What is an Arc Fault Circuit Interrupter? I often get this question at newer homes when we take a look at the circuit breakers in the service panel (fuse box). AFCI protection is a newer requirement of the National Electrical Code. Initial implementation for some new construction occurred in 1999. The 2017 NEC requires AFCI protection in almost all branch circuits in new construction and when replacing older receptacles/outlets during remodeling.

Most people are familiar with a GFCI protected circuit. GFCI outlets protect people from shock hazards. AFCI protected circuits protect the whole branch circuit from conditions that could result in a fire. The outlets in protected branch circuits look the same, the protection comes from the AFCI breaker in the service panel/fuse box. 

As the NEC continues to evolve, more rooms and branch circuits will be required to have AFCI protection. As of 1 SEP 2017, Washington State adopted the 2017 version of the NEC. Almost all circuits in a newly constructed house will be required to have AFCI protection. If you are remodeling a room or even changing a receptacle, the NEC requires that branch circuit to be upgraded to AFCI protection at the service panel. AFCI breakers need a specific type of installation, it's not as simple as swapping out an older style non AFCI breaker. AFCI breakers are best installed by an electrician to ensure proper operation and that they are actually protecting the circuit.

Great overview of Ground Fault Circuit Interrupter outlets. 

It looks like the original post was a bit short or possibly the bottom rotted away. To fix the bad post, the previous owner added a short section of newer pressure treated wood and butted the two ends together. At least he/she toenailed it together though they forgot to add more than one nail for the post support bracket.

Though the owner did make the post a bit longer they did so by making the overall structure weaker. This post is not going to do well with a large group of people moving on the deck during a BBQ.

There were actually two posts repaired this way on this particular deck. Both need to be replaced with the correct length of post (using one piece of wood) and correctly fastened to the concrete footing and beam above. 

Look at this video from This Old House. They do a great job of showing the correct way to replace a damaged deck support post.