Combining a luminaire with both high temperature resistance and explosion protection is technically possible, but requires a careful combination of thermal design, a certified housing, and the correct ATEX classification. Both requirements present conflicting challenges regarding material use, cooling, and electrical components, which means standard solutions almost always fall short. In this article, we answer the most frequently asked questions about high-temperature ATEX lighting and we help you make the right choices.
When is a luminaire both high-temperature and ATEX-certified?
A luminaire is combined certified when it meets both the requirements for explosion-proof lighting (ATEX Directive) if validated for use in extreme ambient temperatures, typically above 60°C or even up to 120°C. This requires two separate engineering paths that converge in the design.
ATEX certification focuses on preventing the ignition of explosive atmospheres by sparks, arcs, or hot surfaces. High-temperature certification focuses on keeping the luminaire functional and safe in extreme ambient heat. A luminaire that meets both requirements must therefore remain explosion-proof even when it is already strongly heated from the outside, which makes the thermal management of internal components considerably more complex.
In practice, this type of fixture is relatively rare. They are specifically developed for environments such as steel mills, foundries, chemical plants, or refineries where heat and explosion risks are simultaneously present. More information about what High-temperature lighting technical content, helps to better understand the complexity of this combination.
Which ATEX zones occur in high temperature environments?
In high-temperature environments, ATEX Zone 1, Zone 2 (for gas atmospheres) and Zone 21 or Zone 22 (for dust atmospheres) mainly occur. The specific zone depends on the frequency and duration for which an explosive atmosphere is present, not on the temperature itself.
Nevertheless, temperature indirectly influences zone classification and luminaire selection. In environments with extreme heat, volatile substances can evaporate more quickly, increasing the likelihood of an explosive atmosphere. Consider chemical processes at elevated temperatures that release solvents or gases, or steel production where dust and heat occur simultaneously.
The most common combinations in heavy industry are:
- Zone 1 with high ambient temperature: Regularly present gas atmosphere, combined with process temperatures above 60°C. Typical in petrochemicals or refineries.
- Zone 2 with infrared radiation: Incidental explosive atmosphere in combination with radiant heat, such as near melting furnaces or foundries.
- Zone 21 of 22 with dust and heat: Combustible dust in combination with high temperatures, such as in certain food processing or pharmaceutical processes at elevated temperatures.
Correctly identifying the zone is a legal obligation and forms the basis for any luminaire selection in a hazardous area.
What are the technical challenges of ATEX lighting in extreme heat?
The biggest technical challenge is thermal management. ATEX fixtures are by definition closed enclosures to prevent sparks or hot surfaces from coming into contact with an explosive atmosphere. But that same closed housing makes it more difficult to dissipate the internally generated heat from the LED driver and light sources, especially when the ambient temperature is already high.
In standard industrial LED lighting, excess heat is dissipated via cooling fins and convection. In an ATEX enclosure, these options are limited. When the ambient temperature also rises to 80°C or higher, the thermal load on the internal components becomes critical. LED drivers and light sources have a maximum junction temperature; if that is exceeded, the lifespan decreases sharply or the fixture fails completely.
Other technical challenges include:
- Material fatigue due to thermal cycling, where the fixture repeatedly heats up and cools down
- Packing and sealing material that must be resistant to both high temperatures and chemical exposure
- Electrical components that must be certified for the specific ATEX category and the ambient temperature
- Limited choice of LED drivers that are both explosion-proof and heat-resistant
- Higher surface temperature of the enclosure which may affect the temperature class of the luminaire
This explains why combined high-temperature ATEX fixtures require custom engineering and cannot be picked from a standard catalog.
How do you choose the right luminaire for a hot ATEX environment?
The selection begins with a precise environmental analysis. You need at least three parameters: the maximum ambient temperature, the ATEX zone, and the explosive substances present (gas, vapor, or dust). Based on these, you determine the required temperature class of the luminaire, the degree of protection, and the explosion group.
Then you go through the following steps:
- Determine the ATEX zone based on the frequency and duration of the explosive atmosphere. This is typically documented in the explosion safety document of the installation.
- Determine the maximum ambient temperature, including peak moments such as during startup or cooling system failures.
- Check the temperature class of the luminaire. The surface temperature of the luminaire must never reach the ignition temperature of the substances present.
- Assess the IP rating in combination with the heat. High IP ratings restrict ventilation, which increases the thermal load.
- Request documentation of tests under combined conditions. An ATEX certificate does not automatically indicate that the luminaire has also been tested at high ambient temperatures.
- Consider maintenance requirementsStrict rules for inspection and replacement apply in ATEX zones. Choose a luminaire whose parts are available and replaceable.
A good lighting expertise is indispensable in this evaluation, because the combination of requirements is rarely fully covered in standard product datasheets.
What does the standard say about combined heat and ATEX applications?
The ATEX Directive (2014/34/EU) determines which luminaires may be used in potentially explosive atmospheres. What the directive does not automatically cover is the performance of that luminaire at extreme ambient temperatures. That combination requires additional validation from the manufacturer.
In concrete terms, this means that an ATEX-certified luminaire always has a specified ambient temperature range, expressed as Ta (ambient temperature). Most standard ATEX luminaires are certified for a Ta of up to 40°C or 55°C. When the ambient temperature is higher, the luminaire is operating outside its certified range and loses its ATEX validity.
For applications above the standard Ta values, a specifically certified luminaire is required, in which the manufacturer demonstrates that all ATEX requirements are met even at those higher temperatures. This requires additional testing and documentation that are separate from the basic ATEX certification.
What questions do you ask a high-temperature ATEX lighting supplier?
Not every supplier offering ATEX lighting also has experience with high-temperature applications. Asking the right questions helps you quickly distinguish between a specialist and a generalist offering standard products.
In any case, ask the following questions:
- What is the maximum Ta (ambient temperature) for which the luminaire is certified, and was this tested or calculated?
- What is the temperature class of the luminaire, and at what ambient temperature was it determined?
- Has the fixture been tested under combined loading (heat and ATEX conditions simultaneously)?
- Which materials are used for seals and housing, and what is their behavior under long-term exposure to heat?
- What lifespan expectancy does the supplier use at the maximum Ta?
- What are the maintenance requirements in ATEX zones, and does the supplier also provide documentation for this?
- Are there any reference projects with similar conditions?
A supplier who can answer these questions directly and concretely shows that they truly understand the subject matter and are not just selling a product.
Practical example: High-Temperature Industry at Rockwool
A striking example of combined lighting challenges is the project at Rockwool, a manufacturer of stone wool insulation material. In these types of production environments, extreme temperatures are no exception: the production process takes place at temperatures that standard industrial lighting simply cannot handle. At the same time, there are dusty environments with specific requirements regarding the safety of the installation.
The technical challenge in this project lay in finding luminaires capable of withstanding intense radiant heat, aggressive dust, and continuous exposure to high ambient temperatures, without maintenance becoming frequent and costly. Standard LED luminaires failed here due to overheating of the driver or degradation of the sealing material.
The chosen solution focused on luminaires with a robust thermal architecture, where the driver is thermally separated from the light source and the housing is resistant to prolonged exposure to heat and dust. The lessons learned from this project confirm the central theme of this article: the combination of heat and explosion or dust safety requires a design that validates both parameters simultaneously, not separately. A luminaire certified only for ATEX offers no guarantee at a 90°C ambient temperature.
More of these types of projects and their technical backgrounds can be found on page about heavy industry and extreme heat.
How JEL Products helps with high temperature ATEX lighting
JEL Products develops and supplies industrial LED lighting for the harshest environments, including applications where high temperatures and explosion safety meet. That is not a standard combination, and JEL Products does not treat it as such.
Specifically, JEL Products offers the following support:
- Technical advice on the correct luminaire selection based on zone, Ta, and present substances
- Fittings such as the Orca and Barracuda, specially designed for extreme temperatures up to 120°C and exposure to infrared radiation
- Guidance on translating explosion safety documents into concrete lighting requirements
- Complete documentation for ATEX applications, including maintenance instructions for certified areas
- Support for the entire process from engineering to commissioning
Do you have a project where high-temperature lighting and explosion safety come together? Get in touch with the JEL Products specialists for a technical conversation without obligations.
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