Firstly, Bahr writes, we should ‘‘design out’’ the hazard
from the system (p. 14). If that is not possible, we should
control the hazard using various fail-safe devices, e.g.,
pressure valves relieving the system of dangerous pressure
build-up (p. 15). When designing out or controlling is not
an option, warning devices (e.g., smoke alarm) and
procedures (e.g., emergency shutdown) and training should
be used (p. 16–7).