I think sometimes the error is too far on the side of safety......that is here is one case in which a smoke alarm supposedly caused a fire......the question that is not answered is were the other smoke alarms operating and sounding at this time??..........also if the AFCI was there and had tripped to the off position, would that be enough to stop this fire OR was it caused by an over heated component that had already charred the circuit board which was already at a combustible temperature had caught fire and then the arcing of the 120v. feed would have tripped the AFCI? (the most likely scenario).........From your support article it seems like there was a BIG jumping to a conclusion to get support for this recent code addition.........

Another point......many wired in smoke detectors DO NOT have the battery backup mentioned in previous responses.......so if a general lighting circuit in a residential home was used as the power source for the smoke detectors and the AFCI tripped........where is the protection??...........as the fire may have already started (see the example later on).......

Since now in the fire alarm industry, fire alarm cables have a red jacket to distinguish them from other cables..........let's have a red jacketed 14/2 cable to supply ALL the smoke detectors using 2 circuits minimum in the residence and this red jacked 14/2 be fed from a standard 15 amp breaker that also has a red color or marking and be secured in the on position, also the mounting boxes for smoke detectors be made from red plastic or be colored red to identify them and the circuitry they contain.........or require that all the smoke detectors be on several (minimum 4) circuits in the residence to prevent one AFCI from removing power from the smoke detectors when it trips.......

I understand the logic behind the addition to the NFPA code for the AFCI breakers..........but let us not undo the good that has become established in a residential home with the addition of smoke detectors by having them non-functioning because of our zeliousness to provide the safest envirement possible to live in...........

Remember we can not prevent all hazards by legislation.......There is a personal level of responsibility there too..........IE, placing an electric heater too close to a bed or couch will start a fire.......when a lamp cord finally arcs and trips the AFCI shutting down the heater.......The fire is started and the AFCI did not prevent it!!.........and that AFCI may have shut down the smoke detectors closest to the fire, removing the early detection that the smoke detectors are to give the people dwelling in the residence.........i agree with their use but lets not go crazy or we will have frivolous law suits similar to holding a hot cup of coffee between you legs and getting paid for burning your thighs because the hot coffee splashed on your legs while driving your car.........

Lets work to keep smoke detectors operating...........I personally do not like AFCI breakers ahead of smoke detectors for the above reasons!!.........