An aquatic centre in Sydney's south has been evacuated after hydrochloric acid leaked into a spa, landing three people in hospital including a child.
More than 150 people were rushed out of the Hurstville Aquatic Centre on Monday morning when about 70 litres of the acid leaked into a spa area.
It released a chemical vapour cloud in the facility's communal pool area, Fire and Rescue NSW said.
Paramedics treated six people at the scene, with a further three - including a child - taken to St George Hospital in a stable condition.
"When a patient is exposed to any type of chemical there's always an unknown to the extent of their injury," NSW Ambulance Inspector David Stride said.
"Incidents like this can happen in a matter of seconds so it's always important to be aware of your surroundings.
"With the help of FRNSW and bystanders we did a fantastic job in evacuating the entire facility."
FRNSW said the leak is believed to be linked to a malfunction within the pool's automated filtration system.
The acid vapour has been cleared through natural and fan-driven ventilation, although specialists were still monitoring the centre's air quality on Monday afternoon.