Sticky riot foam is a non-lethal riot control concept that has been proposed for some time but is yet to see widespread use, due largely to the risk of suffocation if it covers the mouth and nose. In addition, in trials of sticky foam as a riot control weapon it took several hours to completely decontaminate a subject using baby oil, as it adheres immediately to skin and clothing. Nonetheless, its use is still in discussion.
Sticky foam starts as a non-reactive liquid that is stored at high pressure. When it is released, such as being fired out of a backpack-mounted dispenser, the atmospheric pressure causes it to expand to over 30 times its storage capacity. It is composed of rubbers, resins, fire retardants, oils and foam-stabilising chemicals and is about ten times stronger than syrup. The foam’s tensile strength allows it to stick to objects and significantly slow their movement, and it has been touted as being used to either slow a person or a vehicle.
Above is a view of the first back-pack developed at the Sandia National Laboratories for dispensing ‘sticky riot foam’. The weapon can fire up to 10 metres and immobilises the target long enough for handcuffs to be applied. It was part of the ‘Less-than-Lethal’ programme of the US National Institute of Justice, and was originally intended to replace firearms as a ‘first resort’ weapon.