Consider purchasing a portable air purifier, with a HEPA filter to be used in the case of an emergency to help remove contaminants from the room in which you are sheltering. These highly efficient filters have small sieves that can capture very tiny particles, including some biological agents. Once trapped within a HEPA filter the contaminants are neutralized and prevented from entering your body and making your sick.
Be advised – While these filters are excellent at eliminating dander, dust, molds, smoke, biological agents and other contaminants, they are ineffective against chemical gases.