High concentrations of halon can create an oxygen-deficient environment. This can cause people to suffocate.
Placing skin in contact with the liquid being sprayed from the extinguisher can cause chilled skin and frostbite.
Skin and Eye Irritation
Like most toxins, halon fire extinguishers can cause damage to eyes and skin. Irritation can occur even without direct contact with the halon.
Interruption of the Central Nervous System
Large amounts of halon gas that get inhaled can interfere with the proper function of the central nervous system. The symptoms of this are dizziness and a tingling sensation in the extremities, and in some cases victims will also go unconscious.
Halon gas can cause irregular heartbeats and an increased heart rate in response to adrenaline. In extreme cases, this can result in a heart attack.
A punctured or damaged halon extinguisher can present a danger because the release of pressure can turn the metal cylinder into a high-velocity missile.