Exhaust hoods like that are a really bad idea (and actually forbidden in some places) when you have a system which requires open fire like a gas stove, an oven or a gas heating system. They transport air outside and depending on the age of the building not enough fresh air gets in while the fire is consuming all the oxygen.

Also the reason why it is a really bad idea to have a gas heater for warm water and one of the mobile indoor acs. We have some deaths in Vienna every year because of that.

Edit: nevermind, only somewhat true. The slight under pressure caused by exhaust hoods with outside vents pulls down exhaust fumes from the chimney in case of gas heaters. In case of ONLY a gas stove it is not the same problem (I threw them into one basket because most places with a gas stove also have gas heating around here, and in this cases it would be a big no-no).