ER Etiquette

Have you ever had to use the restroom at a public place and you are not sure if the restroom is occupied? What do you do to make sure that it isn't?

While I was at the ER for my most recent visit, I had need for use of the restroom. I knocked on the door and there was no reply. I opened the door half way in case there was someone in there, thinking they could yell out and I would close the door and wait till they were done. All I heard was a machine sound "psst...psst...psst".

The doctor walked by and I closed the bathroom door while I chatted about the next step for Zander's treatment. After our conversation I began the process again. I knocked on the door, no answer. I opened the door half way, "psst...psst...psst." I figured I was safe.

It wasn't until I opened the door fully that I realized that the bathroom was in fact occupied. There sitting on the toilet, looking me directly in the eyes was a Sudanese woman with her long robes that covered all the way to the ground. As our eyes locked I heard the machine sound once again coming directly from her mouth, "psst...psst...psst". I quickly closed the door.

So my question is...what is proper ER etiquette for making sure someone is not in the bathroom before you open the door?