Contrary to many beliefs, an article from an Ozone blog has me doubting does HEPA air purifiers really work? Technically it only traps airborne particles rather than killing it off.
There are many different types of air cleaner in the market. The keyword you are looking for is HEPA. An air purifier equipped with a genuine True HEPA filter will be able to trap 99.97% of the airborne irritants as small as 0.3 microns. Brands like Blueair can further target allergens down to 0.1 microns while premium brand like IQAir can capture microorganisms 100 times smaller than what a standard HEPA filter would.
So what can a HEPA air purifier remove? Anything that is airborne from hair, dust mites, pet dander, mold, mildew, pollen, bacteria, and virus in the air. For tobacco smoke, odors, and chemical fumes like radon, VOCs, ammonia, CO, a carbon filter is needed instead to properly capture any gas based particles.
One thing to keep in mind that air purifier alone would not be able to get rid of all the pollutants in a room. Regular vacuuming and mopping is a must as dust, allergens that are not airborne will drop to the floor unless it is stirred up. Also, particles that are stuck on the wall or ceiling will remain there until there is a cleaning solution in removing those pollutants.
Going back to the questions, there is a simple reason why we fully endorsed HEPA air purifier rather than an Ozone generator machine. Ozone itself is harmful to our body and long exposure to Ozone will have a negative impact on our health. You need an air purifier to improve indoor air quality, not "generating" more pollutants.
To recap, yes air purifier does work wonders to improve your indoor air quality. This is providing the purifying machine is fitted with a genuine HEPA filter to capture airborne particles as small as 0.3 microns. A carbon filter is also needed to deal with smoke and odor particles.