Unlikely to burn the house down, but computers oughta be cheap for a guy with fancy light fixtures and magic finger beds.
Desktop or laptop?
If its a laptop, might only have 1 fan on the cpu and one for the system.
If a desktop, might have a power supply fan, a video card gpu fan, a cpu fan, and possibly a second separate case fan. Some of the older Dell designs also used one on the PS and one to both cool the cpu and evacuate the case.
You may be able to go into the BIOS setup and one of the setup areas may show the different fans and what their rpm's are.
Or you could try out something like this that can tell you what the temps and fan speeds are...if this one doesnt work, look for some others. Some work with some motherboards and sensors, some with others...
Download SpeedFan - Access temperature sensor in your computer