At Mountain View Fire and Rescue, the volunteers keep vanishing.

Tim Perciful, the public information officer, said the department has paid firefighters but also relies on volunteers.

"We are not at a crisis level, but it is needed," said Perciful. "Probably in the last ten years, we have gone from 100 volunteer firefighters to about 40 volunteer firefighters."

What's happening at Mountain View Fire and Rescue is happening across the country.

"It's been a cultural shift, so volunteer firefighters are really needed right now," said Perciful.

Seven out of every ten firefighters in the country is a volunteer, according to the National Fire Protection Agency. As volunteers are aging out, the next generation is not lining up.

"A lot of our volunteers have families at home and full-time jobs," said Perciful, who added that volunteering does require time and training.

Bethanny Grove, a new mom, finds a way to work as a volunteer.

"I went through the volunteer academy in the fall of 2016," said Grove. "I was astounded by how many people put the time and effort in, and it is so rewarding."

The time donated by volunteer firefighters saves localities across the country nearly $140 billion a year, according to the National Fire Protection Agency.

Incentives to become a volunteer firefighter will differ depending on the department. At Mountain View Fire and Rescue, they have a resident program where volunteers can live at the fire station rent-free as long as they work a certain number of shifts.