機器
alert
alertness
attention
avoid
background
beware
black
careful
caution
chrome
cog
cogwheel
equipment
first
gear
gearwheel
instruction
machinery
mechanics
mechanism
metal
metallic
nickel
precaution
prevent
prevention
procedures
production
proper
protect
protection
protective
regulation
risk
safe
safety
safety first
scratch
security
steel
symbol
tool
unsafe
warn
wheel