alarm
alert
background
banner
beware
button
caution
city
danger
dangerous
death
electricity
electroshock
energy
enter
entry
hazard
high
icon
industrial
insignia
isolated
keep
label
lighting
lightning
mortal
notice
placard
poison
power
risk
safety
security
shock
sign
signboard
skeleton
skull
stop
street
symbol
toxic
urban
virus
voltage
warning
yellow