SureFire Mechanical is a professional and top-notch company. I've had trouble finding someone to handle my furnace maintenance: had a few instances of people just not being professionals, leaving me hanging when we had a scheduled appointment, not really doing a thorough job, or leaving me with a furnace that was "sort of" functional. SureFire Mechanical's personnel, on the other hand, are extremely professional. They are easy to make an appointment with (they respond to email or phone), do a thorough job, are willing to explain exactly what they are doing and why, and the owner - Jason - solved problems that in fairness, were not really his issues, but he felt compelled to take them on in order to do a thorough job and leave things in a state that he was comfortable.
With an old furnace - mine is 20 years old - there are so many things that can be serious hazards. Just because these units exist in every house doesn't mean that they are adjusted correctly, serve the owner efficiently, and that they don't introduce risk. I had every sense that Jason takes his company's work very seriously, maintains his own standard for safety and quality, and will stick with a job until it's finished to his satisfaction, including dealing with all the little unpleasant surprises that can come up in dealing with old equipment. ...Oh, and btw, he does this in a good-natured manner, with the wisdom of someone who has been handling these types of jobs for a while, doesn't surprise easily, and doesn't nickel and dime you in doing the work. Anybody would do well to hire these guys.