How does high humidity combined with heat affect the lighting?

A combination of high humidity and heat affects lighting significantly faster than each of these factors alone. Moisture penetrates fixtures, accelerates oxidation, and causes condensation on electrical components, while heat increases the pressure on materials and seals. For industrial environments where both factors combine, standard lighting is simply not an option. In this article, we answer the most frequently asked questions about this topic.

What happens to lighting when there is a combination of heat and moisture?

When high temperatures combine with high humidity, a double burden is placed on lighting fixtures. Heat causes materials to deteriorate, making seals looser and allowing moisture to more easily penetrate. Once inside, that moisture condenses on cooler components, such as printed circuit boards and connections, resulting in corrosion and short circuits.

Condensation is one of the most underestimated risks in lighting in warm and humid environments. This occurs when a fixture cools down after use, while the ambient air still contains water vapor. The result: droplets of water on the inside of the housing, in direct contact with electrical components.

In addition, heat accelerates chemical reactions, including corrosion. Moisture that would normally cause slow damage does so in a fraction of the time at elevated temperatures. Moreover, for LED lighting, heat shortens the lifespan of the LED driver and the light source itself, especially if the thermal dissipation of the fixture is not designed for extreme conditions.

Why is the combination of heat and humidity more dangerous than each of them alone?

Separately, heat and humidity are already taxing on lighting fixtures. Together, they reinforce each other’s harmful effects in ways that most standard fixtures cannot handle. The core of the problem lies in the interaction between dissipation, condensation, and chemical acceleration.

Heat alone causes thermal stress: materials become brittle and shrink, seals wear out faster, and electronics are subjected to greater strain. Moisture alone leads to slow oxidation and superficial corrosion. But together, they create a cycle that becomes increasingly destructive:

Heat causes the housing to fail, which temporarily makes the seals less effective.
During that expansion, moist air enters.
When cooling, the housing contracts together and the moisture is trapped inside.
Condensation forms on the coldest internal parts.
Elevated temperatures then accelerate the corrosion of those parts.
Electrical connections degrade more quickly, with resulting malfunctions or the risk of fire.

This makes the combination of humidity and heat particularly treacherous: the damage is not always immediately visible, but builds up until it suddenly fails. For High-temperature lighting It is therefore essential that luminaires are specifically designed for this combined load, and not just for one of the two factors.

Which industrial environments are most affected by heat and humidity?

Not every industrial environment is the same. Some sectors are structurally faced with a combination of high temperatures and high humidity, which places specific requirements on the lighting installation.

The most demanding environments include:

Paper mills and pulp industry: Steam processes ensure a consistently high humidity level, while the production environment is also warm. Fixtures above paper machines are exposed to condensing steam and high ambient temperatures at the same time.
Food processing industry: Cleaning processes using hot water and steam, combined with warm production areas, create extreme conditions for lighting.
Harbours and terminals in tropical climates: High outdoor temperatures, along with sea air and high relative humidity, damage fixtures from the outside.
Steel mills and foundries The heat radiation from glowing metal, combined with cool water and steam, makes this one of the toughest environments for lighting.
Climate chambers and test facilities: Although the temperatures here are controlled, the fixtures are deliberately exposed to extreme temperature fluctuations with high humidity.
Offshore and Maritime Environments Salty sea air combined with heat and moisture is particularly aggressive for standard fixtures.

In all these environments, it is true that industrial lighting for humidity and heat It cannot simply be bought off the shelf. The lighting solution must be specifically selected and certified for the relevant conditions.

What do IP ratings mean for lighting in humid and warm environments?

An IP rating (Ingress Protection) indicates how well a luminaire is protected against dust and moisture. The rating consists of two digits: the first represents dust protection, the second water protection. For environments with high humidity and heat, a minimum IP65 is required, but depending on the application, IP66 this IP67 is IP69K necessary.

It is important to understand that an IP rating is determined under standardized test conditions, not under the combined pressure of heat and humidity over a longer period. A fixture with IP65 is resistant to water jets from all directions, but that doesn’t say anything about what happens after years of thermal cycles in a steam-rich environment.

Therefore, the IP rating is a starting point, not an end-all-be-all. Additional factors that should be taken into account are:

The quality of the sealing materials (silicones versus cheaper rubbers)
The thermal resistance of the housing
The presence of a breathing valve to compensate for pressure differences
The corrosion resistance of the material (stainless steel versus aluminum versus plastic)

For a complete overview of what IP ratings mean in practice for your application, the page on IP and IK ratings a clear overview of the different protection classes.

How do you choose the right lighting for environments with high humidity and heat?

The right choice starts with an accurate analysis of the environment. What temperatures are realistic, including outliers? How high is the relative humidity, and is it constant or variable? Are there any aggressive substances present, such as chemicals or salt? The answers to these questions determine which fixture is suitable.

A few practical guidelines for the selection:

Choose fixtures with an IP rating that is appropriate for the worst-case scenario, not the average.
Check that the LED driver is also certified for the relevant temperature range, not just the light source itself.
Ask for the maximum ambient temperature (Ta) that the manufacturer specifies for the fixture.
Choose stainless steel housings or high-quality coated aluminum in corrosive environments.
Consider fixtures with a breathing valve to prevent condensation from forming due to pressure differences.
Ask about the MTBF (mean time between failures) and the warranty conditions in relation to the environment.

In addition to the technical specifications, the installation position is also important. Fixtures exposed to downward moisture or steam require a different mounting solution than fixtures in a side or bottom position. Also consider accessibility for maintenance: in warm and humid environments, regular inspection of seals and connections is essential to prevent malfunctions.

Practical example: VPK Paper

In the paper mills of VPK Paper in Belgium, the temperature in and around the paper machine can in extreme cases reach +120 °C. This is accompanied by steam generation and a very high air humidity within the machine itself. Several previously tried LED solutions did not hold up in this environment. One trial succeeded, after which JEL Products 98 Snapper HT Snapper HT luminaires in AC version were supplied, including light design, engineering, and installation design. At 35 W per luminaire, the installation provides 100 to 200 lux in the machine.

Heat and moisture reinforce each other. Heat shortens the lifespan of LED and driver, and steam and moisture find every weak spot in the seal. In such an environment, the seal is therefore just as crucial as the thermal design. A high IP rating on paper is a start, but matching the interplay of thermal design, material choice, and sealing determines whether a luminaire will continue to work for years under these conditions.

How JEL Products lighting helps with high humidity and heat

JEL Products develops and delivers lighting solutions that are specifically built for the harshest industrial environments, including environments where heat and humidity combine structurally. That starts not with choosing a fixture, but with understanding the environment.

Environmental analysis: JEL Products identifies the specific circumstances, including temperature peaks, humidity levels, and the presence of aggressive substances.
Custom Lighting Design Based on the analysis, an illumination plan is developed that takes into account thermal load per zone and the appropriate choice of luminaires for each location.
Luminaires for extreme conditions: The luminaires by DCbright and DarkLicht are designed for extreme conditions, featuring temperature-resistant housings, high-quality seals, and proven performance in sectors such as the steel industry, paper mills, and offshore environments.
Complete hassle-free service: From engineering and installation to commissioning and maintenance, JEL Products we handle the entire process.
ISO9001 and VCA certified: Quality and safety are guaranteed in every part of the process.

Are you dealing with an environment where humidity and heat challenge the lighting? Then contact us via the JEL Products Contact Page for a no-obligation consultation about the possibilities.

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