I think activated carbon filters will work, also mentioned by Abolt.

there was a thread a couple of months on the same question called "reducing stink" have a looky at that.

i should have provided a link, sorry dude.

but you will find it with ease, it was in chems $ equip"

hope that helps

This seems on topic.
I've thought about a gaseous odour reducer and chemical neutraliser to flush through the extractor fans to remove anything residual from ANY reactions.
Is this feasible? What could be used?

Here are some excellent links on the construction, and use, of a fume hood.

http://www.northwestern.edu/research-safety/labsafe/hoods/

http://offices.colgate.edu/chemmgt/fumehoodvalprog.htm

Incorporating an Activated Carbon filter, or series of filters, is probably the best way to go for the substances you mentioned. Along with a powerful fan, forcing the fumes quickly through it.

Check out this chart.

In this chart, 1 is poor and 4 is excellent

http://www.allerairpurifiers.com/pdf/chem_gas_table.pdf

Ozone has it's problems in a small workspace. Ozone can be dangerous stuff and the UV light that is used in the Ozone machines I have seen can cause blindness, if looked at too long.

http://www.hc-sc.gc.ca/english/protection/warnings/1999/99_62e.htm