An anti-icing system is provided within a chamber having an exterior wall of which an outer surface may be subject to ice formation. The anti-icing system comprises a nozzle arranged to inject hot gas within the chamber. A gas-mixing device defines a channel for receiving hot gas from the nozzle. The gas-mixing device includes a swirl-inducing feature for causing gas from the chamber to be drawn into the channel with a swirling effect when hot gas from the nozzle is injected into the channel.