air
air pollution
atmosphere
blue
chemical
chimney
clean
contamination
damage
danger
dangerous
detrimental
dioxide
ecology
electricity
emission
energy
environmental
factory
fume
fumes
furnace
gas
global pollution
global warming
greenhouse effect
heating
horizontal
industry
kyoto
outdoors
oxygen
petrochemical
pipe
pollution
sky
smog
smoke
smokestack
smoky
toxic
warm
white
wind