Modern homes present something of a double-edged sword: They tend to be sealed up, keeping out drafts and making the space more energy efficient. But the downside is that a well-sealed home also traps in pet dander, smoke from cooking or fires, dust mites and mold. All of those nasties floating around can trigger respiratory issues like coughs, sneezing or stuffy noses. And just before allergy season really kicks off, you might consider outfitting your living space with an air purifier. They've come a long way in the last few years—nearly all now boast high-efficiency particulate air, or HEPA, filters that are certified to capture the smallest particles that can cause trouble. Herewith, some of the best options to buy right now, based on your individual needs.