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All answers having "Vent" as clue:

4 Character Answers:

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AIRH

DUCT

EMIT

FLUE

RANT

SLIT

SPEW



5 Character Answers:

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ERUPT

TOKEN



6 Character Answers:

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AERATE

AIRWAY

OUTGAS

OUTLET

UNLOAD



7 Character Answers:

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AIRHOLE

OPENING

ORIFICE

POUROUT



8 Character Answers:

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LETLOOSE



12 Character Answers:

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BLOWOFFSTEAM