Potassium bicarbonate (also known as potassium hydrogen carbonate or potassium acid carbonate), is a colorless, odorless, slightly basic, salty substance. According to the US Food and Drug Administration (FDA), potassium bicarbonate is "generally recognized as safe"
The compound is used as a source of carbon dioxide for leavening in baking, extinguishing fire in dry chemical fire extinguishers, acting as a reagent, and a strong buffering agent in medications.
It is used as a base in foods to regulate pH. It is a common ingredient in club soda, where it is used to soften the effect of effervescence.
Potassium bicarbonate is used as a fire suppression agent ("BC dry chemical") in some dry chemical fire extinguishers, as the principal component of the Purple-K dry chemical, and in some applications of condensed aerosol fire suppression. It is the only dry chemical fire suppression agent recognized by the National Fire Protection Association for firefighting at airport crash rescue sites. It is about twice as effective in fire suppression as sodium bicarbonate. 
Potassium bicarbonate is an effective fungicide against powdery mildew, allowed for use in organic farming.