The 3M® HEPA Mask is the best right now, the filters are P100. Price: $20.24 + $4.05 shipping at Amazon, problem is the filters have to be changed every 8 hours or when you see that you are having a hard time breathing. The filters will set you back Price: $13.37 for two pairs so it is not cheap and is to be used only when things get real bad.
Link to amazon: http://www.amazon.com/3M-7182-3M%C2%AE-HEPA-Mask/dp/B0006FMK0W
I am ordering the A/C filters for inside the house MERV 13 rated at https://filter-monkey.com/index.php?productID=3613
Like 74 said the best way is to stay put in your house if it gets real bad, the A/C filters, stored food and water, have everything inside you house so you do not need to go out. Tape up the windows with duct tape.
This is what will need to happen when we see things get real bad only. Get prepared since we know that they are not telling us the truth.