It is made with an airtight container part-filled with different types of chlorine tablet and other reagents.
The reaction produces an expansive increase in pressure, eventually rupturing the container.
Such a device is a more toxic and acidic alternative to a dry ice bomb, but likewise typically made by young people for amusement and recreational use rather than with any intent to harm.
[1] However, exposure to chlorinous gases and the reactive substances involved can cause respiratory problems from inhalation and also cause injury to other mucous membranes, similar to tear gas.
Contrary to the belief of chemical laymen and some public security experts,[2] chlorine is not generated by the reaction of hydrochloric acid with ammonia, but instead ammonium chloride is produced.