Furnace wont heat apartment, why?

I rent and had the maintenance guy out here before cuz it was blowing cold air for a long time when I turned it on in the morning. He said that was normal. I timed it tonight and its been on for over an hour and it hasnt risen one degree in here, the air feels luke warm, if that. It started at 68, and its 48 degrees outside. It is warm most the time, seems to be intermittent. Now its nighttime and its going to get to colder, around 40. Should I call emergency maintenance? This cant be normal.