How to Stop Cold Air Entering Through Kitchen Hood Duct with 100mm L-Shaped Pipe?

Hello. Let me explain the situation: the hood above the induction hob is connected with a 100mm pipe, which is led outside the building - then something like a chimney is made, i.e. the aforementioned pipe comes out of the building, then there is an elbow and the pipe goes further up some 40cm ( it is L-shaped). It is all finished with a "hat" with holes. My problem is that I don't know if this is the correct connection because I get cold air from the outside into the apartment. Is there any way to remedy this?

You need to improve the draft by lengthening the chimney.

Fighting the forces of nature is a difficult matter and since the outlet does not close automatically after turning off the fan, the cold air intake with tight windows - especially in winter - is unavoidable-, the installation of blinds that would open the fan looks "thin" due to its power.
There are caps with very low resistance, but this is for sewage systems, maybe you should look for a solution here or such caps for ventilation ducts, something in the shape of the letter "H", which will prevent air from entering from the outside - just one more thing - with tight and closed windows and if in the apartment there is a gas, instantaneous water heater often called "junkers" you can expect the flow of cold air into the room during the work of the junker - as he needs air to burn gas and he will draw it from wherever he can!! and the hydraulic ones, which prevent venting of the sewage system, are really tight - you need to think about it taking the described welds into account.

https://obrazki.elektroda.pl/54_1231481772.jpg

Can you give me a link to a website that has something like this?

How to have tight windows in the house:
firstly there is NO ventilation AT ALL
secondly, if there is a gas boiler, the inhabitants may be asphyxiated

I don't have a gas boiler in my apartment (it's in the basement). I don't think you quite understand what I mean. very cold air from outside enters my house through the hood, which makes it cold in the kitchen. I know that the house must be ventilated, that's understandable. I don't want air to enter the house through the hood.

Use a grommet. I don't know what it's called professionally, but it's a pipe with a movable flap. If it's well made, it will definitely pass the exam

I have a similar problem with the hood. The whole house is powered by electricity, legalet heating + a temporarily inoperative recuperator, but that's a different problem. cold air, which affects everyone this winter. Please help me what and where to install to avoid this phenomenon. Of course, I use the extractor when it is necessary, e.g. but unfortunately it doesn't have the best cooking smells Then the lift is turned off, but the cold comes in. I know that I can count on big heads for which I thank you

In fact, if there is mechanical ventilation with recovery, such connection of the hood should not take place. It should be connected to an air handling unit (through a grease filter of course) and preferably not have its own motor at all, and you can turn up the ventilation to the maximum when cooking.
Combinations for the hood+vent system. in one house are described in detail here: http://forum.muratordom.pl/rekuperator-a-okap-w-kuchni,t89627.htm?highlight=okap . Particular attention should be paid to adam_mk's posts.

In the kitchen, I installed an Akpo hood in which the manufacturer installed a blind. It opens automatically when the fan starts and closes when it stops. I myself had a problem with the influx of cold air through the roof fireplace. In my case, the improvement of the chimney draught was impossible to implement (aesthetic reasons of the building). This is probably the best solution.