CALGARY – A new report detailing a mass carbon monoxide exposure that sent dozens of young hockey players to hospital is renewing calls for mandatory detectors in Canadian arenas, where federal guidance recommends the devices, but does not require them. The incident involving four youth hockey teams made up of 10- and 11-year-olds unfolded in December 2024 during a weekend tournament at an arena in Rockyford, Alta., about 90 kilometres northeast of Calgary. Three parents involved that day — Jessica Marshall, Dan Moir and Laurie Lee — are among the authors of the report detailing the exposure in the Canadian Medical Association Journal. Players began reporting headaches, fatigue, dizziness, nausea and vomiting after spending much of the day inside the arena because of cold weather and back-to-back games. At first, many parents thought a virus was spreading. Marshall’s son, a goalie, had played his first game without issue. During the second, while sitting on the bench, he suddenly became violently ill and ran into the change room. “He’s got his head in a bucket and he is puking and screaming, trying to get his hockey gear off of him,” Marshall said. ‘Something’s going on’ Moir, an off-duty firefighter whose son was also playing, initially thought the same thing. “My son actually came off. Had a little bit of headache, wasn’t feeling good,” Moir said. Then another player arrived with a headache, nausea and dizziness. A third soon followed. “I was like, all right, something’s going on.” Moir began to wonder whether carbon monoxide (CO) could be responsible. While driving home, he called the local fire department, which sent a crew to the arena. Firefighters detected CO levels ranging from 90 to 150 parts per million and evacuated the building. “There’s two different alarms for most detectors, like a low alarm and then a high alarm,” he said. “The detector went into high alarm right away.” Moir was not initially informed of the test results. He contacted the arena manager himself and learned elevated CO levels had been detected and the arena had been evacuated. According to the CMAJ report, he was given no guidance about what players and family members who had already left should do. Moir then called Lee, another player’s mother and a pediatric nurse practitioner who was not at the arena. Her son, who was also on the team, had experienced mild symptoms. Lee advised anyone who remained symptomatic to go to the emergency department for assessment. “No way did I think I’d be calling the Children’s (Hospital) to say, ‘I’ve just sent 40-plus children in for assessment for a toxic carbon monoxide exposure,’” Lee said. ‘A terrifying wake-up call’ Marshall’s family had already left the arena believing her son might simply be sick. They were preparing to put him to bed when they learned he may have been exposed to carbon monoxide. “If we had put him to bed, we don’t know what would have happened at that situation. And it’s a terrifying wake-up call as a parent.” The CMAJ report states that at the Alberta Children’s Hospital, 23 children and two adults — by then more than three hours after the exposure — had CO levels requiring treatment and monitoring. No children were admitted to hospital, while both adults were transferred to an adult hospital. The patients arrived during one of the hospital’s busiest times of year, amid the December surge in respiratory illnesses. The emergency department was already over capacity when staff learned dozens of children could be arriving with carbon monoxide exposure. Paramedics screened exposed children and caregivers at the emergency department entrance using a non-invasive device to measure CO levels. Only those with readings above three per cent were brought into the department, where they were placed on oxygen and underwent blood testing to confirm their levels. Lee said carbon monoxide interferes with the body’s ability to deliver oxygen to vital organs, which leads to symptoms such as headache, nausea, dizziness and vomiting. “My priority was making sure that they all were seen by a medical professional and got whatever treatment needed,” Lee said, adding the treatment is high-concentration oxygen. Marshall remembers the chaos as families descended on the children’s hospital. “We were 40-plus kids coming in. All the parents could not come in at the same time,” she said. Her son’s CO level was measured at nine per cent, among the highest on his team. He was given continuous oxygen and underwent repeated blood tests and electrocardiograms until his level fell to a safe range. The source of the carbon monoxide was traced to a blocked heater exhaust in the hockey team’s dressing room. The arena did not have CO detectors. In a statement to CTV News, the Village of Rockyford said permanent carbon monoxide monitors were installed during the off-season and additional safety measures were introduced, including portable CO monitors, upgrades to the heater exhaust system and air exchange fans, and new policies and procedures. The village said it worked with the Rockyford Agricultural Society and Occupational Health and Safety on the changes, noting there were no safety codes requirements for CO monitors at the time of the incident. Alarm guidance is voluntary Health Canada recommends arenas install and maintain carbon monoxide alarms, but its guidance is voluntary. Vittoria Vecchiarelli, an Ontario-based certified public-health inspector and author of a related CMAJ commentary, said a properly configured alarm could have provided an earlier warning. “A carbon monoxide sensor with an alarm set at the right level would have alerted staff and players and parents,” she said, “and then action could have been taken sooner.” The Rockyford incident was not an isolated one. Vecchiarelli said at least 11 CO and one nitrogen dioxide (NO2) poisoning events were documented at Canadian ice arenas between 2016 and 2026, adding that the documented incidents may not capture the full extent of exposure in Canadian arenas. “There’s no central catalogue where we can find a list of all the events, and we don’t know how often individuals are exposed to elevated levels that don’t prompt medical attention or intervention and/or emergency evacuation,” she said. For Vecchiarelli, the incidents underscore the need to move beyond voluntary recommendations. “We need to set enforceable limits for carbon monoxide and nitrogen dioxide, and require the installation of carbon monoxide sensors with alarms,” she said. For families who spend much of the winter inside hockey arenas, the incident has also raised concerns about what repeated exposure could mean. “We are 10 years into being a hockey family,” Marshall said. “We live at small rinks on the weekends. Never in my wildest dreams did I ever see this happening.” Lee said while the most severe consequences of acute CO poisoning are well-known, there are also concerns about delayed symptoms and neurological problems associated with chronic exposure. “Though we worry most about the sudden death of kids that are sleeping in an environment with high carbon monoxide, there are worries about delayed presentation and seizures and headache and confusion and memory and learning difficulties in kids that have chronic, ongoing exposures,” she said. For children who spend significant amounts of time in arenas, including her own son, Lee said the possibility of repeated exposure is concerning. CO is an odourless, colourless gas produced by incomplete fuel combustion. The blocked heater exhaust was identified as the source in Rockyford, but Vecchiarelli said there are other potential sources inside arenas, including fuel-powered ice resurfacing equipment and heaters, which can emit CO and (NO2). “There are guidelines published by Health Canada and various provinces to improve air quality in ice arenas, which include the recommendation to install air monitoring equipment,” she said. “However, they’re not enforceable.” She pointed to Minnesota, where indoor air quality regulations include routine arena inspections, education and enforcement. “They’ve had great success reducing carbon monoxide poisoning events and compliance among arena operators,” she said. She added that arenas should also regularly maintain fuel-burning equipment, ensure sufficient ventilation and be encouraged to switch to electric ice resurfacing equipment to eliminate CO and (NO2) emissions from that source. For Marshall’s family, the experience has already changed how they approach every rink they enter. Her son now travels with a CO monitor clipped to his hockey bag. His coach has also purchased one for the team. “It sits on my son’s hockey bag and it gives him peace of mind,” Marshall said. Lee said the authors hope the report will have an impact beyond the Rockyford incident. “We really wanted to publish this in a highly regarded medical journal, so that the story of what happened to these kids could be accessed by health-care professionals across the country,” she said, “and people that want to do research in the area of carbon monoxide exposure and prevention.” For Marshall, the experience has left her wondering why monitors aren’t already required. “You hear a couple different incidences that have happened and you wonder why they haven’t changed the regulations,” she said. “It’s not hard. It’s an easy fix to do. They need to do something to fix it.” CTV News reached out to Health Canada for comment but did not receive a response by deadline.
