Which of the following is NOT an unusual location for a fire, according to training bulletins about arson?

The choice that identifies an area that is NOT typically regarded as an unusual location for a fire is over the stovetop. This area is a common and expected place for fires to occur, particularly in residential settings where cooking is done. Fires in kitchens, often ignited by cooking activities, are well-documented and can be attributed to everyday occurrences such as grease fires or stovetop mishaps.

In contrast, the other options represent locations that are more atypical or concealed, which would raise suspicion in the context of arson. Areas like under a stairwell, inside a closet, and in a dumpster are less likely to be areas where fires start due to routine activities and may indicate deliberate attempts to commit arson or other criminal acts. This understanding helps identify patterns in fire incidents that may warrant further investigation when assessing potential arson cases.