February 25, 2021

A Primer on UVC Light – Part 1, by Dr. David J.

Whatever your take on COVID 19, it has certainly sharpened our focus on contagious disease. As we spiral downwards as a society, it’s a good bet that other contagious disease will be visiting us more often. It is important to remember COVID 19 has not made other diseases fade away, even if the media attention on this virus makes it seem that way. Preppers often focus on bullets, beans and bandages – weapons, stored foods and trauma-related first aid supplies, but realistically disease is probably the main killer in any long-term scenario.

The purpose of this article then, is to get you briefed and up to speed on a type of disinfection called UVC light, that can help prevent contagious disease. “UVC” is an abbreviation for ultraviolet light in the C spectrum and it’s a powerful tool. UVC has a long history of use in disinfection, because it works well and is cost effective. I want you to be able to use it both safely and effectively. In this article I mention a number of UVC products and manufacturers. I have no financial interest in any of them, and they are only included as examples.

Here are some of the things that make UVC unique and useful-

1) It uses much less energy than many of methods of disinfection. Most methods of disinfection require energy to make heat, boil water or steam. UVC just requires enough energy to power a light bulb.

2) There are no chemicals to dry out, spill, or lose potency over time.

3) It can disinfect things that are challenging to disinfect by other means. Like air, paper, fragile or awkwardly shaped items. Air disinfection is of special interest to many as this seems to be the main method of COVID 19 transmission.

4) UVC is an excellent addition in a resource-scarce environment where water and other types of disinfectants are in short supply.

5) It is important to understand that UVC light disinfects, but technically does not sterilize. Complete sterilization, kills all microorganisms and requires high levels of steam, heat or toxic gas. UVC inactivates up to 99.9% of pathogens, but does not technically sterilize. UVC light works by messing with the genetic material of microorganisms, so they cannot reproduce. Once microorganism cannot reproduce, they cannot spread and are rendered harmless.

6) Smell. UVC treated air often has a distinctive smell. Some of the odor is caused by the UVC light interacting with dust in the air. This smell can be distinctive, but is harmless and generally dissipates quickly. The other cause of odor is ozone. When UVC encounters oxygen, it can create ozone. Cheaper, broad-spectrum bulbs create more ozone than do higher quality, narrow-spectrum bulbs. Ozone is a double-edged sword; it neutralizes all manner of microorganism, including ones that are in the shadow of the UVC rays, but it’s also harmful for people to breathe ozone gas.

Some Ultraviolet Light Background

Ultraviolet light is a type of radiation emitted from the sun. It is divided into 3 main categories, A, B, and C based on the light’s wavelength. These categories of light can also be produced by light bulbs. The wavelength is important when purchasing the proper equipment. For our purposes, you want to be sure to purchase products that are in the UVC spectrum, not UVA or UVB. The wavelength of UV light is measured in something called nanometers and is abbreviated as nm.

UVA is the least damaging type of UV radiation. It is the type of UV light that ages our skin. The wavelength of UVA is 315- 400 nm. UVA is not blocked by the atmosphere as it is transmitted by the sun.

UVB light is partially blocked by the atmosphere. UVB light is the type of UV light that causes skin cancer, but also the type of light that our bodies need to make vitamin D. UVB light is used in tanning beds. People who keep reptiles in aquariums are familiar with UVB light, as indoor reptiles need it for their metabolism to stay healthy. The wavelength of UVB is between 280 and 315 nm.

UVC light, the focus of this article, is blocked entirely by the atmosphere on its way from the sun. It is the most dangerous type of UV light.   Life on earth, has little biological defense from UVC, because evolutionarily we were never exposed to it.   The wavelength of UVC light is between 100 and 280 nm, the most effective wavelength of UVC is 254nm. Wavelengths between 100 and 200 nm produce larger amounts of ozone. Try to find bulbs that are close to 254nm.

UVC light is also dangerous to people and animals. Like any powerful tools, it must be used properly. Clothing that blocks the sun, will also block UVC light. Special googles or visors are recommended for eye protection. Conventional eyewear and clear plastic visors, do block some, or maybe even most UVC rays, but I would not depend on them to protect my vision, and recommend specific UVC blocking goggles.

Damage to exposed skin may be slow depending on the part of body exposed and the intensity, but eye damage is very quick and may be long-lasting.   Proper technique and proper protective equipment are essential. Fortunately, it is not complicated or costly to use UVC safely. DO NOT SHINE UVC LIGHT ON UNPROTECTED PEOPLE OR LIVING ANIMALS.

How is UVC used?

UVC light can used the purify air, water, food and hard surfaces. UVC devices can be in ovens, light fixtures, part of air purification systems, wands and certain purpose-built items.

Water – many readers of this blog probably already own a UVC device for disinfecting water. The Steripen and other similar devices found in many bugout/get home bags, uses UVC light to purify water. The bulbs are in a waterproof housing and inserted into the water container for a preset amount of time and turn off when completed. I highly recommend purchasing a UVC water disinfecting device. They are not particularly expensive and work well.

This is good place to discuss a few more characteristics of UVC light

  • It only disinfects what it shines on. Microorganisms in the shadows are not affected. Cloudy water seriously hampers the ability of UVC to completely penetrate through the fluid. Water must be clear for UVC to be effective.
  • It has no effect on chemical contamination. Water treated with UVC may still not be potable due to pesticides and other chemicals.
  • Distance, time and strength. Some microorganisms are neutralized quicker than others and the strength of UVC light falls off with distance (more on this later). The manufacturers of these devices base the run time on the size of the expected container, (The larger the container, the greater distance that the light must travel) and the most likely pathogens in the water. When in doubt, run it twice.
  • The strength of the light is influenced by the voltage of the batteries and the condition of the bulb. If using older batteries or bulbs, exercise caution.
  • Plastics and glass absorb UVC and greatly diminish or stop its transmission, that’s why it’s safe to hold the bottle when running the device. It is possible to use a wand-type UVC device to disinfect an open basin of water by running the wand over the surface and not immersing, but the basin must be fairly shallow and allow for light transmission. Shining a handheld device on the outside of a bottle would not be effective.
  • Over time, UVC will break down plastics and fabrics, the same way sunlight will.

(To be concluded tomorrow, in Part 2.)

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