Faint burnt smell coming from Mac Air

I've been been smelling a faint burning smell coming from my late 2010 13" Mac Air A1369. I can't exactly pinpoint the source but on the bottom shell I'm feeling some heat coming from the 'general area' of the right side (looking from the top) of the SSD storage drive, roughly 0.5" down from top edge and 6-7" from the left. The area feels much warmer than the area around the mag safe connection which is normally warm. The smell kind of comes and goes. More details:

-I have not yet opened the laptop

-smell is unchanged whether the Mac Air plugged in on mains or running on battery

-smell started yesterday

-smell seems to still occur when laptop turned off but charging

-smell does not occure turned and disconnected from battery

-I have reset the Mac Air's PRAM and SMC

-my battery is not user-removable

-I have been the only owner, purchasing it from Apple in 2010.

-the fan does not come on both otherwise it has been running on other occasions.

-the Mac Air has a 2.13 GHz process, 4 GB of memory, and a 128 GB drive, with about 50 GB available.

-I cannot correlate this issue to anything else, HW or SW event-wise that has occurred recently

-all parts original, laptop has enever been taken apart

-laptop is always used while it sits on an open air laptop support stand 3" off tabletop

Can anyone help me figure out what the problem is and what to do?

Thanks in advance

Mike