Our furnace is from the 1980's, has not been serviced or kept up very well. A few days ago there was a gas leak from the unit on a main pipe inside the furnace itself. The gas company said the Unit and pipe needed replaced and possibly the entire furnace needed replaced and shut the gas off at the main valve on the furnace and red tagged it. Our landlord was extremely mad that we called the gas company, told us they had shut the line down over a year ago with the previous tenant and didn't tell him they had tagged it, and then he told us he tightened the unit and that it's fine and DO NOT call the gas company again if we smell gas, call him. I'm concerned that since the gas company said it needed replaced and he isn't replacing it that it could leak again at any time. Are we in danger?

Anytime there is a gas leak you are in danger. However,what needs to be done is the responsibility of the landlord. I would however, document your concern in writing, to the landlord.