They’re devices that help protect against one type of electrical fire hazard called an arc fault. An arc-fault is an unintentional discharge of electricity in a circuit. This can be extremely serious if nothing is done to prevent it.
What causes an arc fault?
Arcfaults may occur anywhere in the home's electrical system as a result of:
Worn electrical insulation or damaged wire
Misapplied or damaged pug-in appliance cords and equipment
Loose electrical connections
Accidentally piercing electrical cable behind drywalls with a drill bit, nail, or screw
Hammering electrical cable staples too tightly into studs during rough wiring
Natural aging and cord exposure to heat vents, sunlight, or foot traffic
When an unwanted arcing condition is detected, an AFCI de-energizes the circuit, and reduces the potential for a fire to occur.
The solution to this problem is an arc fault circuit interrupter, or AFCI.
Arc fault circuit interrupters, or AFCIs, are devices that provide a higher level of protection by detecting hazardous arcing conditions and shutting down the electricity before a fire can start.
There are three types of AFCIs.
Combination AFCIs (combining the features of branch/feeder and outlet AFCIs)
Although the new safety requirements are limited to new home construction, AFCIs can provide increased protection in existing homes as well. Since the probability of electrical fires increases with the age of the home, older homes with aging and deteriorating wiring systems can especially benefit from the added protection offered by these devices.