You'll start off on a screen with a burning building, 14 stories tall. Move your fireman to the right to enter the building. Each of the 14 levels has a timer, you have approximately 30 seconds to put out as much of the fire as you can and safely exit the room at the top. When the timer gets down to about 5 seconds, the score will start to flash to let you know that time is about to expire. Each level of the building has it's own unique floor plan, some are more challenging to get through than others. You'll score 10 points for each fire that you put out. Once you've made it to the exit, you've cleared that level of the building and can move on to the next. Each time you clear a room, you'll go back to the building screen and you'll see one level of fire disappear. Enter the building again to move on to the next level. The goal of the game is to clear as much fire from each room as you can (racking up as many points as possible) and safely exit the building. You can win the game without putting out all of the flames.
There are three levels of difficulty which are selectable at the title screen. Push up and down on the joystick to select the level, then press fire to start the game. The fire moves progressively more quickly in each level, and in level three you begin with only 3 fireman rather than 6.
I've included some screenshots below. The screenshot of the burning room of course doesn't show all the flames due to the flicker, there's much more onscreen than I can capture in a screenshot. The game is basically complete, although it still lacks audio. I'm going to be working on that next and will post a new version with sounds when it's finished. Comments and suggestions are welcome!
EDIT: Version 24 adds audio to the game and has a few color changes and bug fixes. As of right now, I expect it will be the final version.