Very sudden burning smell in vents that aren't even on.?

Hmmm, yes... I have come across this curious issue before.

What you have, sir. Is a Badger. I kid you not, if you get into your vent, you will find atleast one Badger with a little pot, some brittle wood sticks and a small fire going. They use anything they can get their grubby little paws on, so if you leave an onion out well then its as good as gone because they will take your onion.

Becareful though, a cunning badger is a dangerous badger. You never, ever, know where the sneaky little badger is until.... BAM... he stole your onion. Even then you don't know where the badger is, only that there is a badger and that it did just steal your onion and therefore it was at one stage where your onion once was, and thus you know you have a badger.

DO NOT BE AFRAID! The badger smells fear, and the badger likes fear. The badger must NOT under ANY circumstances know that you are on to him, on he will progressively become worse...

I will, impart on you an ancient tradition for warding off the filthy, disgusting badger. You will require:

1 x Crossbow

1 x Goat

2 x Apples

1 x Onion

1 x Ducktape (this is important, not just any tape - it MUST be ducktape)

1x Household Chair

1. you must lure the Goat into your house using the apples (if your goat does not like apples then you are **** out of luck and you might aswell find a new dwelling).

2. Ducktape the onion to the Goats tail (if the goat does not have a tail or the tail of the goat is not long enough the the ear of the goat will suffice however, this will require 2 onions - 1 for each ear... o.o unless your goat only has 1 ear)

3. Now, ducktape yourself to the household chair so that you blend in with your surroundings (the Badger does not have good site, only good smell... the smell of the goat combined with the smell of the onion will drown out your human smell)

4. Moving as little as possible, sit ducktaped to the chair with the crossbow and wait for the badger.

5. When you See the Badger DO NOT LOAD THE CROSSBOW (this is very important - soooo many rookies load their crossbow, not to mention that I never, ever said buy ammo for the cross bow so if you did that then you good sir just wasted money!)

6. Now... When you see the Badger... THROW THE CROSSBOW AT THE BADGER!

Do not miss the badger, if you do it will become weary of you and you may not get another chance - it will not be so easy to trick the next time.

I wish you goodluck!

P.S. Do not let the Badger go once you have caught it!

examine close to ur furnace interior the basement? might have an electric powered hearth approximately to initiate(shorted wires, or mouse chewed on wires?) i might wager that ur furnace is extremely close to easily below your lounge.