The first person to enter the lab in the morning, has to complete a check of all equipment that makes the lab operational. There is a checklist and you go through all floors of the facility and document the status of every piece of equipment and levels on every pressure gauge. Then you do a visual inspection by walking around the lab in what's called the buffer corridor.
While in the buffer corridor you can look through windows into the lab to make sure all status lights are green etc. Once you've documented that everything on the list is as it should be, then you sign it and enter it into a binder in what is basically the antechamber of the facility.
After that you can enter the lab, which has its own set of protocols. If you're not the first one in that day, you check the binder to make sure the checklist was done and the lab is operating normally. Then you need to go through the buffer corridor and look through the windows to see if anyone who is already in there needs anything. There are dry erase boards leaning against the buffer corridor walls by each window, as well as inside the lab, so you can communicate that way. If someone needs something, it's not too late for you to go get it and bring it in with you.
The next step is to get generic coveralls, socks, and a bath towel from a shelf in the buffer corridor. You take those into a locker room. Each door you enter has special security measures. Once in the locker room, you flip a switch that turns a light on on the outside of the room, so anyone in the buffer corridor can see the light and know that someone is in there. The light also indicates if you're male or female so that no one of the opposite sex comes in uninvited.
In the locker room you get naked, put your clothes in your locker, and then put on the coveralls and socks. Then you grab your shower supplies from your locker and head into the personal shower. Entry into, and exit from, the BSL4 suit-change room is only through the personal shower, which also has special security measures. So you enter the shower, set your shower supplies down and then exit the shower (without showering) into the suit-change room - the place where you don the BSL4 suit. Sometimes there are a few people in the suit-change room. Coordinating entrance with others can save time for everyone.
So, in the suit-change room you put on a hair cap and nitrile gloves. Then you get your suit off the hanger and examine the seams and valves and look for obvious holes, tears or any signs of compromised integrity. Every so often you are required to also test the suit by sealing the exhaust valves, connecting to an air hose and filling with air. Then you spray the suit with a soap mixture that will form bubbles if there is any air leak. This test, while important, can't be done every time you wear the suit because being filled with air stresses the seams. So it's a balance.
Once the suit is ready to go, you put earplugs in, connect the air hose and put it on. Entrance to, and exit from, the actual BSL4 lab is through a chemical shower, so you disconnect the air hose and access the chemical shower. You are not showered on the way in, you just move to the other side of the shower and move through the door into the lab. Each of these doors takes some time to open due to pressure differences between the rooms.
By the time you get into the BSL4 lab, you usually don't waste too much time getting connected to an air hose. Once in, you do what you went there to do. When you leave, you do the whole process in reverse and at each shower you actually shower. The chemical shower is several minutes of a detergent/disinfectant shower, so you connect to an air hose for the duration.
While showering you use large scrub brushes to scrub your suit. You also have to dip your gloved hands and booted feet into a large container of the same disinfectant. Then the shower switches to a water rinse and you do your best to rinse all the disinfectant off of the suit. Once done, you disconnect the air hose and exit the shower. No one can enter or exit the lab while the shower is running, so scheduling is critical.
After the shower you remove the suit and dry it off, then you remove your nitrile gloves and hair cap and put them in the trash. Then you move to a private area outside the personal shower and remove the coveralls and socks and they go into a designated bag to be autoclaved later. Then you walk naked into the personal shower, where you are required to use soap on everything and shampoo your hair. Before leaving the personal shower you have to clean it with disinfectant and a mop/squeegee to help dry the floor so the next person walking through isn't grossed out. Then you exit into the locker room to dry and get dressed so you can exit.