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Umluft f =
gen.	air circulation; circulating air
chem.	forced air; recirculating air
construct.	air recirculation
earth.sc., transp., met.	convection
mining.	circulating air (Sichter)
nat.res.	recycling air
refrig.	recirculated air
tech.	return air; circulated air
Umlüfter f
tech., industr., construct.	air circulator

Umluft: 4 phrases in 4 subjects

Chemistry	1
General	1
Technology	1
Transport	1