What common feature is found in all portable fire extinguishers?

All portable fire extinguishers are equipped with a pull pin mechanism. This feature is a critical safety element designed to prevent accidental discharge. The pull pin must be removed before the extinguisher can be activated, ensuring that the user has a chance to aim the extinguisher properly and is ready to engage it safely.

The pull pin mechanism is standardized across different types and classes of extinguishers, making it a commonality among them. While it is true that some extinguishers may contain specific agents like water, foam, or powder, not all extinguishers employ the same extinguishing agents, so that cannot be considered a universal feature. The requirement for a pressure gauge is also not applicable to all types of extinguishers, as some extinguishing agents do not utilize pressurized systems. Therefore, the pull pin mechanism stands out as the common feature found in every portable fire extinguisher, allowing for consistent and safe operation.