It can be dangerous if you do something stupid. If you keep a level head and take necessary precautions and protect yourself properly, you'll be fine.
Like I said, there are techniques for keeping yourself safe while astral projecting. Gemstones such as Blue Calcite, Vanadinite, and Amythest help with projecting in general. Hematite, Jasper, and Jet help protect the physical body. Atacamite and Azurite protect the spiritual body.
You can also sage and clease the area before and after the process. To do this, you can get a bundle of sage, light it, and then spread the smoke around the room to cleanse any negative energy. Take some salt and line it at your doors, windows, and closets to add protection.