access
air
area
authorized
closed
co2
conditioner
confine
confined
construction
danger
death
enter
entry
environment
file
flow
gas
halon
hazard
health
hole
icon
industrial
inhale
label
manhole
only
permit
protect
protection
protective
risk
rope
safety
security
set
sign
space
sticker
surface
symbol
tunnel
ventilate
ventilation
warning
water
work
zone