Being galvanized tubing, EMT is coated in zinc which, when burned off, can result in flu-like symptoms if you breathe it in for too long. This condition is known as metal fume fever. Fortunately, having the right safety equipment can prevent this and will allow you to braze the material as much as you need.
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Position the EMT conduit that you are going to braze on a steady work surface you can apply high levels of heat to without a problem. Avoid attempting to braze on a wooden surface or on interior floors of your home. Use a workbench with a bench vise, if possible.
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Clamp the two pieces of conduit together in the manner in which they are to be brazed, and then turn on an electric fan to blow the gas produced by the brazing process away from your face. Open the exterior doors and windows if you are brazing in a workshop.
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Light the brazing torch, and while wearing the gloves, brazing goggles and respirator, heat the pieces of EMT conduit that will be brazed together. You will know they have reached the correct temperature when the metal glows a faint orange-yellow color through the brazing goggles. Hold the flame over the spot where the braze is to be produced, and with your other hand, introduce the brazing rod to the flame.
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Press the brazing rod against the joint where the EMT conduit is to be brazed. After two to three seconds, the brazing rod will begin to melt. Allow the molten metal to flow into the joint, using the brazing torch and the brazing rod to manipulate the flowing metal.
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Turn off the brazing torch when the joint has been brazed shut. The EMT conduit will remain hot for approximately 20 minutes before it can be handled with bare hands. Allow the electric fan to continue blowing cool air over the conduit until it has finished cooling.