If Junior decides to do this science fair project from the the July 1940 issue of Popular Science, he should probably change the name. The magazine calls this gadget a carbon dioxide “gun,” and he’ll probably get in a lot of trouble if he calls it a gun. If he calls it a “remote fire extinguisher,” he’ll probably get a blue ribbon instead of a visit to the police station.

Like all young men like to do, the two shown here are playing with fire, but making a scientific point in the process. In this William Tell stunt, one young man has a candle on top of his head. The other one puts it out with the Carbon Dioxide Gun–er, I mean remote fire extinguisher. Whatever it’s called, the device is simply a can with a balloon stretched over one end. Inside, a piece of dry ice is placed. When the balloon drum is tapped, an invisible cloud of CO2 is expelled, which causes the flame to be deprived of oxygen.