As per the US Environmental Protection Agency (EPA), our indoor air quality can be 5X times more contaminated than the air outdoor. Our homes are enclosed by walls, windows, and doors. The inner air does not get enough space to circulate properly and so our homes have higher chances to accumulate pollutants and dust. This may cause diseases related to the respiratory tract and neurological problems.
Other than that, pollen, pet dander, paint fumes, dust mites, smoke from tobacco or...