Mysa In-Floor contains a 5 mA Class A GFCI.
GFCI stands for Ground Fault Circuit Interrupter. It is a safety device that interrupts power to your floor heating system in the event of a power surge or other power related issue. GFCI's are likely already in your home, most power outlets in North America are required to have them as a safety measure. Class A means that if a fault is detected the GFCI can shut off power to the device with only 5 mA of leakage.