For the last 25 years, lighting manufacturers have been in a fierce competition to out-shine each other. The focus of modern manufacturers has been one-upping the next with more lumens from their latest fixture. Specifically, with regard to LED technologies, we saw fixtures in the 10,000 lumen range initially, then 15,000 lumens, 5 or so years ago we saw manufacturers begin advertising light output 20,000 lumens +and more recently, manufacturers are touting 28-30,000 lumens.
When is enough, enough? Does MORE lumens at the source equate to safer firefighters on the fire scene?
Instead of measuring success on whether a product is bigger and brighter, let’s consider that success is meeting specific customer needs with just the right number of lumens to get the job done effectively and safely. I just attended a Fire Apparatus Manufacturers Association event in Arizona (USA) where truck builders and suppliers get together to discuss trends in the industry. One of the presenters, while discussing trade show effectiveness, asked us “imagine you’re a manufacturer of tools; drill bits specifically. When you’re at the show, how do you explain the effectiveness of your product to your customer?” His discussion of the topic explained that instead of focusing solely on making strong or high-quality drill bits, the message was really that your focus is on doing whatever it takes to enable people to drill really good holes. Nobody buys a drill bit because they love drilling; they buy a drill bit because they need to drill a hole in something.
Using that logic, when we speak about lighting, we should be asking the question “What am I trying to accomplish?” And “Do I need to buy the brightest light, or do I need to be able to see the most effective way that allows me to do my job after dark?”
My bet is the latter is more important than the former. Assuming that statement to be accurate, let’s explore some of the practical applications that can help accomplish that job.
1. High quantity with less overall intensity
Often, I am asked “what’s the most important factor to consider when lighting a fire scene?” The answer is not how bright it is, but how consistent the light level is. Think about walking inside a dim office from a bright outdoor location on a summer day: It takes your eyes a few seconds to adjust to the difference in light level. Once adjusted, the lower intensity inside the building ends up being acceptable to work under. The same principle applies at night. If a firefighter near the apparatus goes from an extremely bright area on one side of the rig, through a darker spot, then back to a bright area, their eyes have to work to adjust and compensate for the changing light levels.
By using smaller fixtures spaced more closely around the body of the apparatus, rather than just a few extremely high output fixtures, the adjustment between highs and lows can be reduced. Having a more even light pattern around the apparatus can be one of the most effective changes made in your fleet to improve nighttime visibility. The cost of 4 small fixtures often ends up roughly the same as a fixture with a total cumulative lumen total similar to the full set.
Pictured here are two examples of trucks. The first is a truck with 4x 20,000 lumen scene lights installed midship on the body: one on the rear, and one on the brow edge. The second truck is an example showing 10 smaller fixtures, 8,000 lumens each, spread out around the apparatus. These two set-ups produce similar total volume of light, but the placement of the light on the second truck is easier for the eyes to navigate, reducing the need to adjust to the difference in light intensity, and therefore is clearly advantageous.
2. The COLOR of the light makes a difference
One measurement not often mentioned in the fire service industry is the “Color Temperature” of the light produced by the fixture. Color temperature, in its most simple form, is the measure of how amber/yellow/orange, or how white/blue/purple the light is. Color Temp is measured in Degrees Kelvin (k) on a spectrum. For example, 2800k is typically in the amber color spectrum, while 5,000 is much more “white” and 7000k is blueish or purple.
In modern firefighting, choosing a fixture in the 5-6,000k range is usually a safe choice. However, in some specialty applications a different choice can have a greater impact. Rescue or hazardous materials response apparatus can benefit from a high color temperature. The higher color temperature ~6,000k has a shorter wavelength and reflects off particulate (smoke, steam etc) much better. So for example, in HAZMAT, it is important to know if the railcar you’re working on suddenly vents a cloud of chlorine, or if the pile of spilled oxidizer substance is off gassing and reacting with the environment. High color temperature lighting can help responders see small, or subtle changes faster. Or the lighting color temperature can make those changes more noticeable. Not only can the right choice make the work more efficient; it can literally save lives.
On the other hand, imagine an application like fighting a wildland fire. In these types of fires, dense organic smoke is often collecting in and around the work area. In environments with heavy saturation of particulate in the environment (dusty, smoky environments), using a color temperature with a slightly longer wavelength, 2800-4500k has advantages because the longer wavelength is less prone to reflect back throughout the particulate and blind the operator.
Think about it this way: when the sun rises and sets, the color of the light looks orange. At high noon, the light color looks whiter. One of the reasons our perception of the color changes is that the particles in the lower atmosphere act like a filter that prevents light in the short wavelengths from reaching our eyes. When the sun is directly overhead, the cleaner less dense atmosphere filters less of the spectrum and the more of the white light makes it to our eyes.
Using that principle, imagine if you could only emit light in to a scene that would not get filtered by the particulate in the atmosphere. It would reduce glare, and more of the light emitted from the source would make it to the scene.
a. High color temperature is best in rescue environments where manual dexterity is important
b. Low color temperature is best in environments where dense organic smoke, filled with particulate debris, because it can be used to reduce bounceback and glare
3. Better thermal management yields sustained light output
One factor often overlooked by fire apparatus manufacturers and specifying committees is the ability of the fixture to manage its thermal load. People gravitate towards thin fixtures because they are easier to carry, easier to manipulate and easier to raise on poles/tripods. However, when a cross section of fixtures from the industry is measured, the fixtures that outperform in the long run are those with more thermal mass and a better ability to dissipate heat. Some very popular fixtures get so hot, the measured light output after 30 minutes can be measured with up to 45% degradation.
If you were to take a 150 watt circuit board out of any manufacturer’s fixture, and attach it to the housing of every manufacturer’s fixture, you would notice a significant difference in performance based only on the design of the housing.
How can you ensure you get maximum bang for your buck? Request thermal degradation data from the light manufacturer before you specify it! Or, set the test up in your fire station. Here’s how:
Take a light fixture, plug it in to a known power source, put a light meter on the ground at a pre-set distance from the fixture, and write down the measurements every 5 minutes for an hour. After 1 hour, if the number has stopped dropping, you can consider the fixture “thermally saturated” and calculate the percentage of reduction in output. The number on the meter is less important, but the percentage difference from the highest to the lowest is what’s important.
All fixtures will have some degree of degradation; 15-20% is normal. Anything higher than that indicates a problem with thermal management, which will ultimately reduce the lifespan of the circuit and cause unpredictable light levels on your fire scene.
4. Get the lights up in the air!
When designing a lighting package, one of the common questions asked is “where should I mount the fixtures?” The short answer is, most of the time, as high as possible. Think about the natural shape of the human face: two eyes, symmetrically placed on either side of the skull, recessed back in towards the center of the upper cranium. Humans have eyelids, eye lashes, and eyebrows. If we use this shape to our advantage, those structures on the face can act like the bill of a hat to prevent glare from hitting us directly in the eyes. Elevating the light in the air shining down on the fire scene not only reduces unnatural shadows, but also takes advantage of the natural shape of the human head to keep light out of the eyes of the first responder.
In conclusion, scene lighting can be a complicated topic. If you break it down and adjust your perspective, solve the problem “how do I help my firefighters see at night?” not “how many lumens can I pack in to this space on my apparatus?” If you look at it from this vantage point you are sure to see an improvement in the your crew’s nighttime effectiveness.
For more information, go to www.hivizleds.com