There are literally hundreds of different air purifiers out there on the market today. Many of the best air purifiers with the best hepa air filters go virtually unoticed because of the price. Many people looking to try out an air purifier to help with indoor air quality issues are unwilling to invest much money because they view it as a longshot. They seem to top out at around $200-$400. To get your hands on the best air purifiers, you should really be willing to spend between $700 and $1000. These units will have top of the line hepa air filters that are certified to trap the smallest of particles and will last a relatively long time. They will typically included many pounds of activated carbon for toxic chemicals and odor causing gases. These models will also be able to clean fairly large spaces and will be crafted much better than the cheaper units you can find in stores. I would advise that if an air purifier is what you needs to free you of adverse health symptoms, that you look into the best air purifiers you can afford. It will pay off in the long run.