Tritium, also known as 3H or H-3, is a form of hydrogen. The signs pose little or no threat to public health and safety or security. They serve an important safety function by marking exits to be used during power outages and emergencies. These signs do not require electricity or batteries and can be used where it is hard to install electric signs, such as above doors. EXIT signs that glow in the dark often contain a radioactive gas called tritium.
