英文關鍵字
air
away
behind
black
boiler
building
chimney
coal
dirt
ecology
emission
environment
firing
flue
fly
flying
gray
heat
high
house
industrial
industry
iron
lot
metal
outdoor
pipe
plant
pollution
power
roof
sky
smoke
snow
soot
steam
steel
stove
stovepipe
technology
thermal
tube
village
winter