LIGHT
Challenge
Electrical power has been lost due to an ice storm, and it is expected to remain off for the next few days. How will your family function at night?
Although not the first thing to come to mind when considering disaster preparedness, light can play a critical role in not only surviving, but also thriving in dangerous situations.
Light serves four basic DP functions:
1. Allows operation in darkness
2. Deters animals and intruders
3. Provides a sense of comfort
4. Interacts with our bodies to maintain good health; helping to create vitamin D, preventing infection, and combating depression
Without light, you are limited to operating only during daylight hours as it is simply too dangerous to work in the dark. How many times have you tried to get up in the night to perform a simple task, only to jam your toe against an unexpected chair or walk nose-first into a door jamb? Imagine how dangerous it would be if you were forced to hike outside into the dead of night to relieve yourself.
For countless years, light has helped people cope with their fears of the dark.
Light has another very real benefit. Having a steady reliable light source allows people to better use their senses, and that helps alleviate the fear that darkness brings. With light, comes a feeling of being in control. Much of survival is keeping the right frame of mind—not melting down. Having a sense of control can help prevent you from making irrational, and perhaps life-threatening, mistakes.
Consider for a moment that about one quarter of the world's population (over 1.6 billion people) lives without electricity and is limited to performing most activities during daylight hours.124 These people know the challenges of trying to function in darkness, and if put in our shoes, could compensate well during this type of crisis. However, the same cannot necessarily be said for the rest of us.
Light comes from a variety of sources, including natural, electrical, fuel-burning, and chemical. Each source has inherent advantages and disadvantages when comparing them by six metrics: intensity, duration, safety, portability, heat output, and energy cost.
Light Source metrics
Intensity
Duration
Safety
Portability
Heat output
Energy cost
The six metrics give you a way to qualitatively compare the suitability of different light sources. There is no one best light source. Rather, you must select a source that best meets the needs specific to your situation. For example, a very bright flashlight that only burns for an hour without a change of batteries would be a logical choice for hiking to safety from a stranded car. Likewise, a fragile gas lantern that emits both heat and light for an entire night would be a better choice for extended home use.
Natural light is light generated by the world around us. This includes sunlight, starlight, and moonlight (i.e., sunlight reflecting off the moon).
Make the most of natural light since it is free in terms of energy cost. Do most of your work during the daylight hours. If you are experiencing a prolonged disaster, use the daytime to prepare for the arrival of nightfall—shoring up shelters, gathering supplies, and seeking out any needed assistance. Whenever possible, evacuation should also be done during the day.
Accomplish as much as possible during daylight hours.
Electrical light is light created by electrical current passing through filaments or solid-state devices. For increased brightness, efficiency, and life, the filaments are sometimes surrounded by special gases (e.g., krypton).
If you have electrical power available, then light is probably not much of a concern. Modern incandescent light bulbs burn for a couple thousand hours each, so even without a single spare bulb in the house it is unlikely that you will be faced with a situation where you are without enough light to function.
Unfortunately, electrical power is often the first utility to fail when a disaster strikes. Without an electrical power source, you are left to use portable light sources that run off of batteries (e.g., lanterns, flashlights) or consume fuel (e.g., candles, lamps, lanterns).
Over the past several years, flashlight technology has advanced significantly with the arrival of high-efficiency white light-emitting diode (LED) bulbs. LED flashlights operate for much longer on a set of batteries than conventional incandescent units, and the LED bulbs never need replacing. The downside is that quality high-output LED flashlights are rather expensive.
There are many good flashlight manufacturers, including Surefire, Pelican, Stream-light, and Maglite. Flashlight intensity can vary anywhere from 5 to over 500 lumens, with most products outputting between 50–115 lumens.125 You should consider a quality flashlight as one of the fundamental pieces of your preparedness gear. Everyone in your family should have his or her own dedicated flashlight. This not only increases their utility, but it also helps alleviate fear.
Select flashlights that are highly visible, such as those decorated with reflective tape and bright colors. This makes them much easier to find when you accidentally misplace them.
Courtesy of Surefire
You will need an adequate supply of batteries for flashlights and electric lanterns. Before stocking up, however, see Chapter 6 for a discussion of battery types.
Recently, so-called “shake lights” were introduced to the flashlight-loving public. These flashlights work on the Faraday principal of generating electrical energy by moving a magnet through an inductive coil. In theory, having a battery-less flashlight sounds fantastic. Simply give the unit a shake, and bright light pours out the end.
Unfortunately, there are several problems with shake lights. First and foremost, many of the flashlights are not very durable—being closer to toys than tools. The second drawback is that the light they generate is neither bright nor long-lasting. The output from shake lights range from 7 to 13 lumens. Compare this to the 140 lumens that a more compact Surefire 9AN re-chargeable LED flashlight emits.
Courtesy of Applied Innovative Technologies
Shake lights require that you physically shake them to store up electrical energy. For example, you might have to shake the flashlight for a minute to get five to ten minutes of light. Also, since they contain a fairly powerful magnet, you must keep them away from sensitive electronics (e.g., laptop computer, cell phone, iPod). They are not good choices for children or the elderly because of the effort required to recharge them. If you plan to purchase a shake light, read reviews to find the better quality choices.126 Applied Innovative Technologies’ Nightstar products are recognized as some of the highest-quality shake lights on the market.
Electric lanterns are used to illuminate wider areas. Nearly all electric lanterns use krypton, fluorescent, or LED bulbs. Each bulb type presents a tradeoff between light output, energy use, and bulb life (see Table 5-1).127
Electric lanterns are powered from batteries (typically D-cells), and some are also equipped with hand cranks—you turn the handle every few minutes to keep it going.
Lanterns are particularly useful in lighting your shelter because they use reflectors to spread the light out rather than focus it as a beam. Electric lanterns don't put out much heat, so they are not good choices to warm up an area. They are however safe (i.e., not a fire hazard), and most models are fairly durable.
Courtesy of Coleman
Since the discovery of fire, people have been burning fuel of one kind or another to produce light and heat. Fuel-based lighting includes bonfires, torches, candles, and oil lamps/lanterns. The big advantage of fuel-burning light is that heat is also produced, thus serving two important needs. Of course, heat may not always be desirable, such as when you are confined to a small shelter in the middle of summer.
Consider carefully the risk of fire when making your light source selection.
There are also several disadvantages to using fuel-burning light sources. They require you to stockpile and handle combustible fuel. This can be dangerous, messy, and smelly. Also, when fuel is burned, fumes and/or smoke may be emitted. However, the most significant drawback to any fuel-burning source is the very real risk of fire that it introduces. Consider this risk carefully when making your light source selection. Introducing additional danger into what is already a hazardous situation means extra care must be taken.
If you have the supplies, a fire can be a great way to generate both light and heat. To safely burn a fire indoors, you must use a fireplace or wood-burning stove with an adequate ventilation system. The burning of wood or any other combustible material releases carbon monoxide, which is deadly if allowed to build up in a room. See Chapter 7 for additional details on indoor heating.
Fires are particularly useful when stuck outdoors and trying to stay warm or cook food. Knowing how to start a fire is one of life's necessities, like learning to swim. For that reason, you should do a bit of research on fire starting. There are countless books, articles, and websites that offer techniques for starting fires. But be warned, actually starting a fire is not the same as reading about how to start a fire! You need to learn about such things as selecting dry tinder, ensuring air flow, and taking advantage of the chimney effect. Someone telling you how to do it won't be enough (which is why I haven't done so here). This is a skill that can only be learned by doing. Once you are ready to test your fire-building skills, hold a class for your family, teaching everyone the basics. It is convenient to combine this class with the “how to use a fire extinguisher” class recommended in Chapter 4.
Candles are the staple of many emergency supply kits. They are inexpensive and burn for many hours. They don't put out much light, but the placement of a few candles in a small room will allow you to function. Some candles even put out enough heat to do very minor cooking (e.g., Nuwick).
There are also lanterns that use candles as their light source, such as Uco's Candlelier and Eastern Mountain Sports’ candle lantern. Candles are simple to use, reliable, and easily stored. However, they introduce a fire hazard, so once again caution is needed.
UCO's Candlelier
Fuel-burning lamps and lanterns are good alternatives to electric lanterns. Their merits are compared in Table 5-2. The distinction between lamps and lanterns is subtle but important. Lamps are kerosene-filled vials topped with a cotton or felt wick inside a glass globe. To adjust the lamp's brightness, you adjust the wick up or down, leaving more or less exposed. Once lit, lamps must remain stationary because the oil can spill, and the wick is very fragile while burning.
Courtesy of BriteLyt
Lanterns are designed to be portable hand-held lights, and are usually equipped with a handle. Fuel-burning lanterns emit both light and heat by expressing flaming gas onto a cloth mantle saturated with a rare earth oxide. As the oxide heats, it emits visible light. Lighting a lantern requires manual pumping to build up the gas pressure, and takes practice to get right. Lanterns that use pressurized propane tanks eliminate the need for pumping.
Table 5-2 Comparing Electric to Fuel-burning Lanterns
|
Electric |
Fuel-burning |
Brightness |
Poor–Fair |
Good–Excellent |
Fire hazard |
No |
Yes |
Emit odors |
No |
Yes |
Durable |
Good |
Poor–Fair |
Nearly all lamps burn kerosene, but lanterns may burn different fuels, including lamp oil, white gas, or propane. Only kerosene or lamp oil should be burned indoors in a lantern. Other fuels emit dangerous levels of carbon monoxide.
Only burn kerosene or lamp oil indoors.
Fuel-burning lamps and lanterns are very good sources of light and modest secondary sources of heat. For convenience, it is a good idea to use a lamp or lantern that burns the same type of fuel as your heating and cooking equipment. Both lamps and lanterns require frequent maintenance, so be sure to keep an ample supply of mantles, chimneys, and wicks.
There are many good choices for lamps and lanterns, including Aladdin, BriteLyt, Coleman, and others. Each has its particular strengths and weaknesses. For example, Aladdin lamps emit a good deal of light, but are expensive and very easy to break. BriteLyt lanterns run on multiple types of fuel and are more durable, but are expensive and can be tricky to operate.
Lamps and lanterns share the same disadvantages as other fuel-burning methods. They introduce a risk of fire, require you to store and handle dangerous fuel, and emit an odor when burning that can be offensive to some people. Because of the fire hazard, you may prefer to use electric versus fuel-burning lanterns when children are present.
Light sticks are a relatively new invention, and are useful for a variety of military as well as commercial purposes. They operate by a chemical process that causes chemiluminescence. The sticks generally contain hydrogen peroxide and color dye inside a plastic sleeve, as well as a glass vial filled with phenyl oxalate ester. When you break the glass vial, a chemical reaction occurs, causing light to be emitted.128
This chemiluminescent process can be accelerated by heating up the light stick. For example, if you put the light stick in boiling water, it will glow very bright. Likewise it can be slowed down by cooling the stick. If you want a light stick to last until the next day, store it in the freezer.
Light stick chemiluminescence process
Since light sticks are waterproof and don't require electricity, you can use them under water as well as in environments where explosives are present. For general DP purposes, light sticks are primarily used for night safety. Each person can wear a light stick, making it easier to keep track of everyone's location without consuming flashlight batteries. Light sticks are not a replacement for flashlights or lanterns. They output only a few lumens and provide merely a soft glow. However, if no other means exists, they can be used as a low-intensity flashlight by cutting open one end of the foil package and allowing light to shine out through the open end.
Light sticks are great for night safety.
Light intensity is an important metric when comparing light sources. Obviously, you want as bright a light as possible; unfortunately there is no single measurement unit to indicate this brightness. Rather, light intensity is reported using several different units, making pre-purchase comparisons difficult. However, with a bit of patience and a dose of math, different light sources can be fairly compared.
Consider this section to be a mathematic aside that is not essential for you to understand when selecting the most appropriate light source. If you feel your eyes glazing over at the sight of equations, simply skip over them and find yourself the brightest flashlight or lantern you can. For those curious about the details of light intensity, read on.
Light is measured in two different ways. One method describes the amount of light actually emitted at the source—defined as radiance. The other method defines the amount of light that illuminates an area some distance away—defined as illuminance.
Radiance is the amount of light emitted from a source and is usually measured in candelas (English units) or lumens (metric units). One candela is roughly the amount of light emitted by a single birthday candle. If the light source emits light in every direction, then you simply multiply the number of candelas by 12.6 to get the number of lumens. More generally, you must know the radiation angle (i.e., the vertex angle of the cone of the flashlight) to convert between candelas and lumens. Below is the equation to convert between lumens and candelas. If you are not a mathematician or engineer, you may need to break out your scientific calculator to apply it.
Table 5-3 Converting Watts to Lumens
Bulb type |
Approx. conversion (watts to lumens) |
Tungsten incandescent |
17 |
Halogen/krypton |
20 |
Compact fluorescent |
70 |
For example, assume you have a flashlight specified as emitting 100 candelas and having a 10° angle of radiance. Converting from candelas to lumens would be done as shown.
Fortunately, lumens have become the norm by retailers of flashlights and lanterns, so it is rare that you will need to convert from candelas.
Electric lanterns that use krypton or fluorescent bulbs are usually specified in watts rather than lumens. There is no direct conversion between watts and lumens because they measure different quantities. Some approximate conversions are given in Table 5-3, and can be used to provide an estimate of equivalent light intensities.129,130,131
For example, a 100-watt incandescent light bulb is roughly equivalent to 1,700 lumens. Likewise, a 13-watt compact fluorescent bulb is equivalent to about 900 lumens.
Illuminance is a measure of how much light falls on a given surface some distance away. It is usually measured in foot-candles (English units) or lux (metric units). The foot-candle is the amount of light a birthday candle shines on a surrounding sphere of one-foot radius. To convert between the two, multiply the number of foot-candles by 10.8 to get the number of lux. No special equations are needed for this one. Thank goodness.
Think of illuminance as how bright an area is. For example, a bright office is lit to about 400 lux, moonlight represents about 1 lux, and midday sunlight might reach as high as 100,000 lux.132
Most of you will probably never need to be numerically rigorous in comparing light sources. The proof is in the pudding—turn the flashlight on in a dark room and see how well it works. For the few who are curious about this sort of thing, you can draw upon these simple terms and conversions.
Light provides both comfort and a measure of safety to your family. It also allows you to function safely and effectively in the dark.
Lighting sources include natural, electrical, fuel-burning, and chemical.
Take advantage of sunlight by accomplishing as much as possible during the day.
When comparing different light sources, consider six metrics: intensity, duration, safety, portability, heat output, and energy cost.
Recent advances in LED technology enable electrical light sources to be very energy efficient.
Fuel-burning light sources are very bright and radiate heat. However, they also introduce a fire hazard.
Fires should never be built indoors without proper ventilation due to the risk of CO poisoning.
Assign a flashlight to every person in your family. Use lanterns (electric or fuel-burning) for wider-area illumination.
Most shake flashlights have questionable durability, limited light output, and short storage duration.
Light sticks can increase night safety, but are not a replacement for flashlights or lanterns.
Portable illumination