Question: Approximately two years ago this fall,my wife and I purchased a Jotul DV45 Spirit direct vent gas insert fireplace from our local dealer in Brandon,Manitoba and it appears he was not very familiar with the installation requirements for the unit as we have had problems since,initially with snow blocking the roof vent, and now have a problem where the fireplace will remain on for only a few seconds and then the flame seems to be lifting off the logs and it shuts off.We have had the dealer and his installers here to look at this and we have been told that they do not have the answer for sure but have contacted the head offive in the USA and have some ideas to try to solve the problem.We have now been waiting for approx. one month for them to follow up with us and we are becoming frustrated.We have only used the fireplace once this past winter and only a couple of times the previous winter(the first winter we had it).I tried to turn it on in June this year on a cool day and this problem presented itself.It is a beautiful black cast iron fireplace and we hope that this can be sorted out so that we can enjoy it this fall/winter. Answer: You are either experiencing a lack of combustion oxygen, or diluted oxygen that is mixed with exhaust gases. First, remove the front glass and turn the unit on. ; Does it operate okay? ; If so, you have a vent problem ;resulting in a combustion air supply problem. If the flames appear to be tall yellow with black tips before turning blue ; lifting off, you have an air restriction in the vent. ; First, check the termination cap for bird's nests, or anything else that may have lodged itself. ; Perhaps a section of metal on the cap was inadvertently bent during installation. ; Then, have each vent section checked for integrity. If the flames are tall, blue, and stringy before lifting off, you have an inadequate air supply meaning that there's a mix of air and exhaust gases.The exhaust gases are recirculating back into the firebox, sort of like water in your car's gasoline tank. ; Have each vent connection resealed with high temperature silicone. If the unit simply shut down after a minute or two, then it would be something else with the valve, TP/TC pilot assembly, or switch. ; But the flames are lifting off, suggesting air supply problems. That's where I would focus my troubleshooting.