However, this effectiveness comes with a "double-edged sword" caveat. The very chemical aggression that makes the acid useful makes it incredibly dangerous. The risks of using plumbers' acid fall into three main categories: personal safety, pipe integrity, and environmental impact. On a personal safety level, the acid is hazardous. It can cause severe chemical burns upon contact with skin, and if splashed into the eyes, it can lead to permanent blindness. Furthermore, when acid reacts with organic matter, it often creates heat and toxic fumes. In unventilated spaces, these fumes can be harmful to respiratory health. There is also a specific danger regarding mixing chemicals; if a homeowner has previously used a different drain cleaner (particularly one containing bleach or ammonia), introducing acid can create a violent, even explosive, reaction or release deadly chlorine gas.