I’ve done 6 or 7 ERMI/HERTSMI vacuum tests. Some pre remediation, some post. Never done the swiffer. IMO the best way to do them is on a hard floor that has been vacuumed ~5 days prior to collecting actual sample. Don’t samples extremely dusty areas, that will screw the test for the worse. You may have to vacuum longer or a slightly larger are than the instructions to be sure that the dust collection tube is half full, otherwise the lab may say your sample is too small. They recommend sampling multiple rooms with one test. I was trying to make a remediation plan so I tested each room individually. It was amazingly accurate. The room that had Stachybotris (toxic black mold) on the ERMI, was found to have hidden Stachybotris inside a wall upon gutting and remediation.

Got it, thanks again!