How do fluorescent colours work?
Conventional materials absorb visible light energy and reflect visible light energy in the primary wavelength of the colour we see.
Fluorescent materials absorb visible light and invisible ultraviolet light and emit the ultraviolet light at a longer wavelength, making it visible. Fluorescent colours capture our attention because they reflect more light energy than we can observe going into them. This fluorescent phenomenon alerts us in our peripheral vision, drawing our eyes towards the source of the fluorescence.
Fluorescent garments are most powerful in limited light conditions such as dawn and dusk.
For a garment to provide effective protection at night, reflective tape needs to be added.
EN ISO 20471:2013 is an international standard for the safety requirements and test methods of High-Visibility Occupational Clothing. The standard allows for three colours to be used: Yellow, Orange, and Red.
These colours are useful for their brightness and conspicuity against most backgrounds. Conspicuity refers to how noticeable or attention-grabbing a garment is. It is best achieved through colour contrast. This is where a colour appears more striking when against a contrasting background.
Fluorescent yellow is the brightest colour on the chromaticity scale and is the most popular colour for land-based PPE. Though yellow has the greatest luminance, in some situations red or orange might be more conspicuous.
Fluorescent orange is the second colour allowed by EN ISO 20471:2013.
The advantage of orange hi-vis is people’s instinctual association with orange as a hazard identifier. Orange is also the best colour for conspicuity in water and may provide a stronger contrast than yellow on land against green or brown backgrounds. This is partly why orange is so popular in the railway industry. Indeed, Rail Industry Standards (RIS) set a specific target colour rail garments must meet.
The frequent use of orange in road construction signs and cones has made drivers alert to the colour. Hence the frequent use of fluorescent orange clothing for road workers.
^the 3 colours permissible in ISO 20471
Red is the third colour which meets the professional standard EN ISO 20471. Red is less luminous than yellow or orange. However, it is conspicuous against most backgrounds and catches people’s attention as a hazard indicator. We find that fluorescent red is less popular in the UK but very popular in Continental Europe.
Colourific Values Chart
To ensure that we are using EN ISO 20471 compliant fabrics, Leo Workwear map our X and Y chromaticity coordinates on a Colourific Values Chart. We also require a chromaticity report on every batch of high viz fabric we purchase, to confirm that it meets the standards.
Within the three main colours there is scope for quite a lot of variation. For instance, the yellow can range from an almost lime green colour to a bright Saturn yellow much closer to orange.
As you can see in the graph below, the red and orange colour boxes are connected whereas the yellow is a distinct box on the colour range:
This connection is why it is possible that a red colour could fade into the orange box yet still be compliant. If this were the case it would always be noted on the product’s certificate.
The rail orange colour is a defined section within the EN ISO 20471 red-orange colour. All rail garments must be within the RIS-3279-TOM rail orange coordinates as received but are permitted to fade into the larger EN ISO 20471 box after use.
More posts coming soon on non-professional fluorescent colours and the use of hybrid designs.