air
brown
chemical
chimney
co2
coal
damage
danger
day
dioxide
dirty
electricity
energy
environment
environmental
factory
fog
fuel
fumes
gas
generation
geo
global
grunge
hot
industrial
industry
large
manufacturing
nature
pipe
plant
pollution
power
problem
refinery
risk
safety
saving
sky
smog
smoke
space
station
steam
steel
sun
technology
tower
warming