Decades of well-established research have linked nitrogen dioxide, or NO2, to respiratory conditions such as asthma and chronic obstructive pulmonary disease, which especially affect children and older adults. This harmful link is so well established that some states have begun banning gas appliances in new construction. And now a new study has shown in stark detail just how long and far this gas spreads and lingers in a home.
By sampling homes across the U.S., the researchers found that in many, levels of exposure to NO2 can soar above the World Health Organization’s one-hour exposure limit for multiple hours—even in the bedroom that is farthest from the kitchen.
"The concentrations of NO2 we measured from stoves led to dangerous levels down the hall in bedrooms … and they stayed elevated for hours at a time.
Especially the combo microwave units.
A relatively good way to check is if there is a void of unusable cabinet space above the middle of the hood, it could have an exhaust vent; if there are however vents above the hood, it is likely just a filtration type.
I lived briefly in an apartment with an older combo unit. The vent fan would pull in fumes from the stove and eject it out the front above the microwave. If you were a particularly tall person it would spit the exhaust directly into your face while you stood in front of the stove.