UVB and UVI Measuring Tools

UVB can be a confusing topic. There’s a LOT of information wrapped up in these three letters. But once you understand the difference between UVB and UVI, and what to actually do with these elements in your reptile’s habitat, you’ll feel like a pro! Keep reading to find out just what it is you need to know about UVB and what you need to do with it.

What is UVB?

UVB stands for ultraviolet-B radiation waves. There are also ultraviolet-A waves (UVA) and ultraviolet-C waves (UVC), but we’re not going to worry about those in this article. UVB rays are short-wave radiation and are the rays attributed to sunburns. In reptiles, some UVB rays penetrate the skin and activate vitamin D2 into vitamin D3, which can circulate around the body and be used for different cellular functions. Read more about UVB and vitamin D3 here.

Ultraviolet rays are measured in nanometers (nm) and range from 400 to 200 nm. The decrease in nanometers correlates with a decrease in space between the radiations waves, depicted in the illustration below.

Illustration courtesy of The Repstylist. All Rights Reserved.

What is UVI?

UVI stands for ultraviolet index. This is a unitless measurement developed by Dr. Gary Ferguson, a renowned herpetologist, of the specific UVB waves that contribute to vitamin D synthesis in reptiles. Known as the “Ferguson Zones,” UVI is based on observations of the daytime activities of wild reptile species and the corresponding UVB rays.

Information credit: Dr. Gary Ferguson. Table courtesy of The Repstylist. All Rights Reserved.

UVB and UVI can both be measured. A UVB measurement will provide you with a number between 320 to 290 nm, while a UVI measurement will provide you with a number from 0.0 to 7.0+ (no units). Safe UVI readings correspond to Ferguson Zones from 1 to 4. The difference between UVB and UVI measurements is that the UVI reading is a representation of a collection of information. This number represents the type of daylight exposure (shaded, partial sunlight, or full sunlight) and the corresponding UVB rays that contribute to vitamin D activation.

UVB = Ultraviolet wavelength measurement in nanometers

UVI = Type of sun exposure + corresponding UVB wavelength that activates vitamin D in the body

The fundamental difference between UVB and UVI.

So now that we’ve explained the difference in what you’re measuring with UVB and UVI, how do you measure each of them?

There are a few instruments on the market that will measure UVB and UVI separately. So in order to measure both factors, you’ll need two instruments. Since a UVB measurement does not provide you with information regarding the safety and appropriateness of the UVB related to your specific reptile, we recommend sticking with a UVI measurement.

UVB & UVI Measuring Tools

Meters. Most of the instruments available to measure UVB and UVI are electronic meters. These are small handheld electronic devices that are very easy to operate and read. There are meters that read UVB and meters that read UVI; no meters read both. Meters are great measuring tools because they supply you with an actual value. In terms of UVI, the meters will have a key that will allow you to quickly verify what type of sun exposure your reptile is receiving.

Sensor cards. This tool is the size, shape, and thickness of a credit card, and is used in a similar way to a meter. Again, there is a sensor card that measures UVB and a separate one to measure UVI. The biggest difference between a meter and sensor card is the way the values are presented. Instead of the reading being a number, a sensor card will change color. For UVB, the brightness of the color-changing portion is related to the strength of the UVB. For UVI, the color-changing portion will be one of around 5 colors specific to the different UVI levels. Keep in mind that these colors relate to a range of values; they do not provide an exact UVB or UVI value.

Photo courtesy of Repti Zoo via Amazon.

How to take a measurement:

  1. Hold the device in an upright position.
  2. Place the device in the area you want to measure (let’s say at the basking spot).
  3. Position the sensor piece as close to the area that your reptile can actually access.
  4. Press and hold the button (for meters), allowing the device a few seconds to obtain an accurate reading (just hold in place for a card).
  5. You should measure at the closest spot that your reptile can get to the bulb, and at the ground level to make sure there’s enough of a gradient (decrease) as your reptile moves away from the UVB bulb.
Illustration courtesy of The Repstylist. All Rights Reserved.

As always, if you have any questions about this topic, contact us here or at therepstylist@gmail.com!

©Copyright 2020 The Repstylist. All Rights Reserved.

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