If rectangular ducting please note.
Can all over the range microwaves vent outside.
Microwaves over the range otr typically vent in two different ways.
Microwaves that vent to the outside force the air through duct work to the outdoors.
When considering venting in an over the range microwave there are ducted vents and recirculating vents.
This eliminates smoke cooking odors moisture and hot air from remaining in the kitchen.
All over the range spacemaker microwaves can be vented to the outside using an equivalent total of 140 feet of rigid 3 1 4 x 10 rectangular or rigid 6 round ducting.
Remove the access plate on the top of the unit in order to reach the motor.
Ultimately the goal of the vent is to pull the air from the microwave and deposit it to the outside.
Many times an over the range microwave that recirculates cooking fumes can be converted to exhaust to the outside.
If you have an over the range microwave it should have an exhaust fan that vents to the outdoors.
After the smoke and steam are removed the filtered fan vents the air outside your home or cleans it before releasing it back into the kitchen.
Typically there might be a cabinet installed over the microwave and inside that cabinet will be duct work or a soffit above the microwave or a direct wall exhaust.
Over the range microwaves can vent to the outside or can recirculate the air.
Over the range microwaves have a light and fan built into the bottom of the appliance.
Microwaves are shipped from the factory to vent out the top vertically but can also be vented out the rear horizontally.