Which Air Purifier?

My sickly grandfather will soon be moving into my home with me and my family.  We recently lost my dear grandmother, and we are all he’s got. I have twin toddlers with me at home already, so this seems like the best option. My grandfather, a longtime former cigarette smoker has a lung disease.  That health issue, along with my own young family got me to thinking about my indoor air quality. My husband has always been good about changing the air conditioning filter. He will even hose down the outside HVAC unit in order to keep the heating and cooling unit working well.  But I wonder if that will be enough for our indoor air quality, given the current health of my grandfather? Especially with a dog, a cat and two toddlers making dirty diapers all day long. With pets, children and an elderly family member, I have been seriously looking into an air purification system.  Clean air inside our home is not only necessary for comfort, but of course, essential for life. So I’d like to have a higher indoor air quality for my family. I know air purifiers remove allergens and contaminants from our living space. The air purifiers will actually trap most of the pollen and mold spores and keep them from getting into the circulation and flow of the conditioned air.  The air purifier can virtually keep the contaminants away from my family, which would certainly be my goal. There are so many air purifiers on the market now that I should have no problem getting one, but which air purifier do I get?

air filter