Smoke and fire sensors
A report on a cargo hold fire from a number of years ago included a systematic investigation of different types of smoke and fire sensors performances. Not only on fire and smoke, but also on multiple possible causes for spurious warnings. One of the conclusions was that one type/class of sensors was inaccurate. And its replacement by another type strongly recommended.
Pity i dont remember the exact case at the moment. Perhaps someone else does.
As far as i can recall the inaccurate type was sensitive to particles other than smoke and fire related ones. may have been a visual/optical kind of sensor. Decompression was one of the causes of stirring up dust particles in the cargo hold causing these sensors to go off. And the better types being InfraRed IR (heat source).
So in cases like these you would have to know the specific type of sensors before you are able to understand what triggered the sensor, which triggers the warning message, and in what kind of priority, to what kind of warning system. This requires both correct aircraft configuration information and knowledgeable system and data interpretation.
Another issue which became clear from the report is how difficult it can be for pilots and crew to distinguish between smell, smoke, fire. Especially when the source area is not directly visible or accessible.
And combined with other cases ... Is that with a fire a straight course to any airport is the safest solution, followed by immediate evacuation.
These last two lines show how complex such a situation can be for pilots and their decision making.
The very fast reaction in this case suggests .... No more than suggests ... Directly observable smoke or fire. Cause of that smoke or fire unknown.