What is this exterior vent below window?

[MrsTopaz]

Does anyone know what exterior vent is for? It was here when we moved in. None of the other houses in our row have it. That particular room seems to have a musky smell that I can’t locate. The other side of it is a panel in the interior wall-like a blank board. It sits behind the radiator. I’ve found mould on the interior panel and have tried to clean it but it’s really hard behind the radiator. I’ve never taken a radiator off before to have a good look. Plumber could take it off for me I’m sure but then which tradesperson after that for the vent? Many thanks

What room is below?
My first thought was a vent for a cooker hood from the kitchen

If kitchen is below then I think thats what it is. Maybe put cooker hood fan on and listen if you can hear from outside

It does seem rather high up but may be a simple reason for it

Boiler vent?

Below this room is a garage that been turned into an office. I don’t think it’s connected to the kitchen as this is at the back of the house on the other side. The boiler box is in the kitchen, there is an airing cupboard upstairs but this is sandwiched between the two other rooms connecting wall.
The room it’s in is the box room of the house, so maybe previous owners had a tumble dryer or something that would connect to it? I’ll need to take the radiator off I think.

Looks like a boiler vent, maybe the boiler used to be in that room.

Could be a left over vent from gas wall heater now replaced with radiator

I left one as neater than trying to brick it up

Wait till you or one of the neighbours have 3 or 4 of the same bricks ( usually removed during building work) and remove it and replace the bricks. It easy to do. That vent looks awful.

Agreed, I would say that is exactly what is is

Very popular in the 70's & early 80's. They were ok but inefficient as each heater only heated the local area plus it meant you had multiple gas pipes all over the property.
When I bought my first house in 1986 it had three of them. One in the living room, another in the kitchen and a third on the first floor landing. Each had a similar external vent which at ground level is usually covered by a metal guard (looks like a kitchen strainer!).

Thank you for all the replies, these are really helpful. Will see if I can have it removed and assess what’s going on behind the radiator.

Boiler vent for a removed boiler