Boss blamed for SA worker's heat collapse

The South Australian branch of the CFMEU has accused an employer of negligence after an apprentice collapsed in the heat at an Adelaide building site.

An employer has been slammed for "utter negligence" after a teenage apprentice collapsed at an Adelaide construction site during a heatwave.

Travis Mellor, 17, remains in a critical condition in hospital after collapsing from heat stroke on the job on Wednesday, the CFMEU says.

"It is utter negligence that his employer did not make a decision to stop work when the temperature had reached 41.5C," SA branch secretary Aaron Cartledge said on Friday.

"Travis is still a child who had no idea of the danger of toiling in these kinds of conditions."

Adelaide is expected to swelter through at least two more days of scorching heat as South Australia gears up for its third consecutive 40C day.

Such a stretch of extreme heat has never been recorded in December before, the Bureau of Meteorology said.

Mr Cartledge said no job was worth a worker's health.

"It's a total abrogation of your responsibility as an employer if you subject people to work in these kinds of conditions," he said.