[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.