How many holes can you put in block wall

At the local Girl Scout campground is a nice building with a huge fireplace in the middle. The floor framing runs from the foundation of the fireplace to the block foundation wall around the perimeter.
I am told that the block wall was added much later than the building was built, but no one if very clear how long ago that might have been.
If the wall was added later, then whatever was holding the building up before was removed completely.
Anyway, there are only three vents in the crawlspace, each in the middle of a wall and in the middle of the fourth wall is the access to the crawl. The wood floor above has done a lot of buckling.
Yes, I know that covering the crawl floor is a good idea, but this is a lightly used structure, is not heated all winter, certainly has no AC, etc. Seems like most camp structures I see have a very open crawl space and I suspect that should have been the case here.
I know I can find out how many vents there should be, but if someone wants to tell me that, I’m listening. The building is about 20×20.
But this got me thinking…what is the rule on how many block one can remove from a wall without unduly compromising the strength of the wall????
Rich Beckman
Another day, another tool.
Replies
If blocks are filled, remove all you want, but around here its county code to not have any vents in the crawl space. They want it tight. with vapor barroer on ground.