INTRO: my basement apartment kitchen is in the middle of a row house with no immediate access to the outside wall for fan exhaust. so i am using a recirculating filter fan (which does not blow outside) above the range to trap grease fumes. however, i also want to have some sort of exhaust solution so i was thinking of a ceiling fan (AKA "fart fan") that blows outside the air pre-filtered for grease fumes that can cause fire hazard through about 12' of 4" ducting.
Q1: in this two-fan solution, since the grease fumes are supposed to be trapped in the filter fan above the range, does the ceiling fan and its exhaust ducting still pose a fire hazard ?
Q2: the 12 ft of ducting is designed to make a total of 3 90 deg bends. does this many bends pose an additonal fire hazard since grease does tend to collect on bends more than in straight duct.
Q3: the fan that i got is Broan 140QTR, which is actually a bathroom fan and the instructions say do not use it in the kitchen area. i could not find a kitchen-rated ceiling fan, all they had were fans with 10' opening that are designed to go outside immediatelty through the wall, not ducting. however, the instructions from the bathroom fan that i got do not consider the fact that i am pre-filtering the fumes for grease so i am wondering if it still might be OK to use it given that circumstance ? i simply could not find a kitchen-rated ceiling fan with a 4 inch opening designed to blow out through ducting.