When a campfire is below non-full blocks such as carpets, stairs, slabs, trapdoors, and brewing stands, the smoke particles it emits behave in different and inconsistent ways depending on how the blocks are arranged. Specifically, the smoke will:

• Pass through a non-full block immediately above the campfire, if the block above the non-full block is air.
• Be stopped by a non-full block immediately above the campfire, if the block above that is another non-full block.
• Be stopped by a non-full block somewhere above another non-full block immediately above the campfire.

It's easier to see the inconsistencies in a screenshot:

Steps to reproduce:

1. Open the attached world "Campfire smoke.mcworld", or recreate one of the configurations in the screenshot.
2. Experiment with various arrangements of non-full blocks above the campfire and observe how the smoke particles behave.

Expected results:
Smoke particles emitted by a campfire should pass through any number of non-full blocks above them without being affected.

Observed results:
The smoke particles will only pass through one non-full block, and only if it's immediately above the campfire and there are no other non-full blocks above it. It's as if the rule for creating a smoke particle in the block above the campfire is that the block above it must not be a full-size solid block and must have air above it, while the rule for propagating a smoke particle upward is that the block above it must be air.