Mother confronts man she claims sells 'nangs' to her son

A desperate mother has confronted the man who she claims sold dangerous nitrous oxide to her son.

The potentially lethal trend, involving gas canisters called "nangs", is sweeping Queensland's south-east as an alternative to party drugs.

The cannisters are legal to sell and can be used to make whipped cream.

The woman, who cannot be identified, told 9NEWS she fears for her son’s life because of his habit of inhaling the gas for a cheap high.

"He's basically brain dead. He can't remember what happened 10 minutes ago, and this is legal," she said. 

9NEWS cameras were there when the mum came face to face with the man she claims is selling the drug to her son. 

"I told you I was coming after you," she told the man.

"You are using it or selling it to (customers) with the intent of abusing it."

The man denies knowing what the users do with the canisters.

"I'm just selling it with the intent to just sell the product," he claimed. 

One Gold Coast seller claims to deliver up to 6000 canisters to parties across the coast on a single night.

He says he's doing nothing wrong.

"We definitely won't sell it to them if they imply they will be misusing it," he told a VICE documentary.

Inhaling the gas can cause B12 deficiencies that can lead to neural damage. Doctors warn it can cause heart attacks, brain damage and even death.