The furnace man

Of course by the time he arrived the furnace was working again and we were back at our normal 69 degrees. Why does it always happen that way? He seemed to look at me skeptically as I tried to tell him how freezing it had been in the house just a couple hours earlier and how we had tried everything we could but couldn't get the furnace started. I told him how my husband had even checked for ice outside in the "vent." I've never been around the side of the house to see this mysterious "vent" but apparently I said the right thing because he nodded in approval and finally seemed to believe we had had no heat. He said since it was working again he could just leave and not charge me a service call. We are going out of town so I thought I'd better have him take a look so we don't come home to broken pipes. He was really quite helpful and even though he didn't find anything wrong he kept giving me tips on how to check the furnace myself so I wouldn't have to call him: "You just pop this panel off and check this pipe here. Just undo this little screw and slide the valve off and take a look inside. If you see any crud just find a little piece of hose like this and attach it to this opening here." I looked around ashamed at the obvious lack of random pieces of hose in our basement. "Uh, we keep our hose out back." He nodded approvingly and again I knew I had said the right thing. "Now just hold your finger over this opening so the pressure pushes the air this way and not up into the air conditioning. You don't want that." I shook my head, of course not. "Now just blow a few times like this and you'll clear the line right out." I watched intently as he blew into the little piece of hose and two or three drops of liquid came out of the opening in the line. "See all that crud that was in there?" No. I nodded my head and wrinkled my nose at the disgusting droplets of moisture in our line. "Here's another thing you can check if the furnace isn't kicking on...just restart the power switch and undo this white pipe here to let some oxygen in because fire needs oxygen to burn." fire? burn? "But don't ever undo this other white pipe because it carries the dangerous gases." dangerous gases? I thought back to yesterday's lunch of bean burritos. "If the furnace makes a sound like this--vruumb, vruuumb, vruuumb, then it probably means there are some leaves clogged in the air inlet outside so just clear those out and it should start right up." I wanted to ask if the "air inlet" was the same thing as the mysterious "vent" but I simply nodded. "You can also just stick a vacuum cleaner in from this side, watch out for these wires, and loosen this black valve." nod nod. "You might have to undo one or two screws so don't forget to put those back in when you are done." nod nod. "Now be careful if you decide to pull out the main regulator because those things can be a pain to put back in and it will cost you a bundle to replace it if it gets bent." nod nod. "You can also disassemble the entire furnace, lay all the pieces out on the floor and then lose 2-3 of the pieces before you put it back together so your furnace will never work again." nod nod. "So be sure to try those quick checks before giving us a call again. " nod nod.