Not all vacuums are created equal when it comes to the removal of microparticles. Things like pet dander or outdoor allergens might be sucked up, but without a filtering system they return to your home via the air expelled from the vacuuming process. If you have pets on the carpets or lots of sports gear lying around, you might also have strong smells to contend with. Many vacuums today come with HEPA-rated filters, which means they should clean the air down to the microparticle level. Some include branded air fresheners too. These filters may be washable or replaceable.