TORONTO -- Health Canada is warning Canadians against purchasing or using “soft-shelled” hyperbaric chambers -- devices marketed online that promise to use oxygen therapy to treat a number of medical conditions, including autism -- due to concerns that such chambers could pose serious health risks and even lead to death.

According to the warning released Friday by the agency, these chambers are “unauthorized medical devices,” and could be dangerous.

Hyperbaric chambers are a legitimate medical treatment -- but so far only in their original, hard-shelled form. A proper hyperbaric chamber is made of steel, and resembles a capsule bed, usually for one person. Patients lie inside these pressurized tubes and breathe 100 per cent oxygen.

“While Health Canada has licensed five hard-shelled hyperbaric chambers for sale in Canada, it has not licensed any soft-shelled devices, meaning they have not been evaluated for safety, quality and effectiveness,” the news release reads.

Health Canada says that soft-shelled, or inflatable versions of chambers could cause disease through cross-contamination of different users, change a patients’ blood sugar levels, or damage ears, eyes, sinuses, lungs and teeth.

A soft-shelled chamber could even catch on fire or explode, the release says, “as a result of static discharge within an elevated oxygen environment.”

According to Health Canada’s page on hyperbaric chambers, the hard-shelled chambers were recognized as an effective treatment for 14 specific conditions by the Undersea and Hyperbaric Medical Society in 2011. Among the conditions or injuries treatable by hyperbaric chambers are carbon monoxide poisoning, anemia, bone infections, radiation burns from cancer therapy and thermal burns.

Some private companies have claimed that these chambers can be used to treat other medical conditions such as cerebral palsy, autism, AIDS and migraines, but Health Canada notes that these claims have not yet been backed up by scientific proof.

It is illegal in Canada to sell or advertise hyperbaric chambers without a license.

Health Canada is asking private companies that sell unauthorized soft-shelled hyperbaric chambers to stop the sales and conduct a recall. The health agency also wants consumers to check which medical devices have been licensed for sale in Canada on their website before they purchase anything.

“Consult your healthcare professional if you use or have used a soft-shelled hyperbaric chamber and you have concerns about your health,” the release advises.