schools, the Kent Street Public School and the Eastern Ontario School of Technology, were temporarily closed, while the 2,000 government employees working at the Jackson Building were forced to relocate while the building was repaired; many went to the #1 “Temporary” building on Wellington Street.

Officials from the gas company, the federal, provincial, and municipal governments, and the Fire Marshal’s Office immediately descended onto the blast site seeking answers. Prime Minister Diefenbaker, who came to view the scene of the explosion, called it “the most appalling thing” that he had ever seen. Prince Philip, who happened to arrive in Ottawa a few days after the explosion, also inspected the damage. He asked Ottawa’s Mayor Nelms for a personal report on the causes of the blast.

Prince Philip and the Slater Street Explosion
H.R.H. Prince Philip at the site of an explosion at the Addressograph-Multigraph of Canada Company Ltd, 248 Slater Street, 30 October 1958.Andrews-Newton Photographers Fonds/ City of Ottawa Archives/MG393-AN-060432

Mayor Nelms established a five-man commission headed by Major-General H.H. Worthington to establish the causes of the disaster, and to make recommendation on ways to avoid similar incidences in the future. But the commission had barely begun its investigation when it ran into legal problems, and was disbanded. Apparently, under provincial law, it did not have the authority to call witnesses. To replace the commission, the provincial attorney-general ordered a inquest into the death of William Anderson, instructing the coroner, Dr Roger Rouleau, to make a “broad inquiry” into all facets of the fatal disaster.

More than seventy witnesses testified in front of the five-member coroner’s jury, whose foreman was Dr E.R. Birchard, former vice-president of the National Research Council, and a member of the disbanded civic inquiry commission. Expert testimony concluded that the explosion had been caused by a highly explosive mixture of gas and air that had been touched off when Anderson turned on the basement electric lights in the Addressograph building. The source of the natural gas was a 1 ¼ inch supposedly decommissioned gas service pipe that had years earlier been used to supply manufactured (coal) gas to the building. The explosion started in the south-west corner of the basement adjacent to Myers Motors, with the “flame front” moving easterly through the service room, the oil tank room, and finally, the boiler room, which became the epicentre of the blast.

Witnesses reported that when natural gas was introduced to Ottawa in January 1958, the Ottawa Gas Company, a subsidiary of Consumers Gas, had re-used the gas mains that had previously delivered manufactured gas to Ottawa residents. The disused and uncapped pipe in the basement of the Addressograph building had been forgotten; employees in the building believed it to be a rusty, unused, water pipe. Although the pipe had been blocked over time by sludge and debris, the natural gas introduced into the mains gradually eroded the “stoppage,” which finally gave way during the night before the explosion, allowing gas to flow unimpeded into the Addressograph building’s basement. Ironically, just two days before the explosion, Ottawa Gas has assured Ottawa’s Board of Control that “no explosion hazards” existed “in relation to the Ottawa Gas Company’s mains in the city streets.”

The coroner’s jury came up with a number of recommendations that were later implemented to help ensure against a future disaster. These included the establishment of a board with the authority to inspect gas distribution systems, the maintenance of plans and records of underground gas pipelines and mains in municipal offices, and the requirement of a permit from a competent authority before the installation of gas distribution systems. Ottawa Gas was also required to cap all disused gas service lines, with disconnections done on the outside of buildings. Over the following year, Ottawa Gas complied, disconnecting more than 2,000 disused gas lines, and installing 1,000 shut-off valves.

Site of Slater Street Explosion
Site of Slater Street Explosion, 2015

Not surprisingly, the explosion initiated a flood of law suits. Most importantly, the owners of the Odeon Theatre sued Consumers Gas, the Addressograph-Multigraph Company, the owners of the A-M building, and the City of Ottawa for $1 million. The suit was later reduced to $500,000. The Government of Canada also sued the gas company to cover the cost of repairing the heavily damaged Jackson Building. By the end of 1960, Consumers Gas had reached out-of-court settlements with roughly 400 plaintiffs, mostly area residents and shop owners. The company paid out $1.3 million, of which $375,000 went to the owners of the Odeon, and $500,000 to the federal government. Thankfully for city managers and taxpayers, the company covered all costs.

Today, 248 Slater Street, the site of the destroyed Addressograph-Multigraph building, is a parking lot.


City of Ottawa, The Slater Street Explosion,

The Ottawa Citizen, 1958. “No Explosion Hazards In Ottawa Gas Mains,” 23 October.

———————–, 1958. “Janitor May Hold Key To Explosion,” 27 October.

———————–, 1958. “The Bank Street Explosion,” 27 October.

———————–, 1958, “On Week Day: 600 Casualties,” 27 October.

———————–, 1958. “Affects Thousands,” 27 October.

———————–, 1958. “From Air, ‘Just Like Bombed-Out War-Time London,” 27 October.

———————–, 1958. “Man Tells Of Terrifying Brush With Death,” 27 October.

————————, 1958. “First Alarm Sounded By Off-Duty Fireman,” 27 October.

————————, 1958. “Blast Inquiry Set Up,” 28 October.

————————, 1958. “Prince Philip Inspects Scene of Explosion,” 31 October.

————————, 1958. “Tale Of Rusty Pipe In Blasted Building,” 12 November.

———————-, 1958. “Inquiry Into The Explosion,” 15 November.

———————–, 1958. “Slater Pipe Under Scrutiny,” 15 November.

———————–, 1958. “Move To Avert New Explosions; Mayor Issues Orders,” 18 November.

———————–, 1958. “Mains Spill Death,” 18 November.

———————–, 1958. “Board Directs Gas Mains; $1 million Suit by Odeon,” 18 November.

———————–, 1959. “Slater Street Blast Rocked Us Year Ago,” 24 October.

———————–, 1960. “Actions,” 22 December.

Urbsite, 2012. Bank and Slater Streets, 3 September,


View of Slater Street, October 1958. The Addressograph-Multigraph building has been completely destroyed. In the mid-ground is the ruin of the Odeon Theatre, author unknown, Urbsite,

H.R.H. Prince Philip at the site of an explosion at the Addressograph-Multigraph of Canada Company Ltd, 248 Slater Street, 30 October 1958. Andrews-Newton Photographers Fonds/ City of Ottawa Archives / MG393-AN-060432-001, City of Ottawa Archives.

248 Slater Street, site of the Addressograph-Multigraph building, today. Google Street View.

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