air
atmosphere
blue
chemical
chemistry
chimney
climate
contamination
dioxide
ecology
electricity
emission
energy
engineering
environment
environmental
equipment
factory
fuel
gas
generation
global
heat
heavy
industrial
industry
manufacture
manufacturing
nature
oxygen
petroleum
pipe
poisoning
pollution
refinery
resource
scenery
sky
smog
smoke
tall
technologic
technology
tower
toxic
tube
warming
waste