Inspirator

An inspirator is a device, similar to a venturi tube and an orifice plate, which mixes a fuel gas with atmospheric air in a precise ratio to regulate burn characteristics. Only the pressure of the fuel gas is used to draw in and mix the air. They are the most simple and common type of mixing device for gas stoves and furnaces. Burners using an inspirator are considered to be naturally aspirated.

In an inspirator there are 2 tubes. The first is a fuel gas pipe with an orifice at the end where the gas comes out. Then in front of this there is another section of tubing with a larger diameter that the gas blows into. Usually (but not always) this second piece of tubing is tapered so that it starts getting narrower downstream from the orifice. Then, at a certain point, it stops getting narrower and either straightens out or starts getting larger again. This gives the fuel and air time to mix. The fuel/air ratio is determined by the ratio of the diameter of the orifice to the diameter of the mixing tube.