area

atmosphere

blue

chemical

chimney

city

cityscape

climate

cloud

danger

day

dioxide

dirty

district

ecology

energy

engineering

environment

factory

fog

fumes

gas

global

industrial

industry

landscape

manufacturing

metal

nature

pipe

pipes

plant

pollution

power

process

sky

skynn

smog

smoke

smokestack

smoking

steam

steel

technologic

technology

tower

toxic

tube

warming