air
blue
brown
building
carbon
chemical
chimney
color
construction
danger
dioxide
dirty
electricity
energy
environment
environmental
factory
fog
fuel
fumes
gas
generation
global
grunge
industrial
industry
large
light
manufacturing
nature
outdoors
pipe
plant
pollution
power
safety
silhouette
sky
smog
smoke
station
steam
sun
sunrise
sunset
technology
tower
warming
winter
yellow