Your microwave is also your range hood. Which way it vents changes how well it clears steam, smoke and grease.
An over-the-range microwave does two jobs, and the second one — extracting cooking air — is the one most people never think about until the kitchen fills with smoke. Every OTR unit can be configured to vent one of three ways, and the difference is significant.
The three configurations
- Recirculating: air passes through a charcoal filter and returns to the room. No ductwork needed, and it removes odour and some grease but no heat or moisture.
- Vertical duct: air goes up through the cabinet and out through the roof or an upper wall. The most effective option.
- Horizontal duct: air exits straight back through the exterior wall. Also effective, and common in older homes.
Getting it wrong
The blower has to be physically rotated to match the configuration, and the exhaust damper has to be fitted correctly. We regularly find units installed with the blower still in the factory recirculating position while a perfectly good duct sits behind the wall doing nothing.
“If steam from a boiling pot fogs your upper cabinets, your microwave is almost certainly recirculating when it could be ducting.”
Filter maintenance
Metal grease filters go in the dishwasher every one to two months. Charcoal filters cannot be cleaned — they are replaced every six to twelve months, and an old one badly restricts airflow and makes the fan noticeably louder.