The tent would need to be double layered and well sealed. You would also need to be very isolated, like no where near residential areas. The sign needs to make it clear that it is unsafe due to toxic gases (ideally placed inside something water resistant so the sign does not deteriorate). You'll also want lab eye wear to stop you going blind. Also, it will smell terrible until it reaches a high enough concentration to overwhelm the olfactory senses. It will not be as peaceful as inert gas, but still very effective. Do research, look in to it carefully, and protect people the best you can.