Cooling fan for electronics cabinet

I prefer to use fans as intakes, not exhausts & put filters on them. Then you have some airflow to cool the unit, minimal to no dust to clog the inner workings and act like a blanket on heat sinks, and with the filters external, when they turn from black to grey it is time to remove and rinse them off and reinstall them. In fusty areas you may need to clean them 2 times a week, in clean areas monthly. Before anyone complains about cleaning filters, external filters take less then 2 minutes to R&R, digging into a cabinet and blowing out the dust takes far longer, and there is no easy way to know when it needs to be dome.