Imagine your lungs 8x the size they are now..that's how large a giraffe's lungs are!!!
Why is this? Well the giraffe needs to bring oxygen to much larger muscles than us! The air travels down the trachea into the lungs and is then delivered to the rest of their body. The trachea is very large and narrow which leaves an area of "dead space" where "old air" remains in the giraffe. To help with this giraffes breathe at 1/3 of the rate that we do. They still breathe in oxygen and expell carbon dioxide just like humans.