Hazardous area lighting has developed over centuries, from the first miners’ safety lamps in the early 1800s, to incandescent electric lighting in the 1900s. In the 2000s, new technologies like LEDs have allowed hazardous area lighting to progress even further.

We now have certification systems in place to ensure that hazardous area lighting is suitable for use in the presence of flammable materials and combustible gases, along with ingress protection ratings (IP ratings) for luminaires installed in harsh and industrial settings.

Two common types of hazardous area lighting are ‘well glass’ lighting and ‘high bay’ lighting. In this article we’ll look at these types of harsh and hazardous lighting, their maintenance and their uses for on-scene illumination.


What is hazardous area lighting?

Hazardous area lighting is designed to offer improved safety characteristics in potentially dangerous locations, often in the presence of flammable materials, combustible gases or airborne dusts that could trigger an explosion if ignited.

Lighting has historically posed a high risk of fire or explosion, due to the high temperature of an incandescent light bulb filament during use; however, LED lighting has changed all that, with luminaires that run at a much lower temperature even during constant use.

Well glass and high bay lighting are two of the common types of hazardous lighting seen in industrial settings.


Well glass lighting

Well glass, well-glass or wellglass lighting (all three spellings are commonly used) traditionally features an LED or incandescent bulb placed inside a protective glass dome, which is usually inverted for the light to be used at high level.

The glass dome may in turn be protected by an outer metal or wire cage, especially in exposed outdoor locations like oil rigs and marine installations. Well glass lights have many other names, including ‘harbour sconce’ and ‘wharf sconce’ due to their marine applications.


High bay lighting

High bay lighting is hazardous area lighting designed for use at high level, and can include well glass lights. However, this is a broader term and also covers other shapes and styles of high-level lighting for harsh and industrial environments.

Until quite recently, well glass lighting was typically incandescent, whereas high bay lighting was more likely to use LED luminaires, but the terms are now used quite interchangeably.


How easy is maintenance?

Both well glass lighting and high bay lighting is often installed in hard-to-reach locations, and is designed to require very little maintenance. The protective lampshade and metal cage on well glass and bulkhead lights helps to reduce the risk of accidental damage.

LED lights have again helped with this. Whereas incandescent bulbs can burn out with intensive use, LED lights typically last much longer, offering tens of thousands of hours of operation before the luminaire needs to be replaced.

During servicing, the protective exterior must be carefully removed to allow safe access to the bulb inside. The complexity of this can depend on the certification given to the light fixture:

  • Exe lighting is typically cool-running (e.g. LED lighting) with protection based on preventing exposure to a source of ignition.
  • Exd lighting may run hot (e.g. incandescent lighting) with an enclosure designed using flame paths to contain any ignition.

Both types of hazardous lighting should be serviced by a qualified professional, to ensure that the protective shade and enclosure are reassembled correctly, without reducing the level of protection.


Frequency of maintenance

Regular maintenance can help to keep all hazardous area lighting in good condition. Choosing the right products can make it easier to maintain high bay lighting where access is limited.

For example, the Chalmit Eclipse II LED is suitable for use in Zone 1 hazardous areas. Its corrosion-resistant aluminium alloy construction with borosilicate glass dome includes a side-mounted terminal enclosure, allowing the luminaire to be installed without the need for flame-proof cable glands.

Meanwhile, the Dialight Safesite LED High Bay for Zone 1/2/21/22 is equipped with aluminium swivel brackets, and meets demanding specification criteria while offering reduced maintenance costs and superior quality of light.

In general, annual servicing is a good idea as a bare minimum, in order to inspect hazardous lighting enclosures for signs of damage, but this can vary depending on the product and the presence of specific hazards in the nearby environment.


On-scene illumination

High bay lighting can offer a variety of on-scene illumination. Dialight Safesite LED High Bay for Zone 1/2/21/22 was specifically designed to replace conventional lighting in a wide variety of indoor and outdoor hazardous area applications.

The suspended nature of well glass lighting means that illumination is typically provided over a 360-degree field. Positioning the lamp in different ways can project the light in a specific direction, for example via a pendant, pole or uplighting configuration.

Chalmit Eclipse Jr LED Lowbay is an example of well glass lighting for low bay use, with a unique LED optic for uplighting use. Like its sibling the Chalmit Eclipse Jr Wellglass, it features a prismatic dome, helping to reduce glare and offer consistent illumination.



Well glass lighting and high bay lighting have been developed over centuries of invention and innovation, using performance materials and clever construction to help reduce the risk of fires and explosions.

Trusted brand-name manufacturers and internationally recognised certification schemes mean you can have more confidence than ever in the safety of hazardous area lighting – with only a minimum of annual maintenance needed to keep everything in order.