We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is a Mercury Vapor Lamp?

By Robert Robillard
Updated May 17, 2024
Our promise to you
About Mechanics is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At About Mechanics, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

A mercury vapor lamp is a type of high intensity discharge (HID) lamp that is predominantly used for commercial and outdoor lighting. It was the first metal vapor style of light fixture to be mass produced for general lighting. The mercury vapor lamp produces a bluish white light by introducing an electric current to mercury vapor within a sealed glass tube. The bulb is comprised of an inner tube, called the arc tube, and an outer tube.

The arc tube typically is made of quartz and has an electrode at each end. Inside the arc tube is a small amount of mercury and a buffer gas, usually argon. The buffer gas helps to carry the discharge while the lamp warms up, which can take up to 10 minutes. It also produces the heat required to vaporize the mercury.

The outer tube of a mercury vapor lamp is generally filled with nitrogen, or a mixture of nitrogen and argon. Its job is to provide thermal insulation and protect users from the ultraviolet (UV) radiation that is common with mercury lighting. This protective shell can be made of clear, borosilicate glass, but it is often coated with a phosphorous finish to correct color and add further UV protection.

As with fluorescent lights, mercury vapor lamps require a ballast to supply the proper voltage and regulate the current to the electrodes. The ballast is designed to be used with a specific size, or wattage, of bulb. Using a mercury vapor lamp with a ballast that was made for a higher wattage bulb might damage it or cause it to explode. Using too small of a ballast will result in lower light output and can shorten the life of the bulb.

When used with the correct ballast and properly maintained, a mercury vapor lamp has a long service life. The average life expectancy is more than 24,000 hours, or nearly three years of continuous use. Unless they are damaged, these lamps typically do not burn out completely. Over time, deposits build on the inside of the arc tube wall, causing a phenomenon called lumen depreciation. As a general rule, lumen depreciation will cause a mercury vapor lamp to produce 50 percent less light every five years.

As more efficient types of HID lighting fixtures have entered the market, mercury lamps have become less popular. Although the bulbs are still widely available, the United States banned the sale of mercury vapor lamp ballasts in 2008. According to the ban, existing fixtures can remain in service but, as they burn out, they must be replaced with newer, more efficient lighting alternatives. Similar laws have been passed in the European Union, which set 2015 as the year when mercury lamps will no longer be approved for lighting purposes.

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.

About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.