Two teenagers ran out of a house in flames after gas bottles from which they were allegedly "huffing" exploded.
Kate Nicol said she was at working in Mosgiel when she heard an explosion and rushed outside to see the brick house on fire and "a man on fire screaming", followed by a second blast, just after 2pm yesterday.
"[He was] on the ground still burning and smouldering, and there was another one from the house yelling 'help me, help me, I need some warm water'."
Mrs Nicol said she helped the man - a "tall skinny teenager" - to the footpath, as the Outram Volunteer Fire Brigade and an off-duty Christchurch firefighter arrived at the scene.
The teens, aged 17 and 18, were in critical condition in the intensive care unit at Dunedin Hospital last night.
One has burns to his internal airways and lungs.
Fire Service East Otago assistant area commander Trevor Tilyard said the pair had been "huffing" - getting high by inhaling a propellant - from two 9kg gas bottle before the explosion.
The force of the blast blew off much of the tiled roof, displaced walls and shattered windows and left glass strewn on the other side of the street.
Last night a fire investigator and Dunedin police remained at the cordoned-off scene to determine what triggered the explosion.
Mr Tilyard said that as it was only 5C about the time of the explosion, a heater or hot-water cylinder thermostat could have triggered the blast.
"If they were huffing out of 9kg cylinders, then they would not be able to stop it [the fire] spreading."
It was the first time he could recall an explosion as a result of huffing, and he had a simple message for those wanting to try the practice: "Don't."
"It is just so damn dangerous."
Mr Tilyard said the pair were in for a very long rehabilitation.
Dr Leo Schep of the National Poisons Centre said he was distressed about the incident.
At the level people got a narcotic effect from huffing, "you are getting close to the lower flammability limit, that point where you get sufficient concentration to get an explosion".
- Otago Daily Times