@Ponygurl @Sartori Let's not get caught in the bramble of misunderstanding.

I'm simply pretending that neither the book nor the movie exist. Come February 14, I'll be avoiding the television, walking away from numerous conversations, and wearing noise-canceling headphones in public.

I suppose I'll add showing up to movies after the trailers to my list. Thanks for the reminder.

Urban_Tribesman said:

Sounds like the external ground level is too high allowing dampness outside to penetrate the wall which, I would guess, is a solid wall not a cavity. That would be the cause of your efflorescence.
Do you, by any chance, go down a step into the 'office'? I wonder if the room once had a raised timber floor that has been removed in the past, resulting in this stump to cover the air brick.
I still think the most likely reason for the 'stump' is to turn the air flow from the air brick down to a lower level, hence the question about the cellar.
Can you see through the air brick from outside? Use a torch to see if you can see anything. I doubt there is a water or gas main as Satori has suggested as these would be obvious externally. Do you even have gas? Where do these (gas/water) come into the house? If somewhere else, then they won't be here as well.
Ideally, your external ground level will be 150mm below the internal floor level to prevent the ingress of damp. People mistakenly raise external levels all the time and cause damp issues inside, so worth looking at.
Have you got access to some net curtain wire? If so, get 3 or 4 foot and fish it through the air brick and see if it keeps going in, which would suggest it is passing down to a lower level.
Still,waiting for @Appy61 to comment. Where are you in the country BTW?

Hey. I haven't forgotten about this btw. just needed time to examine it properly via your questions. strange thing. the lounge before you go in is floorboards then you go into the office/understairs and thats concrete, totally level with the lounge. 

Sartori said:

cookiee_munster said:

the lounge before you go in is floorboards then you go into the office/understairs and thats concrete, totally level with the lounge

Did the previous owner watch a lot of Brookside ? ;)

oh, god don't. lol. i have a thing with really old houses and "brutal history" lol

Haha, you're terrible iuv. The whole thought of torture though..Man's brain seriously needs to be re-wired.

Discussed this with @Appy61 over the weekend. We are of the opinion that the crown ( the curved top bit) it a mortar cap to rendered brickwork below. I still think it is most likely to be some form of vent, hence the air brick outside. Have a really good, close look around it and if this looks like the case, get a bolster (wide blunt bricklayers chisel) and a hammer and gently nibble away at the top on the edge/corner to expose what is underneath.
Interesting that you say other parts of the house are suspended timber, as these will need ventilating, so you will have other air bricks around the perimeter of the house. It could be that this solid part of floor was timber and was replaced with concrete because it had gone rotten. Strange that the air brick is not far above the external ground level the other side of this stump. If it was timber at one time, it would need ventilating otherwise it would rot eventually, which further suggests this is/was channeling air from the air brick to below the floor. By any chance, is the floor level the other side of this area lower? If so, an air brick there would be able to cross ventilate the floor using the 'stump' to ventilate the air out the other side.
This is getting a bit heavy. More pictures would help showing the outside.

It's not pink.