City staff are probing the use of other cooling agents at Toronto arenas after three people died from exposure to ammonia at an ice rink in B.C. last week.

The gas leak at an arena in the tight-knit mountain community of Fernie, B.C. — located some 300-kilometres southwest of Calgary — has sparked debate about the use of ammonia refrigeration systems in similar facilities throughout Toronto.

While the "vast majority" of the city's ice surfaces are cooled by ammonia, Matthew Cutler, a spokesperson for Toronto Parks, Forestry and Recreation, says the likelihood a similar leak would occur here is slim.

"It's extremely uncommon," he said, noting the incident in B.C. marked the first fatal one at a rink in Canada.

3 workers died at B.C. arena

Ammonia was to blame for the deaths of three men last week, including two city employees and a refrigeration worker, at the Fernie Memorial Arena.

Fernie Fire Chief Ted Ruiter told CBC News two victims were found dead inside the arena when first responders arrived. Someone was performing CPR on the third victim, who died at the scene, he said.

They were identified as Wayne Hornquist, Jason Podloski and Lloyd Smith.

It's not yet clear why the three rink workers weren't tipped off by the pungent smell ammonia gives off when it leaks.

Ammonia most popular in Ontario

The chemical responsible for the deaths is anhydrous ammonia, a noxious gas when released into the air that can cause fluid to accumulate in the lungs if inhaled, according to the Canadian Centre for Occupational Health and Safety.

Ammonia is commonly used in mechanical refrigeration systems, including those found in ice rinks. The chemical, which runs in pipes below the surface, has kept ice cold in arenas across the country since 1915.

It's also used in fertilizer and to make plastics, fibres and other chemicals.

Ammonia refrigeration systems are used in 80 per cent of Ontario rinks, expert says. (Adrian Cheung/CBC)

Ammonia is most popular in Ontario where it features in roughly 80 per cent of ice rinks in the province, said Daniel Giguere, refrigeration and heat pump expert with the federal Ministry of Natural Resources.

And banning the chemical, says Terry Piche, technical director for Ontario Recreation Facilities Association, is probably "out of reach" for many recreation providers due to high re-furbishing costs.

Other cooling agents

As an alternative, Cutler says Toronto arenas are looking into carbon dioxide and halocarbons, although he maintains ammonia is the safest option for cooling rinks.

"Over time we have actually been phasing out ammonia within those systems to minimize the amount of ammonia that is used," he said.

"Previously, ammonia was used as a refrigerant, but also it was pumped under the ice to freeze the ground. We've actually moved to more environmental solutions under the ice and ammonia is only used now in the actual refrigeration process."

The City of Toronto says modern ammonia refrigeration systems do present risks but are still safer than other alternatives. (CBC)

Carbon dioxide not only keeps the ice cold by reducing the level of greenhouse gases emitted, but also meets the city's safety protocols, Cutler said.

Halocarbons, such as freon, present safety concerns of their own. In recent years they have fallen out of favour, in part, because they are potent greenhouse gases.

Ammonia levels checked daily

While the city explores these options, Cutler says skaters have nothing to worry about because ammonia levels are checked daily.

"There's also sensors and either visual or audible alarms placed in the compressor room in each of the refrigeration locations so if there is an active leak an alarm will go off," he explained.

"All of those are connected then through to our refrigeration teams."

Prevention tactics are also employed as a "normal course of business," he added, noting operators conduct daily on-site visits where ammonia levels are checked.

Skaters don't have access to that equipment, which is stored in an "entirely different room," said Shari Lichterman, director of recreation for the City of Mississauga.

"The room is locked, it's separate and accessible only by trained staff," she said.