O fermento em pó de dupla ação normal faz CO2 (dando assim um efeito de aumento) de duas maneiras: quando fica molhado e quando é aquecido.
O bicarbonato de sódio só produz CO2 quando fica molhado.
The acid in a baking powder can be either fast-acting or slow-acting.[6] A fast-acting acid reacts in a wet mixture with baking soda at room temperature, and a slow-acting acid will not react until heated in an oven. Baking powders that contain both fast- and slow-acting acids are double acting; those that contain only one acid are single acting. By providing a second rise in the oven, double-acting baking powders increase the reliability of baked goods by rendering the time elapsed between mixing and baking less critical, and this is the type most widely available to consumers today.