air
breath
breathe
brown
building
chimney
co2
danger
dioxide
dirty
electricity
energy
environment
environmental
factory
fog
fumes
gas
generation
geo
global
grunge
hot
industrial
industry
large
manufacturing
nature
ozone
pipe
plant
poison
pollute
pollution
power
problem
risk
safety
saving
sky
smog
smoke
stack
station
steam
steel
sun
technology
tower
warming