This up-and-coming sandwich chain founded by firemen grew sales by $110 million in one year

Firehouse Subs is stepping in to take market share from Subway.

The quick-service restaurant chain boosted sales by $110 million last year, according to QSR Magazine. Firehouse has nearly 1,000 locations in the US and plans to double its footprint by 2020.

Firehouse also launched its first national TV ad this year.

The brand was founded by brothers and former firefighters Chris and Robin Sorensen in 1994.

Firehouse's menu includes hot and cold subs and salads.

Here's one of its latest specials, a pulled pork that has been smoked for 12 hours.

The idea of "fresh casual" food that hasn't been overly processed is taking off. This trend is hurting Subway, which ruled the sandwich world for years.

Firehouse's subs are huge, leading to customers thinking they're a good value.

The chain also tries to be family-friendly, offering fire hats for kids to wear.

Firehouse also offers catering.

The brand was named best choice for customer atmosphere in research firm Technomic's 2015 consumer survey.

It's the second fastest-growing franchise in America, according to Nation's Restaurant News.