air
atmosphere
background
carbon
chemical
chimney
climate
co2
coal
contamination
danger
dioxide
dirty
ecology
electricity
emission
energy
exhaust
factory
fog
fuel
fumes
future
gas
global
harm
industrial
industry
manufacturing
nature
pipe
plant
pollution
power
problem
production
refinery
sky
smog
smoke
station
steam
steel
sun
technology
tower
toxic
vapor
warming