HID Safety Precautions

HID lamps produce a very bright white light. Manufacturers use various designs of HID lamps. Regardless of the design, they generally require a high-voltage spark of up to 25,000 volts to start and a high operating voltage (e.g., 40–85 volts AC) to maintain light. To generate the voltages required to operate, a transformer and electronic circuitry called a ballast are used to supply electrical components.

Several safety precautions should be taken when working on HID systems. There is a risk of electrocution, burns, or shock from the high voltages generated by the HID system. If diagnosing the HID system, be very careful when working on the system when it is live. You should wear safety glasses, high-voltage safety gloves, and safety boots, and you should ensure that the vehicle, engine compartment, and ground under the vehicle are dry. Do not touch the ballast while it is operating; it will often be generating a lot of heat. Persons with active electronic implants, such as heart pacemakers, should not work on HID headlamps. If changing out the bulb, make sure the headlights are turned off. The manufacturer may specify that the battery be disconnected when replacing the bulb. If so, follow the manufacturer’s instructions.

There is also a risk of injury caused by exposure to ultraviolet light produced by the HID lamp if the lamp is operated outside of its housing. Once ignited, the pressure inside an HID bulb can build up to a very high pressure (around 220 pounds per square inch, 1517 kilopascals) due to the high operating temperature (about 1500°F [816°C]). This pressure creates a potential explosion hazard, so do not attempt to power an HID bulb outside of the headlamp assembly to test it or operate it near flammable gases or liquids. Also, the bulb must be maintained in a horizontal position when it is on; otherwise it may overheat and fail. HID headlamps use various heavy metals in their construction; therefore, it is important to always dispose of the bulbs in an environmentally friendly way. Avoid breaking bulbs, as there is also a risk of poisoning caused by inhalation or skin contact of heavy metal vapors and toxic salts.