In order to stay healthy we must keep ourselves safe from exposure to harmful chemicals, toxins and known carcinogens. There are 3 ways that the human body can be affected by those elements, they are absorption, ingestion and breathing them in. Ingestion is the simplest one to control, simply know what you are eating. Absorption can be limited to wearing protective clothing when around or working with harmful elements. Breathing or inhalation is another matter entirely.
Often we are not told if there is something harmful in the air we breath. That is evident with all of those ads on TV for Mesothelioma cancer attorneys. Someone did not inform them of the asbestos in the air. But asbestos is just one of many elements that can cause problems. Indoor air can be very toxic if there is no fresh air circulation in the room. Toxins are given off by the foam in cushions, couches and even that brand new bed mattress.
You can use air purifiers and filters all you want but the best solution is good old fresh air, so open a window.