There is a wide variety of flexible gas lines on the market today. Most of the companies that sell them require the user to be certified before installing these products. The gas line itself is normally good quality , the problem is that all of the manufactures have different guidelines when it comes to attaching the terminations (fittings) and this is where most failures occur. If you are experiencing gas odors, you need to have a plumber or HVAC tech who is TRAINED in installing these products correct the improperly installed fittings.