Smell

Smells are from molecules in the air.
The sense of smell goes directly to the brains emotional center, the limbic system. No interpretation or thinking needed like in our other senses.
http://www.bbc.co.uk/science/humanbody/body/factfiles/smell/smell_animation.shtml

Bad smells affect the mind. "Bad" being unwanted and  worse if the person is unable to leave the area that has the source.

Hospital workers need the best clean air systems to keep sane and do the best job possible in that difficult environment.
I imagine a powerful suction device near patient beds to remove "bad" air, and a fresh air supply to replace the suctioned air. "Worst Smells In The Hospital? There's a List For That!" http://thehappyhospitalist.blogspot.ca/2013/10/List-of-Worst-Smells-In-The-Hospital.html

The smell of dog feces probably contributed to this recent murder in my area.
"Man charged with murder after dog poop dispute"  http://cnews.canoe.com/CNEWS/Crime/2011/09/09/18662206.html
Sentencing http://globalnews.ca/news/387468/ddo-man-sentenced-to-life-in-prison-for-stabbing-a-woman-over-dog-waste/

 Navy battles mould in frigate ventilation systems
".... documents and videos obtained by CBC News show not only mould-crusted vents, filters, ducts and even food stores, but also serious safety hazards resulting from an extraordinary buildup of condensation, which spills and splashes over electrical panels." http://www.cbc.ca/news/politics/canadian-frigates-mouldy-1.3685779

"Animal rendering plant causing horrible smell, RDP resident says" http://www.cbc.ca/news/canada/montreal/sanimax-smell-rdp-1.3668726

"Huntingdon area residents fed up with wastewater stench"  http://www.cbc.ca/news/canada/montreal/huntingdon-wastewater-stink-petition-1.3667866