blue

business

chemical

chemistry

chimney

construction

crane

diesel

drilling

energy

engineering

environment

equipment

factory

fossil

fuel

gas

gasoline

heavy

industrial

industry

machine

machinery

manufacturing

metal

oil

petrol

petroleum

pipe

pipeline

plant

pollution

power

production

refinery

resource

rig

sky

smoke

station

steel

storage

structure

tank

technology

tower

tube

water

well