Delivering her findings into the deaths of 10 people in Melbourne's 2016 thunderstorm asthma event, a Victorian coroner has asked why people dialling triple-0 were told an ambulance was on its way when, in many cases, it wasn't.

Seven men and three women, aged between 18 and 57, died in the event on November 21, 2016.

Four of the 10 people who died in the November 2016 thunderstorm asthma epidemic: Hope Carnevali (left), Omar Moujalled, Apollo Papadopoulos, and Clarence Leo.

High pollen, strong winds, hot temperatures, air moisture and a cold front combined to trigger severe asthma attacks in people across Melbourne.

From 6pm that day to 6am the next, emergency services received 2332 calls for help, 1400 patients inundated hospitals and the state's ambulance fleet was quickly tied up.