Meteorological conditions causing CO poisoning event in March 2009 in Ji’nan, Shandong province

A serious CO poisoning event happened on March 14-19, 2009 in Ji’nan, Shandong province. 78 people were poisoned in this event and the symptom of most sufferers appear during the night of March 15 to the early morning of March 16, and it is fulminant. Weather conditions, air mass property and meteorological elements were analyzed during this CO poisoning event. The results indicate that after a cold air process, it turns abnormally to warm, then the poisoning event happens. The air mass is dry and warm, and atmospheric stratification in the middle and low layers is stable. Air temperature increases obviously and air pressure descends. The period of weak wind speed is coincident with the period that the poisoned people increase sharply. The meteorological conditions causing this event are various. Warm ridge in 500 hPa moves to the east and develops, and then it controls Ji’nan region with the northwest dry air mass. Thus, the local air temperature and air pressure change strongly, and air density depresses significantly. It influences the natural ventilation of room and the pumping effect of chimney and results in CO poisoning event. The weak wind and low density air mass are the main reasons increasing poisoned people rapidly in night.