With respect to the janitor or custodial position that is offered to you, you may have to clean places amidst the public during the business operation times. Your answer should be that you are comfortable working in such environment where customers are around. You can say that you started your career by working in customer service and hence you’re used to working in places where public and customers are around.

You would find it to be interesting as you get a chance to interact with other people. You can also mention that you always concentrate on the job and the task you handle; you would not be interrupted by people around.