Now people can have the comfort of a fireplace in their homes without having to worry about air pollution, Superior Fireplace Co of California, US, has designed a natural-gas fireplace which gives natural bright yellow flames of a traditional wood fire, unlike other such units which burn with a blue flame. Superior's Pure Heat unit comes with a catalytic system that helps limit the release of nitrogen dioxide, particulates and other emissions. The unit also includes an oxygen depletion sensor which switches the fireplace off when oxygen levels in the room drop to unsafe levels (Popular Science Vol 250, No 2).