The 24-year-old student was hit by flying glass and breathed in poisonous chemicals which are thought to have caused a lung embolism, police in Karlsruhe said on Thursday.
The organic chemistry students were clearing up after an afternoon's lab work in the Karlsruhe Institute for Technology (KIT) on Wednesday when a mix of nitric acid and sulphuric acid came into contact with an organic chemical.
The glass beaker containing the left-over acids exploded, scattering acid, poisonous fumes and pieces of glass across the laboratory. Police estimated that around €10,000-worth of damage was caused.
All those in the lab inhaled the gases, which led to some breathing difficulties, police said in a statement. The 24-year-old student was seriously hurt and was taken to accident and emergency at the local hospital.
The others were taken to various hospitals nearby for examination, as was a firefighter who suffered a chemical eye injury.
The building was evacuated while firefighters carried out tests for chemicals, but found no danger. Karlsruhe police were on Thursday collecting evidence to establish what had happened, but there was no immediate suspicion of foul play, a spokeswoman told The Local.