HuffPost may receive a commission from some purchases made via links on this page. Every item is independently curated by the HuffPost Shopping team. Prices and availability are subject to change. I was surprised to find out that indoor air quality is often worse than the quality of air outside, per the U.S. Environmental Protection Agency (EPA). But it makes sense: Indoor spaces can be replete with pent-up dust, accumulated dander, stagnant pollen and dirt — among other creepy-crawly allergens