[lend000]

Love coming to HN and learning from the in-depth research of others on topics like these.

How important do you think the external fan is? (versus just placing it next to the modest airflow of a HEPA filter, as a sibling commenter suggested)

[runnerup]

Very important. “Non-ducted” suction doesn’t have enough static pressure to pull air through a carbon filter, will pull the air around it instead. In electrical terms, this would be like feeding a power sink with a large gauge copper wire and a medium resistance resistor in parallel. 0.01% of the electricity will pull through the resistor, 99.9% will come through the bare copper wire.