Arc-Fault Circuit-Interrupters are relatively new electrical safety devices that first appeared in the 1999 National Electric Code. AFCI devices look very similar to GFCI devices, in that they have a test button and a reset method, and they come in the form of circuit breakers, receptacles, or stand-alone devices. The big difference between the two is that GFCI devices are designed to prevent people from getting electrocuted, while AFCI devices are designed to prevent fires. For an excellent in-depth discussion of AFCIs, check out Douglas Hansen's article, AFCIs Come of Age.
The 1999 National Electric Code required AFCI protection for branch circuits containing bedroom receptacle outlets, with the requirement taking effect on January 1st of 2002. Since then, AFCI requirements have been expanded many times, to the point where AFCI protection is now needed for "all 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices installed in dwelling unit kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, and similar rooms." The NEC defines an "outlet" as "A point on the wiring system at which current is taken to supply utilization equipment." In my words, the NEC definition of an outlet is a place where power is provided to do work.
Side note: If you read my inspection reports, blogs, or anything else that I write, when I say "outlet" I mean the same thing that the rest of Minnesota calls an outlet; that thing in the wall that we plug cords into.
The 2011 NEC also had a section that took effect on January 1, 2014, requiring AFCI protection for any new or replacement outlets. I blogged about that topic right after this requirement went into effect. Click this link for details on that topic: New Electrical Safety Requirement: AFCI Protection for Replacement Outlets
To put it simply, AFCI protection is needed all over the place in new homes, it's needed any time new outlets are installed, and I expect the requirements for AFCI devices to keep expanding until everything is AFCI protected. That's certainly the direction things are headed.
So back to the title of this post...
Most home inspectors already recommend adding GFCI protection for the areas where people are most likely to get electrocuted, so shouldn't we also start recommending AFCI protection for the majority of the 120-volt branch circuits within a home?
I say no.
Safety is important, but safety benefits need to outweigh the costs to justify upgrades. I have no problem telling my clients to add GFCI protection because it's an easy call to make. GFCI devices add a lot of life safety for a small price; usually $10 - $15 for a GFCI outlet, plus a little bit of work that I consider to be a good "starter" electrical project.
On the other hand, I would never recommend installing a sprinkler system in an existing home, because I believe the cost of the sprinkler system would outweigh the added level of fire safety.
I feel the same way about AFCIs; they don't offer enough added safety to justify the cost. Adding AFCI protection for an entire branch circuit typically requires the installation of a AFCI circuit breaker. These circuit breakers cost about $30 - $50 each, and installing them means replacing existing circuit breakers, which I don't consider to be a good "starter" electrical project. Additionally, many older electrical panels will not accommodate AFCI circuit breakers, and multiwire circuits present additional challenges.
What about older generation AFCIs?
As mentioned in Douglas Hansen's article referenced above, the first generation of AFCI devices really weren't all that useful. They weren't exactly defective, but they also didn't do a great job of preventing fires because they were only capable of detecting parallel arcs, which are uncommon. These older AFCI devices could be found in homes built between 2002 and 2008. Newer generations of AFCI devices, called "combination" AFCIs, are far more effective at preventing fires.
There are plenty of home inspectors who tell their clients to replace the old generation of AFCI devices with new combination AFCI devices, but I don't. I think it's inconsistent to recommend replacing old AFCI devices with new ones if I'm not also recommending AFCI protection be added throughout pre-2002 built homes.