The show stresses the importance of working together and setting differences aside when other people's lives are on the line. There's also a sense of connectedness between the firehouse and the surrounding community.
The main characters work in a dangerous field where injury and even death are common, but the show doesn't overemphasize violence. Some characters pull weapons, get in fist fights, etc. Blood is visible but not excessive.
Some sexual innuendo and light banter, with some kissing and bare skin from the shoulders up. A man and women who work together are sexually involved.
Unbleeped language includes "bulls--t," but words that strong are rare.
Some characters smoke cigarettes and drink socially. One character uses injectable prescription drugs.