UNDERSTANDING THE POWER OF UV-C LIGHT

INPAL
Dec 2, 2025
3 min read

When a solar eclipse occurs, the collective feeling is always the same: something changes in the environment. The light dims, the temperature drops a few degrees, and for a moment it seems as if the world has paused. It's not magic. It's modulated radiation.

This cosmic phenomenon serves as a starting point for understanding the power of light, especially when it comes to disinfection. We understand that solar radiation reaches us loaded with visible colors, heat, and also an ultraviolet component, which, although we do not notice it, has a natural microbicide effect.

ECLIPSE AND RADIATION

But here's something curious. Understanding the power of UV-C light, it is more effective at deactivating microorganisms, but natural UV-C light never reaches the Earth. And it is precisely this light that we use artificially.

The sun provides UV radiation, mainly UV-A and UV-B. These wavelengths can damage certain microorganisms and, in open conditions, help to disinfect exposed surfaces... but with limitations:

They are not constant.
They depend on the atmosphere, the time of day, the season, and cloud cover.
They do not enter indoor spaces.

In other words, sunlight is like a natural disinfectant that works when conditions align, but it is not a reliable resource for indoor environments.

UV-C light (especially between 254–265 nm) is extremely efficient at deactivating viruses, bacteria, spores, and mold. It directly breaks down their DNA/RNA, preventing them from reproducing.

The atmosphere blocks almost all natural UV-C, so no indoor space receives this disinfecting effect from the sun. That is why it is artificially recreated inside air conditioning systems and ducts: there we can direct it, measure it, and take advantage of it.

FEATURE	SUNLIGHT (UV-A / UV-B)	ARTIFICIAL UVC LIGHT (254–265 NM)
Antimicrobial effectiveness	Moderate, depending on conditions	Very high, direct action on DNA/RNA
Constancy	Variable	Stable 24/7
Scope	Outside, does not reach interiors	Designed for ducts, coils, and internal chambers
Control	No control	Controllable intensity, time, location, and direction
Disinfection speed	Slow or partial	Fast and repetitive
Risks	Minimum	Only used in enclosed spaces within the air system, isolated from human contact.

COMPARISON BETWEEN SUNLIGHT AND UVC LIGHT IN ACTION

Solar radiation provides certain levels of UV-A and UV-B rays that can reduce microorganisms on exposed surfaces, but its action is limited. The intensity varies depending on the time of day, weather, latitude, and season.

UV-C light, if applied in a controlled and specific manner. It does not illuminate or provide heat; its function is to directly alter the DNA or RNA of viruses, bacteria, and fungi.

Its effectiveness does not depend on external conditions and can be directed exactly to the point where disinfection is required: coils, condensate trays, internal ducts, and also on surfaces.

While solar radiation offers partial and circumstantial disinfection, UV-C provides constant, direct, and highly efficient disinfection, especially in environments where natural light has no effect.

Where we really care about comparing this difference is in air conditioning systems, inside a duct, where not even a ray of sunlight enters. In an air handler and filter. In a wet coil, where darkness is perfect for mold and bacteria to multiply. That's where UV-C radiation does its job.

1. Constant and uniform disinfection

UVC acts while the system is on or off, keeping the air and internal surfaces free of microorganisms.

2. Inactivation of viruses and bacteria in seconds

Unlike the sun, whose action is gradual, UVC attacks the genetic structure of pathogens with each exposure.

3. Less proliferation, less odors

Handling units are damp places. Without disinfection, they become biological colonies. UVC eliminates the cause, not just the symptom.

4. Increased equipment efficiency

When coils are kept free of biofilms, equipment breathes better:

Lower energy consumption
Better heat transfer
Less load on the compressor

5. A barrier that the sun can never overcome

The sun does not penetrate metal, does not enter ducts, does not touch coils. UVC does.

A natural phenomenon such as an eclipse reminds us how a simple change in light can transform an entire environment. UV-C shows us the opposite: how adding the right light, in exactly the right place, can transform the quality of the air we breathe.