Extinguishers always have some type of pressure gauge or test button on them, along with a gross weight to indicate a proper full charge. As long as you look them over every once in a while, the odds are quite high that they will work. But most folks don't realize a "liter" sized extinguisher is about enough to put out a trash basket or a skillet, and a grease fire will often just spread if you hit it with a regular extinguisher. Either way once it spreads, you need more extinguisher, FAST. And they're all not the same, not all equally effective on everything. Then there are the cushions
, which are almost always urethane foam, which produces nasty toxins very quickly and also makes darn good fire kindling.
Will they work? Almost always. Will that be good enough? Maybe.