Physical Plant needs to enter your lab to initiate repairs. What should you do before the worker enters your lab? Allow them to enter. They are familiar with engineering issues already. It should be fine. Make sure the worker is aware of the locations or surfaces that they should not come in contact with while in the laboratory. Remove all hazardous materials from the area in which they will be working. Allow the worker to enter the laboratory. While continuing your experiment try to keep an eye out for the worker so he/she does not come in contact with hazardous material. Have the worker return when you are cleaning up from your work day or have put everything away. Allow the worker to enter. After he/she has located the problem, leave the lab so they may complete their work.