CITROEN C5 2011 Owner's Handbook Manual page 110

Passenger airbag OFF
VII
! To assure the safety of your child, you must deactivate the passenger's
front airbag when you install a child seat in the rearwards facing position
on the front passenger's seat.
Otherwise, there is a risk that the child could be seriously injured or killed
if the airbag were deployed.
108
C H I L D S A F E T Y
Refer to the advice given on the label
present on both sides of the passenger's
sun visor.