Alumina Trihydrate (Al2O3-3H2O) is the most widely used flame retardant in the world due to its versatility and low cost. Available in different particle sizes, it can be used in a wide range of polymers at processing temperatures below 220°C. ATH is non-toxic, halogen-free, chemically inert, and has low abrasiveness. Additional benefits are arc and track resistance in plastics exposed to electrical arcing, acid resistance, and smoke suppression. At about 220°C, ATH begins to decompose endothermically releasing approximately 35% of its weight as water vapor.

Al2O3-3H2O + HEAT --> Al2O3 + 3 H2O

Alumina Trihydrate acts as heat sink thereby retarding pyrolysis and reducing the burning rate. The water vapor released has an added effect of diluting combustion gases and toxic fumes.