air
atmosphere
blue
building
chemical
chemistry
chimney
contamination
damage
dioxide
dirty
ecology
emissions
energy
environment
environmental
exhaust
factory
fuel
fumes
gas
global
greenhouse
high
horizontal
industrial
industry
manufacturing
nature
outdoors
pipe
plant
polluting
pollution
power
refinery
sky
smog
smoke
smokestack
stack
steam
structure
technology
tower
toxic
vapor
warming
waste
white