The class of fire determines the type of extinguishing agent used. Commercial kitchens use five types of automatic extinguishing systems:
The building should install sprinklers according to NFPA standards. Sprinklers protecting cooking equipment require separate control valves.
Dry chemical systems
Dry chemicals such as sodium or potassium bicarbonate can extinguish Class B and C fires. Those systems extinguish fires by interrupting the chemical reaction. However, because hot surfaces aren't cooled, reignition can occur.
Wet chemical systems
Wet chemicals are water-based solutions made of potassium carbonate and are used to extinguish Class A and B fires. The solution mixes with grease and forms a soapy mixture that cools and smothers the fire. There's less chance of reignition.
Carbon dioxide (CO2) systems
These systems function by flooding the fire area with carbon dioxide, smothering the fire. Because of increasing concerns of dangerous health effects at high exposure levels, CO2 systems are becoming rare.