Follow these precautions when using portable light strings:
Inspect the wiring and fixtures before stringing the lights or before they are energized or plugged in. Make sure the outer insulation is not damaged, the plug ends are intact, and the fixtures are not cracked.
The light-string must be grounded. Make certain the plug has a ground prong. Never cut one off. The quality of the ground must be tested frequently. A good ground could save your life if an electrical fault develops, especially when working in wet conditions or on metal structures. If a Ground Fault Interrupter (GFI) is available, use it. GFIs should always be used under wet conditions.
Never string lights so they are near any combustible items. You know from experience, that bulbs get hot. Even if they are not in direct contact with the combustible, heat can build up slowly until the ignition temperature is reached.
All fixtures must have an unbroken bulb installed. The bulb will help prevent you from coming in contact with the exposed electrical conductors that are present when a bulb is missing or broken. When you change a broken bulb, disconnect the power from the light-string and wear gloves to guard against cuts.
Never use an ordinary light string in an area that could contain flammable vapors. When used within an enclosed or confined space, the space must be certified as “Safe for Hot Work” if a conventional string is used. If the atmosphere is not “Safe for Hot Work”, then “explosion-proof” lights must be used. Keep in mind, when you place any type of lighting in an area where flammable vapors are present, you are introducing a source of ignition. This could endanger your life.
You will want to be especially careful during your inspection to make sure that the cord, all plugs, the fixture and the globe are all in place. Don’t forget the gasket at the bottom of the globe. Make sure everything is clean and tight.