Kitchens – Should the chimney cooker hood have a flue

In rural locations in the US, propane is often used as a fuel for cooking and heating. The gas is stored in an outdoor tank and piped into the house. Propane burns hotter than methane ("natural gas"). Therefore you may need a special stove to use propane, and if you want to hook up appliances such as a water heater or clothes dryer, you will definitely need models designed for propane.

Piping for gas is a high-stakes job: if you mess it up the odds of it killing or hurting you are significant. Your local law almost certainly requires that only licensed professionals work on gas lines for this reason. With propane, there may also be special ventilation or safety system requirements. So for all these reasons you should start by calling some vendors/installers and asking for proposals from them. You want to figure out whatever is common in your area, and do that -- sticking with whatever's common will make it easier to shop around for fuel deliveries and repairs, and doing something unusual or amateur around gas lines is a sure way to scare off potential buyers if you ever sell your house. In fact, if your system wasn't installed professionally and passed government inspection, I'd be surprised if anyone would even sell you fuel.

So although this is the DIY stackexchange, some jobs are really only for professionals. Get recommendations from neighbors and call around.

In general, yes an exhaust vent (or any vent) can turn corners. But there are many other factors to consider.

Different vent materials or dimensions resist air differently. Different ways of turning corners resist air differently. The best place to start looking for info on this is the vent installation manual. It will talk about different ways to construct vents, what types of ducting corners can be used, and what size of ducting you need. It will talk about how many feet of vent the blower can push through, and how many feet to count a corner as (typically 5').

So you know, the shallow box vents have poor airflow. And you have to consider getting through the top-plate of the wall, which would create a huge weak point. When we built our kitchen I was hoping for in-wall ducting. Instead, the installers had to put a 10" circular duct up through the middle of the cabinet above the stove.