Flat or Duct Floor

They all have wood sub-flooring. If you have a reefer with a persistent stink, clean the floor (wire brush or acid wash) and you'll probably find a bunch of pin holes or cracks. Left unrepaired, the trailer has got short time before the sub-floor rots enough to make it unsafe. That is, if you're not already getting rejected for some loads due to odors. If you've seen one where the floor is a little uneven, that's the first sign that the sub-floor is rotting away.