Building codes are great, they provide a standard for everyone to follow. What is the result? Buildings that are all built the same? Not so much. Realistically, people do whatever they want, additions here, and alterations there. Many buildings predate modern codes, others have changed occupancy multiple times in their history. You have no idea what is hiding in a building’s walls. The only way for you to know is to open them up. Start with a bit of caution, when you see what’s behind the finish then you can go to town on it, but always remember there could be anything, anywhere.
There could be high voltage wires running behind the finish wall, don’t bet your life that you’re safe with a fiberglass rake. There could be four layers of 5/8” drywall with an elevator shaft on the other side. There could be a light shaft that was walled off long ago but is now providing the fire with an unchecked path out to the roof, or it could be a concrete block wall. If it’s your job to open up, just keep in mind what kind of history the building could have had.
You already know, but if your area has a few buildings going up, or being rehabbed check it out. See the type of work they do, you are going to visit the building for an emergency when the work is done, bet on that. So have an idea what’s going into or being taken out of the building. Who knows, with a bit a smooth talk you might get to help with the demo… your way.