BEIJING -- Dealing with smog has become so much a part to daily life in China that it's a regular feature in weather forecasts.
On Monday, while world leaders converge in Paris for a U.N. conference on climate change, the air quality index for Beijing exceeds 500; categorized as officially "beyond index," right above "hazardous."
The World Health Organization says a safe level of airborne particulate matter -- that which the air quality index measures -- is 25 micrograms per cubic meter. That line is crossed so often in cities like Beijing that even a government official called it unbearable.
By 4 p.m. in the capital city on Monday the index hit 608 -- more than 24 times the safe level dictated by the WHO.
The local government issued an orange pollution alert -- only its second highest in a four-tier system, under red. The move requires work at construction sites and factories to halt.
Coal supplies two thirds of China's energy consumption, and the northern half of the country relies on it to heat buildings in winter months.
The issue wasn't fully recognized by China's leaders until 2010, when the U.S. Embassy in Beijing published a tweet calling the air quality readings in Beijing "crazy bad."
The ensuing media coverage pushed it onto the main national stage. Beijing's local government rolled out their own monitoring system and began publishing its findings from 2013.
The grey-brown-yellow sky has become an embarrassment to hide on occasions that shine a spotlight on China's choked capital city.
If there's a silver lining to the thick layer of smog, it has given birth to a host of creative gimmicks, from a bicycle with a filters to canned fresh air.
The government says a cold front will likely push into the area in the middle of this week to help clear the air.
Until then, for Beijingers it's the usual routine: shut the door and wait it out inside.