Because some rubber is burning.
The first and easiest answer that comes to mind is that there is a problem with the cabin air circulating fan. BUT - - there is not really enuf specific information. Are you sure it is a burning RUBBER smell, or a burning PLASTIC smell, or a burning ELECTRICAL smell? All could point to different problems.
Possibly a problem with one of your belts?
My new car did not smell like burning rubber! When I had a gate smelling like burning rubber, a rubber belt was stuck and instead of turning with a piece of machinery, was caught. I would check the belts in the front of the car and look for one with a worn or burned place on it. It could also be a wire or tube resting on an exhaust manifold or on an exhaust pipe.
Bad heater core.
A flat tire is one possibility
it is most likely the brake calipers sticking, as I recently had this problem on my 2007 dodge grand caravan. They did not do it all the time, but would stick out for a brief period of time after braking, thus causing the burning smell, and then shortly after retract far enough so that there was no longer cantact, and therefore, the burning smell then went away.
when changing the oil sometimes oil can be spilled on the engine block. as your engine heats up it causes this smell. it is completely normal
I advise you to perform a careful examination of your car's brake system.
Most likely the transmission fluid needs to be replaced.
There would have been a strong smell of burning, smoke and dust.
Defrost uses the a/c, if it doesn't smell the same with a/c only on. The smell is coming from the blower motor. Bmw's for example have a problem where the blower blade contacts the plastic housing and causes it to rub/melt.
Rubber tree wood is not safe for burning in a fireplace indoors. Rubber tree would can be burned in an outside fire pit. Sometimes the fumes from rubber tree wood can be toxic.
If you have flickering lights and smell wires burning in your Dodge Caravan, you need to get that checked out by a professional. This actually happened to me once too and my van started on fire, it was horrible.
This would depend on your nose. A bad CMP sensor may cause improper burning of the fuel and can give a smell out the tailpipe. Will the CMP smell? Never. A Ford camshaft syncronizer will squeek and could cause a metallic burning smell.
because that is where you olfactory organs are and something is burning nearby.
It would depend on what is burning.
Clutch slipping? and will probably require replacement
I would like to know, since I also crave the smell of Pine Sol!!!!
SOUNDS LIKE THE BUSHINGS IN THE BLOWER MOTOR Check your heater core...it may be dried out. This can cause a rotten egg smell. can also be valve cover gasket and you just don't smell it when the air isn't on. http://www.autozone.com/servlet/UiBroker?UseCase=S001&UserAction=viewSimpleDiagInfo&Parameters=info
Your car may be on fire.
The starter is burning.
If your talking about cars... If you smell a burning smell, or your red battery light comes on then i would get your alternator checked out!