How big is your office? Just one big room?
If so, do you have furniture that would soak in smoke/other scents? If not, incense (nag champa) is my favorite option.
If so, check out NASA's list of air filtering plants. (http://en.wikipedia.org/wiki/NASA_Clean_Air_Study#Chart_of_air-filtering_plants)
this will help keeping others out..............Show Image(http://pickledeggs.com/wp-content/uploads/2013/12/512hNPsCWL.jpg)
on another note...........believe it or not "dryer sheets" work well depending on how big your office is?
i keep them in my truck and it always smells fresh :cool: