HQI

HQI, often styled HQI, refers to a family of high-intensity discharge lamps used for stage, film, architectural, and outdoor lighting. In typical practice, these lamps are metal halide discharge lamps with a quartz envelope and a fill containing metal halides and mercury. They emit bright, directional light and require a ballast and starting gear to regulate current and ignition.

Construction and operation: The arc tube sits inside a quartz outer envelope. When powered, an electrical discharge excites the metal halides, producing high–intensity light with good color rendering. Variants are offered in several power ratings and base types, commonly 150–1000 watts, with color temperatures from about 3000K to 6000K. Luminous efficacy generally ranges from roughly 60 to 100 lumens per watt, depending on wattage and formulation. Lifetimes are often tens of thousands of hours but the light output gradually declines over time.

Practical considerations: HQI lamps require a suitable electronic or magnetic ballast and a reliable igniter. They can emit UV radiation if damaged or unshielded, so fixtures use protective covers. Mercury content makes disposal a hazardous-waste issue in many jurisdictions. Because color and intensity decay over time, lamp replacement is common in lighting maintenance routines.

Applications and current status: HQI lamps have been widely used for theatre and film lighting, sports arenas, and architectural floodlighting, where intense, controllable light is needed. With the rise of LED-based solutions, HQI lamps are increasingly phased out in new installations, though they remain in use in many existing fixtures and in contexts where color matching and familiar performance are important.