Arc Fault Circuit Interrupters (AFCI)


What is an arc fault circuit interrupter (AFCI)?


Technology advances provide us with many new conveniences for our modern lives. It also provides us with new devices to keep us safe in our homes. One such device is the Arc Fault Circuit Interrupter or AFCI.

In my last blog, I spoke of GFCI protection in our homes. AFCI protection is similar, but it protects us from a different danger. The AFCI purpose is to sense an arc in an electrical circuit.


What is an arc?

An arc occurs when a current is passed (through air) across a gap, using the air itself like a wire. For fire safety, the wires in our homes have insulation to help reduce high heat situations. Air is not insulated! The picture below shows an arc between a hot wire (black) and neutral wire (white). It happened because the insulation on each wire has broken open.



Courtesy of


Hold on, are all arcs dangerous?

The answer is no! Think of the spark plugs in your car; a spark plugs purpose is actually to create arc situations. These are safe, because the duration of the arc is pretty short. A home circuit arc situation is dangerous because the duration of the arc can be much longer. Since arcs produce extreme high heat, this can result in major fire hazards inside your home.


Electrical fires in homes are common!

A 2007 Canadian fire statistics report, states that 10% of all fires in homes are electrical in origin. Also, this report says that a total of 42,753 fires resulted in the following. 224 civilian deaths, two firefighter deaths, and $1,551,657,179 in direct property damage! These statistics are from a report by ccfmfc. So, current building codes are mandating more safety devices for our homes.



Arcs happen in the home?

Arcs occur in our homes in many ways. Most arcs found are from loose connections at terminals/outlets. But they can also occur, if a person were to drive a nail through a wall into a wire. Also by vermin chewing on wire up in the attic or behind a wall. So, the AFCI senses these arc situations and attempts to cut power to the circuit to reduce fire hazards.

Specifically how does an AFCI protect the home?

An AFCI works by sensing the signature of an electrical arc. This means the sequence of current spikes and the voltage drops. Current sequences should be fluid and similar in spike and drop. If the sequence is erratic it can indicate the possibility of an arc situation (see Picture 3 below).

Diagram-explaining-arc-faults-in electrical-circuit

Courtesy of

When this happens the breaker will cut the power to the circuit. The location of AFCI devices are a special circuit breaker the main electrical panel. The breakers have a special coloured test-button near its handle (see Picture below).

Note: GFCI breakers also have special coloured test button. A magnifying glass is often required to read the label on the breakers to identify them.



Where in my home is it needed?

Building codes introduced AFCI protection in 2002 for wiring that supplies bedrooms. In 2008 many building codes expanded the areas to that needed protection to most rooms of the home.

Not needed?

Areas that don’t need AFCI protection, because they are already GFCI protected. Include the garage, bathrooms, kitchen, and laundry rooms.

Bottom line

Building codes for our homes are not retroactive. So many of our homes aren’t required to have AFCI protection. Many clients ask me “my home hasn’t had these problems so far, this seems like an expensive add-on”. Yet, my answer is this: How safe do you want your home to be? Are you willing to spend some money to help ensure a safe living environment for your family?


Author: Geoff Bohaker at Shelter West Home Inspections


About Geoff Bohaker

Geoff is the owner and operator of Shelter West Home Inspections in Vancouver, B.C., Canada. His boundless curiosity for buildings and how they interact as complete systems, guide him on his journey to educate his clients on making the most informed home decisions possible.