As a user rather than an HVAC engineer, our facility had a lot of local exhaust ventilation on the manual soldering lines, automated reflow soldering and solvent wash (perhaps less common these days), and similar areas. As a result the makeup air flow was pretty high, although demand on the intake heaters was moderated by the heat output from the process which would otherwise have required cooling. As I remember it - from a good few years ago - the air filtration plant worked hard and required a fair bit of maintenance, although the detail of whether that was recirculation or fresh air intake filtration now escapes me.
