Private Dominique Sarron Lee did not die from a severe asthma attack but from an acute allergic reaction from inhaling zinc chloride fumes, a coroner's inquiry into his death has found.

The fumes were emitted from the six smoke grenades used during a training exercise in April last year. Private Lee, 21, died after having breathing difficulties and passed out during the training exercise in Lim Chu Kang.

"The cause of the demise is not due to severe asthmatic attack, said state coroner Imran Abdul Hamid, dismissing claims by Private Lee's family that he died from asthma.

Delivering his finding, the state coroner also said that the full-time national serviceman had underplayed his asthma history during his pre-enlistment check up.

Private Lee, a former track athlete from the Singapore Sports School who had a history of asthma, had been declared fit enough to undergo combat training.

"It is the legal requirement to ensure accuracy of information provided, the rationale is common sense...the patient with concern must bring information, relevant and true, for screening to be effective," said Mr Imran.

He added that it is "hard to accept" that doctors at the pre-enlistment screening ought to investigate every enlistee.

Private Lee's uncle Sean Seah said the family rejects the coroner's findings, saying that the military doctor at the medical screening should have asked for the serviceman's medical record rather than just depended on what Private Lee told him.