Standard forced-air heaters make a ton of noise, but Mr. Heater’s battery-powered model cuts sound pollution by half. Its brushless DC fan eliminates the need for high fuel-nozzle pressure. Lower pressure allows combustion noise to disperse.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.