On determining the mass - loss rates of red giants and red supergiants based on infrared data

I review existing methods for determining mass-loss rates of red giants and red supergiants based on infrared data. The simplest method is based on models for the absorption and emission by dust which forms in the dense outflows from these cool stars. I discuss the parameters and assumptions upon which the method relies, review relationships between the mass-loss rate and infrared colours or far-infrared flux density, and propose a new formula for the mass-loss rate as a function of the visual extinction. I also briefly discuss the use of atomic and molecular transitions at infrared wavelengths.