Fire Extinguisher Signs - If used incorrectly, fire extinguishers can pose as much risk as they try to prevent. Untrained, someone using a CO2 extinguisher for example, can asphyxiate in confined spaces. In addition using a water or foam extinguisher on an electric fire can easily result in a pooling effect that can ultimately lead to the firefighter's electrocution. Although it's not technically LAW, By placing the correct Fire Extinguisher Signs next to the fire extinguishers is crucial in giving employees, visitors and the general public clear instructions on using that piece of equipment.