Fire fighting foam is a type of foam that is used to suppress fire. It cools the fire by coating the fuel. Coating the fuel prevents it from getting in contact with oxygen and this results in the suppression of the combustion. A Russian chemist and engineer, Aleksandra Loran, invented fire fighting foam. The chemicals used should produce foam that has less than 1% concentration. Fire fighting retardant foams are made from solvents that include hexylene and glycol, foam stabilizers and corrosion inhibitors. There are different types of fire fighting foams as discussed below. Currently AFFF is the most widely used out of all of the ones on the market.
Class A Foam does not expand a lot and have an expansion rate that is less than 20 times. Foams that have expansion ratios of between twenty and two hundred are medium expansion. Low expansion foams are less viscous, mobile and can be used to cover large areas within short durations of time. Fire fighting foams that have more than 200 expansion ratio are classified as high expansion forms. They are most suitable for enclosed spaces like hangars where there is need to quick fill in case of fire.
Alcohol resistant foams have polymers that form a protective layer between the foam and the burning surface. This prevents foam breakdown in the burning fuel by alcohol. Most alcohol resistant foams are used for fighting fires of fuels that contain oxygenates or fires that are caused by liquids that contain polar solvents.
Protein fire fighting foams contain proteins as the agent. Protein foams, unlike synthetic foams, are bio-degradable. They spread and flow slower but provide a foam cover that is more durable and heat resistant.
Every type of foam acts effectively when used with different fires. For enclosed spaces such as hangars or basements, high expansion foams are used because the space must be quickly filled before the fire spreads. For burning spills such as spills of jet fuel, low expansion foams are used.