Odor in 2008 Prius

isn't it the vent tubes for the hybrid battery?

 

3 things cause odor in a G2.

1---Poorly maintained AC evap box under the dash. Smell the ac vents if the smell is there its easy to fix buy Kool It on amazon.com and inject that up the ac condensate drip tube under the car. Kool It is cheap if dealer does that is about $150. If thats never been done the condenser in front of the rad is probably bug caked and killing your ac efficiency. First time use 2 cans. The drip tube may be clogged and its dumping nasty condensate on the front passenger carpet. Again not maintained.

2---Inside the hybrid battery metal box there's 2 long thin black rubber tubes. Many reports of the stench of those as they get old and break down. they smell really bad.. Lots of posts about that. Some cars get it some don't. I am lucky so far. Smell the hybrid battery cooling vent its in the backseat between the passenger seat and the door about shoulder high its a small vent. Smell that vent and see if the stink is in there.if so battery box needs to come out and those rubber tubes replaced.

3---The interior of your car got wet and the carpet is soaked usually in the backseat. Very common as G2's leak.

You may just bought it. It may be a salvage car. Lots and lots of those from flooded states. And carpet got soaked. Yours may have a bad leak in the trunk and the rear hatch is filled with stagnant water. Lots of G2's leak water mine does. Comes from a crack in the body seam where the roof and the quarter panel meet. Easy to see the crack its in the top corner valley of the rear hatch. Usually pass side.

Take the hatch cover out remove the spare tire and look for water. Get a flashlight and look in the bottom of the 12 volt battery well it probably has standing water. There's a rubber plug in that well you can remove and there's a rubber plug below the spare tire you can remove.

 

Trying to track down the source of the odor is the first step, and not necessarily easy.
Without knowing where the odor is coming from, it's hard to suggest what you need to do.

Is it coming from the air circulation system?
Is it coming from any particular area?

What you would do for a smell coming from the AC or circulation system is quite a bit different from what you would do if you find a leak, or some area of your vehicle that is molding.

First step is narrowing this down.

 

If you haven't already checked the cabin filter, do so. Mice are looking for warm winter homes now!

 

Some folks have leaks that fill up the area where the 12v battery resides in the passenger side of the rear hatch area of the car.
Check there for water. As well as the same area on the driver's side.