Post apocalyptic volcanic eruption book about pair of survivors trying to reach a bomb shelter type of place

This is a survival after a Volcanic eruption. The volcano has erupted and this guy is packing up his shop to start traveling towards a shelter where his friends are waiting. He is almost ready for his trip to start when a police woman shows up - I don’t remember why, but he explain by he is leaving and she decides to go with him. She had a young child, so they all begin to travel together. The ash in the air get to be so thick that the vehicle they are in is starting to stall out bc of the filter getting too thick. Whenever they leave the vehicle they must wear a type of breathing/filtering mask. The guy creates a type of babysit case that allows the baby to breathe through a filtered type of device. They get bogged down in the middle of a city, and then they need to fight off bad guys while trying to rebuild/fix their vehicle. They continue on their way and make it to the town where the shelter is located. While they are waiting in a grocery store for their friends to come pick them up a guy shows up saying that he is with their shelter group people. They keep questioning the guy and everything and it turns out that the lady cop has to shoot him bc he was lying. They end up reaching the friends and the shelter.

Kennedy Layne Endless Flames