For all the good they do, airbags are dangerous. They're small, controlled explosions that operate on scales of milliseconds, and if something goes wrong, there's a load of energy that will get released in a bad way. That's why you should always pay attention to airbag-related recalls, like the one Toyota just issued.
Toyota is recalling some 1.4 million vehicles around the world, about 500,000 of which are located in the US. The recall covers the 2010-2012 Toyota Prius and Prius Plug-In, as well as the 2012 Lexus CT 200h hatchback. The vehicles in question were produced between October 2008 and April 2012.
The issue lies with the curtain shield airbag, which inflate around the windows. Some inflators have a crack in the weld that joins two parts of the assembly, and if the parts are separated when the airbag deploys, two things could happen -- either the airbag only partially inflates, or the inflator itself could enter the vehicle. This tends to happen with vehicles that have been left unattended for long periods of time.
Toyota will not be replacing the curtain airbag assemblies. Rather, it will install brackets on the inflators that prevent the parts from making their way inside the vehicle during deployment. Toyota will mail notices to all affected owners.