alarm
alert
ambulance
attention
background
beacon
beware
bulb
caution
ceiling
concrete
construction
danger
dangerous
dark
dirty
emergency
factory
fire
flash
flasher
glowing
grunge
industrial
industry
interior
lamp
light
night
old
orange
police
protection
red
rescue
rotate
rotating
safe
safety
security
sign
signal
siren
stop
urgency
wall
warn
warning
work
yellow