Bless the Yanks and their hourly air quality report from the Embassy in Chaoyang. I have their App on my iPhone.
from: http://www.wunderground.com/health/pm.asp
US EPA (http://www.epa.gov/pmdesignations/faq.htm):
Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. Particles can be suspended in the air for long periods of time. Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with an electron microscope.
Many manmade and natural sources emit PM directly or emit other pollutants that react in the atmosphere to form PM. These solid and liquid particles come in a wide range of sizes.
Particles less than 10 micrometers in diameter (PM10) pose a health concern because they can be inhaled into and accumulate in the respiratory system. Particles less than 2.5 micrometers in diameter (PM2.5) are referred to as “fine” particles and are believed to pose the greatest health risks. Because of their small size (approximately 1/30th the average width of a human hair), fine particles can lodge deeply into the lungs.
around noon Sat 22 October
around 6.30pm Sat 22 October
Maybe today is an indoor day?
The PM’s can and will drift into your room!