Occasionally I am asked about a flame-resistant garment’s UV (ultraviolet) rating, or the garment’s ability to block UV rays, to protect the wearer from UV exposure. It’s not typical for FR clothing to have a UV rating, but the following will provide some of the basic information about UV ratings.

What is a UV Rating?

A garment’s UV rating is a value called UPF (Ultraviolet Protection Factor). This value is determined by using a spectrophotometer capable of measuring UV transmissions below the visible range, which is from 280 to 318 nanometers. The UPF rating indicates how effective a fabric is at blocking out solar ultraviolet radiation. This testing is performed according to Australian/New Zealand standard AS/NZS4399. UPF ratings range from 15 to 50, with higher ratings indicating more effective blocking and, therefore, better protection for the wearer of a garment made from the fabric. Fabrics that test higher than UPF 50 are rated as UPF 50+.

UPF Ratings and   Protection Categories

UPF Rating

Protection   Category

% UV Radiation Blocked

15, 20

Good

93.3 – 95.9

25, 30, 35

Very Good

96.0 – 97.4

40, 45, 50, 50+

Excellent

97.5 or more

Factors Affecting Fabric UV Protection Levels

There are a number of factors that affect the level of ultraviolet protection provided by a fabric and the UPF rating. In order of importance, these are: weave (tighter is better), color (darker is better), weight (also called mass or cover factor – heavier is better), stretch (less is better) and wetness (dry is better). The other major factor that affects protection is the addition of chemicals such as UV absorbers or UV diffusers during the manufacturing process. These would not normally be used in FR fabrics.

Clothing provides one of the most convenient forms of protection against UV radiation (UVR). All fabrics have some ability to block UVR, but laboratory testing must be performed to determine the effectiveness of different fabrics.

Is there a UPF Rating Requirement?

In the US, although the FDA regulates sunscreens, presently no Federal program exists for sun protective garments. UPF rating of some sportswear designed for outdoor activities is not uncommon, but a UPF rating for FR or non-FR workwear is definitely uncommon. As there are no requirements for a UPF rating and the testing is uncommon and costly, few if any ratings are available for common FR fabrics.

Other UV Considerations

There are a couple of other things you should know about exposing flame-resistant clothing to UV. UV rays can cause a fabric to fade prematurely. How much of an effect this will have depends on the fabric itself, the fabric color, and the types of dyes used. Regardless of the fabric, it will surely tend to fade more quickly with more frequent exposure to the sun.

The other effect that sometimes occurs is the fabric’s loss of strength after continuous exposure. This does not typically affect the FR properties but, if elevated exposure to the sun is expected, you should consult with the FR fabric manufacturers to find out how their fabric holds up to UV.

– Mark