I have a hidden room in my house that I would like to turn into a closet. The room (currently only accessible from the outside through the vent) vents the utility room to the outside. I'm not sure why it was designed this way, other than maybe because it was easy since it was already framed for a door. Since I'm going to turn it into a closet I need to change the location of the vent. There's plenty of room between the vent and the utility room to change the location. My problem is that the outside wall is cinder block. What tool would be recommended or is best to use to cut or hammer through cinder block?
Since concrete blocks are fairly thick, I'd drill several holes along the line you want to cut with a masonry bit, then use a use a mini jack hammer such as a small DeWalt with a 1/2" chisel bit. The hole will not be perfect shape etc, so you will need to fill around the vent after installed with some mortar. The pilot holes will help keep the hole in a rough shape and avoid breaking off large pieces of the block. Even it some block breaks, you can fix it up after with the mortar mix.
To do it right, you're going to need a specialized saw, possibly with water cooling. Otherwise the blade just melts. These blades are not cheap, so you need to protect them with a first-class water cooling system (A garden hose with a Skilsaw will not work, as you will have the additional risk of electrocution).
If you do use a dry saw you're going to need a respirator (you don't want to be inhaling that silica dust).