[dredmorbius]

Bad advice.

A decent filter's throughput is going to be multiples of your structure's air-exchange rate.

What you want to do is to filter the interior air, by passing it, multiple times, through the filter. If you put the fan and filter in a window, you're hugely multiplying the air-exchange rate (to no net benefit), but are filtering that air only once.

The net result is a much higher indoor particulates level.

So no, don't do this.

[spookthesunset]

Interesting perspective. Wouldn’t it be best to do some combo of both? A low volume fan/filter that maintains positive pressure and an internal filter/fan combo?

I mean in labs and manufacturing facilities that need ultra pure air, I’m pretty sure they maintain a positive pressure inside the sensitive areas. Otherwise you’ll be sucking in bad crap from every nook and cranny...

[dredmorbius]

Various lab setups have different requirements.

For biocontainment you generally want negative pressure, such that all exhaust is filtered.

For clean rooms, positive pressure, to ensure filtration and minimum particle reduction levels within the conditioned space. These also have staged zones, much like a cascade refrigerator, with finer levels of purity as you approach the core. Humans themselves are excluded from the higher-purity zones (we're leaky bags of flakey skin, hair, dander, sweat, and mucus). Most especially in chip-fab, but also I suspect various nanofab facilities.

All of which is pretty much entirely outside my paygrade, so I can't really comment intelligently.