There are four types of fluids in use:

Type I fluid is the least effective and it is used mostly for de-icing (for washing the aircraft, mixed with hot water). It provides very limited protection for about 5 minutes. It is used only to clean the aircraft when further icing is not expected or as the first step of a two-step procedure.

Type II and IV are used interchangeably for anti-icing, either diluted or not. They are used in the second step of a two-step procedure. They provide a period of anti-icing protection.

Type III is used in the same way as type II and IV, the only difference is that it is designed for slower aircraft.

No anti-icing protection is effective indefinitely. Therefore, there is a time limit during which the anti-icing protection can be considered reliable. Numerous factors that can affect the de-icing/anti-icing performance are:

a) type and rate of precipitation;
b) ambient temperature;
c) relative humidity;
d) wind direction and velocity; including jet blast;
e) aeroplane surface (skin) temperature; and
f) de-icing/anti-icing fluid (type, fluid/water ratio, temperature).