Casting Light on a Critical Tool

Determining the brightness of a flashlight can confuse even savvy professionals.

• By Fred Fischer
• Feb 01, 2005

A common misconception: All flashlights are created equal.

The truth is they are as different as cars in price, quality, and performance. A flashlight is a sophisticated tool in a professional's arsenal--something that should provide adequate and safe illumination in cold, wet, or otherwise precarious situations. And while off-the-shelf flashlights are often sufficient for the task at hand, there are numerous occasions in which they are simply inadequate: extreme weather conditions; environments that contain flammable gases; and situations that demand a special quality of lighting, sterilization after use, or just plain good light.

Advances during the past decade have resulted in a palette of technologically sophisticated flashlights. Here's a quick look at criteria for selecting the flashlight best suited for you and your associates.

A Flashlight for Every Purpose
When choosing flashlights, first find out how you or your associates will use them. Will they carry them in their hands? Place them in a pocket or holster? Set them on the floor or clip them to a helmet? Do they need to be waterproof or rainproof?

Some professionals need to have their hands free; some need pocket flashlights; others need flashlights that are lightweight. Some will need considerable brightness, while others need only a minimum glow.

For the safety professional buying large quantities of specialized flashlights, it is important to remember you are making an investment. Take the time to analyze these considerations.

Selecting the Perfect Source of Illumination
There are at least six types of flashlight lamps: xenon filled, halogen, vacuum, light emitting diode (LED), high intensity discharge/metal arc (HID), and fluorescent.

Xenon-filled lamps are the industry standard for high-performance lights and boast numerous benefits. They supply bright, white light; won't dim as they age; and provide excellent color rendering (allowing the human eye to easily distinguish very similar colors).

Halogen lamps have similar features to xenon lamps with modest improvements. Vacuum lamps, which dim with age, are the lowest-cost alternatives and often are used in inexpensive lights.

Light emitting diode flashlights are extremely durable and last for thousands of hours; they won't break or burn out. LEDs, however, are expensive and can consume a maximum of only five watts of power (not a bright light). Therefore, LEDs are best suited for close-up work.

HID/metal arcs are small bulbs that generate tremendous brightness with the aid of ballast. Ideal for specialty applications, HID/metal arcs are expensive and fragile.

Fluorescent tubes are a good choice for ambient area lighting but have poor color rendering and a weak beam, making them poor choices if a professional needs to see a distant object or distinguish colors.

Candle Power, Lumens, and Watts
Determining the brightness of a flashlight can confuse even savvy professionals. Complicating matters even more, no single measurement reveals the true power of a flashlight. Add in the fact that sellers of flashlights sometimes twist the numbers to make their products appear best, and purchasers are faced with a tough challenge. (See the sidebar, 'Not Your Father's Flashlight.')

Knowing the following terms should help you accurately assess the brightness of a flashlight.

• Candle power: Measures the brightness of the light at the center of the beam but not the overall illumination produced by the light. Safety experts, first responders, and other professionals who require powerful, focused beams need flashlights with high candle power.
• Lumens: Measures the total amount of light released from the bulb. Professionals who need to light up a large area require flashlights with high lumen ratings.
• Watts: Measures the power delivered to the bulb. Watts indicate the energy consumption of the flashlight (the higher the wattage, the greater the battery usage), as well as the total power output.

Another important criterion in evaluating the brightness of a flashlight is beam angle. Spotlights have narrow beam angles, while general-illumination lights have larger angles.

Structurally, the hot center of a light beam is created from the light reflected by the reflector. The outer halo comes from the light rays that missed the reflector and are shined directly outward. Depending on your application, this can be important. A person scanning the contents of a room will want a bright center with a large halo to light up the area. A firefighter, on the other hand, may want a narrow spot beam with no halo to prevent lighting up the surrounding smoke.

In short, read lightings' ratings carefully and, if possible, test a sample light and see for yourself. Remember, a flashlight isn't brighter just because it's larger.

Rating Flashlights for Special Tasks
Some first responders work in environments containing flammable or explosive gases or vapors and therefore need flashlights certified to meet stringent safety requirements.

Three major testing labs certify flashlights in the United States for use in hazardous locations as defined by the National Electrical Code: Underwriters Laboratories (UL), Factory Mutual (FM), and the Mine Safety and Health Administration (MSHA). The Canadian Standards Association (CSA) uses similar criteria as its American counterparts.

Here are the most common location ratings used by these organizations. This will help you to determine the conditions in which a flashlight can be used:

• Division 1: The device can be used where hazardous concentrations of specified flammable gases or vapors exist continuously, intermittently, or periodically under normal operating conditions.
• Division 2: The device can be used where hazardous concentrations of specified flammables exist only under unlikely conditions of operation.
• Class 1: Locations where explosive vapors or gases occur.
• Class 2: Locations where ignitable dust occurs (e.g., grain elevators).
• Class 3: Locations where ignitable fibers and flyings occur (e.g., sewing factories and aluminum powder).
• Groups A, B, C, D, E, F, G: Relates to the actual flammability of the location.
• T Rating: Tells the temperature of the hottest part of the flashlight (relevant when the ignition temperature of the flammable gas is in question).

Plastic vs. Metal: A Question of Usage
Flashlights in plastic casings have numerous benefits. They don't corrode, can't conduct electricity, are chemical resistant, and are ideal in cold environments (a plastic flashlight won't freeze to a first responder's hand; a metal one will). Make sure the housing is thick and sturdy so it can survive the rigors of a demanding environment.

There are significant differences in the plastics used to make flashlights. The least expensive are those made from polyethylene, which often is used to make milk bottles. Professional plastic lights use expensive polymers such as polycarbonate (used to make jet aircraft windshields) and High Impact ABS (difficult to break when dropped). Lights made of these engineering polymers actually cost more to make than machined aluminum lights.

Metal flashlights are sturdier than their plastic counterparts but are generally heavier, which can be a liability in certain situations. They also are prone to corrosion and therefore are poor choices for wet or humid environments.

Batteries and Budgeting for Brightness
There are two reasons to buy a flashlight with rechargeable batteries: to achieve long-term savings by eliminating the cost of disposable batteries, and to power high-wattage lights for high-brightness applications.

There are a number of different types of rechargeable batteries:

• Lead Acid/Starved Electrolyte: The least expensive solution available, lead acid/starved electrolyte batteries have a life of approximately 200 cycles. They must be recharged after each use. If the battery is fully drained and not recharged immediately, it will never again perform optimally. Lead acid/starved electrolyte batteries are quickly being replaced by newer technologies.
• Nickel Cadmium (NiCad): The standard for years, NiCad batteries last for approximately 500 to 1,000 charges but are more expensive than lead acid/starved electrolyte batteries.
• Nickel Metal Hydride (NiMH): Offering 1.6 times more capacity than NiCads, NiMH batteries are gaining in popularity. Also, they do not contain cadmium, a hazardous substance damaging to the environment.
• Lithium Ion: The premium battery sold at a premium price, lithium ion batteries offer twice the capacity of NiMH batteries. They cannot be used in hazardous locations, however, due to safety concerns.

Selecting a fast or slow charger is another consideration. Slow chargers take 10 to 12 hours to recharge a battery, while fast chargers take one to two hours. Slow chargers are less expensive than fast chargers, although fast chargers are coming down in price.

Here's a simple way to determine whether your team needs a fast or slow charger: If the flashlight can be recharged overnight, a slow charger is an appropriate choice. If first responders are using flashlights frequently and on demand, a fast charger is better suited to the task.

Selecting the appropriate disposable battery also can pose challenges. The following descriptions should help you select the one ideal for your use:

• Alkaline: The least expensive but still the best choice, they have a good shelf life (up to five years) when stored in a cool area and work when you need them. The downside is that they do not perform well in the cold and can leak on occasion, causing damage to the flashlight. When using them, always observe any polarity label, never mix brands or ages, and store batteries outside of the flashlight.
• Lithium Iron Sulfide (FeS₂): An expensive, long-lasting battery, lithium FeS₂ is a good choice for teams that don't have the time to replace batteries frequently.
• Lithium Magnesium Dioxide (MnO₂): A powerful, lightweight battery, lithium MnO₂ batteries perform much better in the cold than alkalines but cost considerably more. They also can supply greater current than alkalines and drive higher-wattage lamps.

Spectral Issues
Professionals may require flashlights that emit special colors of light. Examples of tasks that require this include searching for blood, checking for counterfeit money, night vision equipment illumination, and evaluating the coloration of dyes and paints.

Contrary to popular belief, LEDs are not smart choices for professionals who have to distinguish things such as a victim's skin color or color coding in a wire bundle; colors do not appear vividly under an LED's lights. Xenon and halogen bulbs are the best choices.

Color temperature and color rendering are two criteria manufacturers use to rate flashlights. In general, the higher the rating, the better the flashlight is at illuminating color. And the whiter the light, the easier it is for a first responder to see colors.

Flashlights that generate specialty frequencies--blue, green, red, ultraviolet, and infrared--also are available. These have a variety of uses: looking for markings invisible to the human eye, finding oil leaks, night vision, and so on.

Investing in a Bright Future
Specialty flashlights are an investment in your workforce. They are quality tools that enhance productivity and safety.

Take the time to identify your needs. You may end up paying a little extra up front, but over the long run, you'll have made a smart investment--one that generates the right light for the right application.

Not Your Father's Flashlight

Remember that battered old flashlight in the kitchen drawer, the one whose beam dimmed with age? The days of vacuum flashlights with filaments that grow dim and evaporate have passed. Technological breakthroughs have ushered in a new era of state-of-the-art flashlights, but picking the right one is challenging.

Here are some questions to consider before you make the big purchase:

• Will the flashlight be used to illuminate objects up close or at a distance?
• Will the flashlight be used indoors or outdoors (if outdoors, in what weather conditions)?
• Will the flashlight be used in a safe or hazardous environment?
• Will the first responder need to evaluate color or details, or require general ambient lighting?
• Will the first responder need to have his or her hands free?
• Will the flashlight be on "continuous burn" or be used in short bursts?
• Will the flashlight be used every day or occasionally?

When you've answered these questions, ask the manufacturer for a sample product so you can see whether it works in a real-life setting. Make sure the light is bright enough, the beam is wide enough, and the unit has sufficient battery power for the task at hand.

Only then will you know whether the flashlight meets the needs of your team.

This article appeared in the February 2005 issue of Occupational Health & Safety.

This article originally appeared in the February 2005 issue of Occupational Health & Safety.