2009 Flashlight & Worklight Basics “it is important to define what you need lighting for or, to phrase it another way, what you need the light to do, in order to answer the question of which light is best.” Rob Vajko 5/29/2009 www.nationalsafetyinc.com Flashlight & Work light Basics Candlepower, Lumens, Xenon, Luminosity, LED… It can all get pretty confusing. What’s what and what’s best? Well, that all depends on a number of factors. As in most cases, it is important to define what you need lighting for or, to phrase it another way, what you need the light to do, in order to answer the question of which light is best. So we are going to attempt to try to define some terms and try to make sense of the difference available in work lights and flashlights in order to help you make the right choice. To turn a screw you need a screwdriver. To pound nails, you need a hammer. Neither can be used very well to do the job intended for the other. It’s the same with lighting. Defining the terms Candela This measurement of light intensity has been used to replace candlepower since 1948 and is slightly more than candlepower (one candlepower is equal to about 0.981 candela). Strangely enough, you will rarely see lights rated in candela. Candlepower The term “candlepower” though it still shows up on different packages is pretty much obsolete. It was originally defined as the amount of light generated by one candle weighing 1/6th of a pound and burning at a certain rate per hour.1 Thus a flashlight that is rated at 100 candlepower is thought to be a light with the intensity of 100 such candles burning at once. Combination LED/Incandescent This is a bulb that combines LED and Xenon technologies to produce a bulb that has a long running time, that is extremely durable and that is also extremely bright. 1 The rate has been measured in “grains” using different substances from Spermaceti which is a high quality substance that used to be used to make candles. At other times colza oil was used, others used the carbon filament of a electric lamp or the output of a Hefner lamp. For more detailed information on the different ways that candlepower has been measured, see http://en.wikipedia.org/wiki/Candlepower. Page 2 © National Safety, Inc. www.nationalsafetyinc.com Lumens and Candlepower “Lumens” of a “Lumens” of “Peak beam bulb is a LEDs is a candlepower” measurement measurement is a measure of the entire of all the light of the output of the inside the brightest spot bulb. (Focus is “beam angle”. in a focused not beam. considered.) (Taken from the Streamlight website at http://www.streamlight.com/education/guide.aspx) Incandescent Incandescent bulbs are bulbs that are filled with xenon, Krypton or halogen gases. Their primary source of light comes from heat. Most of the light given off, however, is outside the visible spectrum of light which makes it less efficient than other forms of light. • Xenon Bulbs – Filled with Xenon gas. Extremely bright and easily replaceable • Krypton Bulbs – Filled with Krypton gas. Economical but not as bright as other options • Halogen Bulbs – Filled with Halogen gas. Bright, white light. Won’t “Blacken” as much over time as will Xenon and Krypton bulbs. Usually last longer than Xenon bulbs. LED LED stands for “Light‐Emitting Diode”. LED lights do not, unlike incandescent bulbs, heat up. Where incandescent lights loose almost 90% of their energy through heat, LED lights use 70% of the batteries power to produce light. This enables LED lights to burn substantially longer on the same batteries (i.e. if you wanted 100 hours of light you would use 40 batteries for an incandescent bulb and would need to replace the bulb 3‐4 times. For the same 100 hours you might only use 2‐4 batteries and never replace the bulb). Because the bulb isn’t heating up, it never burns out and can last upwards of 100,000 hours. One LED uses only 1/10th of a Watt. Page 3 © National Safety, Inc. www.nationalsafetyinc.com Lumens This is an International System of units (abbreviated “SI” from the French “Le Système International d'Unités“) measurement for the luminous flux of light (See separate definition of “Luminous flux”) Luminous Flux A measurement of light as defined according to the sensitivity of the human eye which perceives light wavelengths differently (see also “radiant flux”) Lux This is an International System of units (abbreviated “SI” from the French “Le Système International d'Unités“) measurement for the intensity of light. It “takes into account the area over which the luminous flux is spread. A flux of 1000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux.” (www.Wikipedia.com) Radiant Flux Also known as “radiant power” the radiant flux is a measurement of the amount of energy or power (measured in light waves) generated by a light source. Unlike Luminous Flux (see “luminous flux”) which measures only light that is visible to the human eye, radiant flux measurement include infrared, ultraviolet and visible light. Page 4 © National Safety, Inc. www.nationalsafetyinc.com The issues that need to be considered in order to pick the correct light. 1. Do I need the light for close up work or to illuminate afar? Some lights, while extremely bright at the source, diffuse quite a bit and don’t project much of a beam. Lights with a deep reflector tend to focus the light beam and provide better illumination over distance. By the same token, if you are working close‐up a flashlight which diffuses the light might be a better choice. 2. Is true color an issue? Certain types of light can actually affect the colors in their beam. Electricians, for example, who need to make sure that they can see the exact color of the wires that they are working on will need to carefully consider the type of light that they use (We also don’t want the bomb disposable teams not being able to see the right color on the wires they are cutting). 3. How long am I going to need the light for? For short, intermittent work, most flashlights will do. If, however, you are going to need to use the flashlight to provide several hours of illumination, you will need to pay close attention to the run time of the flashlight you are purchasing. 4. Will I be using the light in potential explosive environments? If you are going to be working in confined spaces for example, that have the potential for explosive gas build‐up, you will need an intrinsically safe flashlight. An “Intrinsically Safe” flashlight is a light that is completely sealed so that there is no potential for a spark or for heat that might cause an explosion. Hazardous locations are classified by class and division Classes: a. Class 1 – is for locations that are hazardous because of flammable gases, liquids or vapors b. Class 2 – is for locations that are hazardous because of presence of a dust that have the potential to become combustible c. Class 3 – is for locations that are hazardous because of the presence of fibers or flying particles that may ignite. Divisions: A. Division 1 – defines locations where the potential of combustion is present some of the time or all of the time under normal operations. Page 5 © National Safety, Inc. www.nationalsafetyinc.com B. Division 2 – defines locations where the potential of combustion is no likely to be present under normal operations. It is also used to define locations where Class 3 materials are being stored. 5. Do I prefer rechargeable or not? Each one, of course has its’ benefits and drawbacks. With rechargeable flashlights you are out of light when the light dies. With non‐rechargeable flashlights you can simply put fresh batteries in when the light starts to dim. As a general rule rechargeable flashlights are ready to go right from the charger. Non‐ rechargeable flashlights can tend to drain the batteries over time (who hasn’t stumbled around in the dark to find a flashlight during a power outage only to find that the batteries in the flashlight are dead). Over time, the cost of a rechargeable flashlight can be substantial less than that of a non‐rechargeable one. While most rechargeable flashlight cost more upfront, the only cost after that is the price of electricity to change it. Non‐rechargeable flashlights on the other hand incur the cost of batteries to run. That can add up to a substantial difference. Types of power for Flashlights Type of Battery Advantages Drawbacks Disposable Batteries Alkaline ‐ Fairly inexpensive and economical ‐ Affected by heat and cold ‐ Fairly rapid drop‐off when power runs out Lithium ‐ Long shelf life without depleting ‐ More expensive than Alkaline ‐ steady power curve ‐ Affected by heat and cold Rechargeable Batteries Nickel‐Cadmium ‐ High performance ‐ Must be handled properly to avoid (NiCd) ‐ Good value developing memory ‐ Rechargeable up to 1000 times ‐ Not environmentally friendly, must be disposed of properly Lithium Ion ‐ No memory issues ‐ More expensive than standard lithium ‐ Rechargeable up to 1000 times ‐ Easily disposed of ‐ Long run time Lead Acid ‐ Not affected by temperature ‐ Size (they tend to be large) ‐ Long run time ‐ Not environmentally friendly, must be disposed of properly Page 6 © National Safety, Inc.