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If the hood is used in its recirculation mode, it will operate simply
and safely in the above conditions without the need for any of the
aforementioned measures.
The ducting must be fire retardant, 120mm in diameter and the
length should be no more than:
3 metres with one 90 degree bend
2 metres with two 90 degree bends
Bends of more than 90 degrees will reduce the efficiency of the hood
and reduce the airflow.
Failure to observe these basic instructions will drastically reduce the
performance and increase the noise levels of the extractor hood.