One of the concerns Kevin hears a lot is, “I’m afraid of my oxygen-acetylene welder” because of the “pops” and the open flame. He begins at the beginning by opening the oxygen and acetylene bottles a quarter turn. He says some people like to open them all the way because they think that doing so better seals the valve, but the Praxair salesman where Kevin gets his bottles and gas says the newer valves don’t leak like that anymore. So Kevin says he opens them a quarter turn, but you should do whatever you are comfortable with. Next he recommends setting the regulators according the manufacturer’s specifications for the welding tip you are using. Kevin also recommends that, for safety, you take advantage of the units’ long hoses – 15, 20, sometimes as much as 50 feet – and put the bottles away from where you are working. Then, if you do have a leak, the bottles are out of the way. Also check all connections with a squeeze bottle of soapy water. Use it to test your bottles, your connections, and check the hose for cracks, too. To light the torch, be aware that the red hose is acetylene and the green is oxygen – just like its bottle. First, Kevin opens the acetylene valve on the torch handle about 1/8 of a turn. Then he uses a striker to light the acetylene gas coming out of the welding torch tip. Next he open the oxygen, and the flame starts to change. As you open the oxygen, the flame gets larger. Kevin first shows how the flame looks when it is not adjusted correctly, then opens up the oxygen a little more. It creates a sharp cone of blue flame inside the larger flame, which is the neutral flame you want. Then you’re ready to start bending, cutting or welding. Kevin adds that you don’t need to adjust the flame after that, unless you bump the knobs. Running out of gas shouldn’t affect the flame because the pressure regulator controls it. When you have almost no oxygen or acetylene in the bottle, it just won’t work anymore. To turn off the torch, if you turn off the acetylene first, then the oxygen, the oxygen-acetylene welder shuts itself off, although sometimes it will pop as it shuts off. Kevin says that’s not dangerous, but it is a little scary at first. He lights the flame again and turns off the oxygen first, then the acetylene, which is the correct way (it turns off the welding gas in the same order you turned it on). Then you shut off your bottles. Kevin says that some people like to bleed the pressure out of the hose lines once the bottles are off, but he just considers that a waste of welding gas. Overall, Kevin says, oxygen-acetylene units aren’t scary, but you do have to respect them.