Particulate matter measuring below two and one half microns in diameter and are referred to as "fine" particles. When a large concentration of these particles are inhaled, it may pose potential health risks. For example, if you are exposed to a large concentration of PM2.5 you may experience coughing, sneezing, running nose or shortness of breath.
During periods of air stagnation, when little wind or air mixing occurs, particle counts outdoors can be higher and the air may appear hazy or foggy. Sources of this particle pollution outside may include vehicle exhaust, construction equipment, burning fuels, smoke and gases produced from power plants. Inside your home, sources can include the following: chemicals from redecoration or new construction, paint, new furniture, tobacco smoke, cooking odors, dust from air condition systems, fireplace smoke, fuel-burning space heaters or even simply burning candles. It is also important to keep in mind smaller particle pollution may travel long distances, sometimes hundreds of miles.