You put all the people who come to help you or who just happen upon you at serious risk. The method is appealing because it’s easy to mix the household material, and death comes fast and reliably.
Even if, like a student at Rensselaer Polytechnic this morning, you leave notes in your dorm room warning people off, exposure to others may well happen.
Six people were treated at a hospital; a hazmat unit spent hours cleaning up the building.