When smell particles diffuse across a room, what other particles could get in the way?

Question: When smell particles diffuse across a room, what other particles could get in the way?
- Keywords:
  diffuse,
  particle,
  sense,
  smell
Asked by aka Agent Jellybean to Anna, Hayley, Iain, Rebecca on 23 Jun 2015.
- Iain Bethune answered on 23 Jun 2015:
  
  Molecules that cause smell are usually small, for example the ‘rotten egg’ smell is caused my Sulphur Dioxide (SO2). These molecules can bump into any of the molecules that make up air (mainly Nitrogen, Oxygen, and some Carbon Dioxide and Noble gases), as well as dust particles that might be suspended in the air.

Question: When smell particles diffuse across a room, what other particles could get in the way?