An Auckland local board chair is concerned children are using large nitrous oxide canisters.

The gas is sold legally for whipped cream use, but can also be used illegally as a psychoactive substance. 

The canisters are 3.3 litres, about the same as 300 smaller canisters - known as nangs.

Manurewa Local Board Chair Matt Winiata says after seeing one, he's spotted them littered across streets in his local area. 

"On a 10-minute drive, I came across another 9 of them."

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