air

atmosphere

blue

carbon

chemical

chimney

city

climate

cloud

condensation

damage

danger

day

dioxide

dirty

ecology

emission

energy

environment

environmental

exhaust

factory

fog

fossil

fumes

gas

global

heat

high

industrial

industry

manufacturing

nature

outdoors

pipe

plant

pollution

polution

power

sky

smog

smoke

steam

substance

technology

toxic

vapor

warming

white

wind