| MERV | Minimum particle size | Typical controlled contaminant | Typical application |
|---|---|---|---|
| 1–4 | > 10.0 μm | Pollen, dust mites, cockroach debris, sanding dust, spray paint dust, textile fibers, carpet fibers | Residential window A-C units |
| 5–8 | 10.0–3.0 μm ("E3") | Mold spores, dust mite debris, cat and dog dander, hair spray, fabric protector, dusting aids, pudding mix | Better residential, general commercial, industrial workspaces |
| 9–12 | 3.0–1.0 μm ("E2") | Legionella, humidifier dust, lead dust, milled flour, auto emission particulates, nebulizer droplets | Superior residential, better commercial, hospital laboratories |
| 13–16 | 1.0–0.3 μm ("E1") | Bacteria, droplet nuclei (sneeze), cooking oil, most smoke and insecticide dust, most face powder, most paint pigments | Hospital and general surgery |
Whilst size comparisons between viruses and bacteria can be useful to researchers, it is also useful to compare the size of SARS-CoV-2 to other things that are encountered daily. For example, a dust mite is typically 200 µm in size. If we take a 100 nm SARS-CoV-2 particle, this makes the dust mite 2000 times larger.
