The Federal Court on Friday ordered Malcolm Hooper to pay $1 million and his company Oxymed $2 million for promoting the therapy on its website and Facebook page between February and August last year.

The "pseudo-scientific" posts suggested Oxymed's hyperbaric oxygen therapy could be effective treatment for Alzheimer's disease, cerebral palsy, dementia, COVID-19, stroke, HIV/AIDS, cancer, depression and post-traumatic stress disorder.

"The overall impression intended to be imparted to the vulnerable non-scientific reader from the deluge of apparently scientific articles is that HBOT is a credible form of treatment for many diseases and chronic conditions," Justice Helen Rofe said in her written reasons.

"The website and Facebook page are aimed at a vulnerable audience, untutored in science, and many seeking relief from living with chronic conditions, or the carers, friends and relatives of such people."

There was potential for significant harm if patients with cancer or HIV/AIDS deferred or avoided orthodox evidence-based treatment in favour of pursuing the "unproven" hyperbaric oxygen treatment, Justice Rofe said.

She also raised concerns that Mr Hooper's "zealous enthusiasm" for the treatment could see him return to posting material about it on social media.

His lawyer had previously argued that the posts were "educational" and could be likened to a tea shop promoting the health benefits of harmless peppermint tea.

Oxymed's hyperbaric oxygen therapy devices were not registered on the Australian Therapeutic Goods Register.

The TGA warned Mr Hooper about the misleading advertisements in 2018 before laying down an urgent cease and desist notice in March last year.

Hooper and his South Yarra clinic were previously fined more than $700,000 for three workplace safety offences following the death of a vulnerable patient, Craig Dawson, in April 2016.

Mr Dawson - who had multiple sclerosis, epilepsy and used a wheelchair - had a seizure in a unit at Oxymed and died a few days later in hospital.

He had been undergoing twice-weekly, four-hour sessions at Hooper's clinic for 18 months and died following a cardiac arrest.

The Victorian County Court heard that Oxymed had an inadequate risk assessment system in place.

Judge Amanda Fox described it as an "alternative" health facility that people may have turned to when mainstream treatment had failed.

"You do not need medical qualifications to own and operate these sorts of chambers," Judge Fox said.

Experts previously told the court that using hyperbaric oxygen therapy to treat patients with multiple sclerosis was controversial, not supported by scientific data and not approved by Medicare.

WorkSafe Victoria health and safety acting director Andrew Keen said Mr Dawson's death was a "tragic example" of employers not putting safety first.

Hooper and Oxymed were on Friday also ordered to pay legal costs for the Department of Health.

Australian Associated Press