Buyer beware!! Vredevoogd is unethical. . Vredevoogd "tune up" special became obvious that they are just out pushing new furnaces. The technician was polite and professional but pointed out a hairline fracture in my heat exchanger and said that he will need to shut off my furnace quoting some AGA BS. He said I would need to replace the heat exchanger or get a new furnace before turning it back on and how ironic, they don't make my heat exchanger anymore. Well, this Vredevoogd technician did not realize he was dealing with a degree'd mechanical engineer and probably know how the furnace works as well as he did (maybe more). A furnace heat exchanger is not an air tight chamber to begin with so a hair line fracture should not cause any issue with it's function. Google it, a cracked heat exchanger it is a myth/scam. It only becomes an issue if it is affecting the burners and there is insufficient combustion which is caused by a large cracks or holes in the heat exchanger. The Vredevoogd technician tried to scare me with carbon monoxide poisoning, however I have carbon monoxide detectors in the house that DO NOT indicate any issue. . So if you want to get scared into buying a new furnace with words like "Poisoning" and turning off the gas to your current furnace (when it's snowing outside), then by all means hire Vredevoogd. They will be glad to to give your furnace a tune up (shut off) and try to sell you a new furnace. They must be trying to pay for those TV commercials. Always question someone who says you "need" a new furnace while they are selling you a new furnace. . UPDATE: The below response is not their own words, I have done my research. http://www.shavitz.com/blog/the-dangers-associated-with-a-cracked-heat-exchanger/ Another company trying to sell furnaces.