What air filtration options exist for enclosures? Given the emissions that 3d printing gives off (ABS = styrene and other chemicals, PLA give some off, etc), what options are there to filter the air in the enclosure other than venting the air out of a window?
More information on the chemicals 3d printing emit:

http://built-envi.com/portfolio/ultrafine-particle-emissions-from-3d-printers/

It looks like activated carbon filters would be a strong performer for ABS (styrene) and PLA (lactide):

https://www.sentryair.com/activated-carbon-filter.htm

Are there better filtering materials or processes for filtering the air in an enclosure?
Here's an example filter setup:

This fan mount: https://www.thingiverse.com/thing:780001
60mm fans and this filter: https://www.amazon.com/gp/product/B00XNI5SY4
And sandwich the filter on the fan using this fan grill: https://www.thingiverse.com/thing:11906
My residential materials expert referred me to these links (3D Printing Fume Extraction Solutions, and ABS 3d Printer Nanoparticle and Chemical Exhaust Air Filter) and thinks that you're pretty much on track with the idea of using activated carbon.

We both primarily print with ABS with my Replicator Dual and what's worked enough for me (in the past 5 years) is to keep my printer next to a window or vent in my den at home. The window is obviously a good ventilation option, but the variability that it creates in the ambient temperature screwed with my prints. Later, I moved my machine into its own hutch, which, if it is an option, would greatly help the overall environment for both the machine and any stored filament.

We'll keep poking around, but hopefully that helps in the mean time.