As part of my routine home inspection of gas powered heating systems and appliances I like to first look over the fuel storage (LPG) or fuel source (natural gas) and supply lines all the way to the device's regulator, both visually and with a gas detector. Over the years I've seen it all, from small leaks in a threaded connection to larger leaks at the regulator.
NO GAS LEAK IS ACCEPTABLE
One leak I found was in a gas regulator. The house had not been occupied for some time and had been winterized with the heat turned off. This leak was too small to cause an odor in the basement but when the burner door was opened the odor was strong. Had I or anyone else turned on the heat there may have been an explosion.
When installed and maintained properly these systems are safe, reliable and efficient. But when something goes wrong it can be catastrophic. Before using a gas appliance of any kind for the first time you should read the manual and have it inspected. You should also have it serviced annually including the fuel source and supply lines. I'll end with this sobering note. In some years, nearly 10% of the gas system I've inspected had gas leaks