  We study the evacuation process from a smoky room by means of experiments and
simulations. People in a dark or smoky room are mimicked by ``blind'' students
wearing eye masks. The evacuation of the disoriented students from the room is
observed by video cameras, and the escape time of each student is measured. We
find that the disoriented students exhibit a distinctly different behavior
compared with a situation in which people can see and orient themselves. Our
experimental results are reproduced by an extended lattice gas model taking
into account the empirically observed behavior. Our particular focus is on the
mean value and distribution of escape times. For a large number of people in
the room, the escape time distribution is wide because of jamming.
Surprisingly, adding more exits does not improve the situation in the expected
way, since most people use the exit that is discovered first, which may be
viewed as ``herding effect'' based on accoustic interactions. Moreover, the
average escape time becomes minimal for a certain finite number of people in
the dark or smoky room. These non-linear effects have practical implications
for emergency evacuation and the planning of safer buildings.
