air
brown
building
chimney
co2
color
danger
dioxide
dirty
electricity
energy
environment
environmental
factory
fog
fumes
gas
generation
geo
global
grunge
hot
industrial
industry
large
manufacturing
nature
orange
outdoors
pipe
plant
pollution
power
problem
risk
safety
saturated
saving
sky
smog
smoke
station
steam
steel
sun
sunset
technology
tecnology
tower
warming