The kind of fire extinguishers for an underwater habitat is an important issue. It should be effective, but must not contaminate the entire atmosphere. A considerable solution might be the Bioversal technology represented by Gröschl Brandschutz GmbH (former Bioversal Umwelttechnik und Handels GmbH) in Austria.
“Our solutions are easily and rapidly applied and almost completely biodegradable, as well as possessing an extremely low eco-toxicity profile considered up to 500 times less harmful than synthetic products. Volatile organic compound (VOC) mitigation and hydrocarbon-encapsulating agents are also incorporated to help reduce emissions from explosive gases by up to 80%.
Bioversal products are user-friendly and compatible with any given material or alloy, in addition to being dermatologically tested via human patch testing in accordance with cosmetic product requirements.”
placeholder image from Wikimedia: BACTERIA ISOLATED IN DAIRY PRODUCT; Rizzelli Stefania; 2015