Fireworks unleashed sound and colour across China at the start of the Lunar New Year, but also something else - pollution.
A new monitoring index revealed a dramatic increase in fine particles in the air in the first hours of the Year of the Dragon.
The figures tailed off only after 0600, when revellers presumably went to bed.
The data comes from an index that Beijing city government began publishing only on Saturday.
The PM2.5 index measures air particles that are less than 2.5 micrometres in size.
Up until a few days ago the city authorities were only releasing information using the PM10 index, which measures slightly larger particles.