A Guide to Choosing the Right Light
Basics of Flashlight Bulbs, Batteries and Terms

Flashlight choice depends on intended use.  Typically, there is no one light that works well in all situations.  Consider your applications and the following basic questions:

How Bright? 

Flashlights come with several kinds of bulbs.  The biggest differences are the amount of brightness, longevity of the bulb, runtimes, and the cost.   The following are choices you will encounter:

INCANDESCENT BULB TYPES:

Krypton Bulb – Incandescent bulb filled with Krypton gas.  A very economical bulb, but usually not as bright or long-lived as a xenon or halogen bulb.

Xenon Bulb – Incandescent bulb filled with Xenon gas.  Provides extremely bright, white light.  Xenon bulbs are an excellent choice for long distance performance.

Halogen Bulb – Incandescent gas-filled bulb that blackens less when it ages than other type bulbs. May have longer life than a xenon bulb of equivalent performance.
 
Both xenon and halogen lamps provide high output for their size and a white, natural-appearing light.  Both require periodic replacement and can fail on extreme impact.  They are easily focused and are the most powerful, highest performance, top choices for long distances today.

LED (Light Emitting Diodes) TYPES:

LEDS – A computer chip-like device that emits light when power is applied.  The LED usually has a built-in lens and projects a wider more dispersed light. Their solid-state construction makes LEDs very durable and long-lived – up to 100,000 hours of life.  LEDs do not require periodic replacement as do incandescent lamps.  LEDs are good for close work because of their wide dispersion and soft focus.  Typically, LEDs provide much less power than incandescent lamps but offer the advantages of extremely long runtimes (up to 100’s of hours at low illumination levels) unlike the much shorter runtimes of xenon or halogen lamps.  Safer – solid state lamps make LEDs safer than incandescents in hazardous environments provided  the flashlight has a hazardous location rating.

LEDs come in a variety of color for different applications.  White LEDs are the most popular for general applications.  Which color is right for you?

White – Most popular for all around use. Very close to natural light, which allows you to see “True Color.”
Blue – Extremely bright. Ideal for various industrial and automotive applications and has similar characteristics of a black light.  Also commonly used in forensics.
Green – Extremely bright. Great for Hunters because it preserves night vision and won’t spook game. Also, the International Hunter Education Association (IHEA) teaches students to associate a Green light in the woods as another Hunter.
Red – Ideal for signaling, pest control, and aviation applications. Best at preserving night vision, but does not provide as much usable light as does green.  Insects cannot detect red light and it is ideal for pest control personnel.

Luxeon LEDs – Luxeon LEDs provide the reliability of an LED with the performance of an incandescent bulb and are the latest in high power LED technology on the market today.   Provides a much greater light output than standard LEDs (10X’s brighter) and can be focused with a reflector.  Luxeon LEDs, like standard LEDs, are durable and do not require periodic replacement like incandescent lamps - expected lifetime of a Luxeon LED can be from 10,000 to 50,000 hours.   

Combination LED/Incandescent – LED/Xenon combination lights combine the long run times and durability of LEDs with the brightness of an incandescent.  Arguably, the best of both worlds.

LIGHT MEASUREMENT – TWO BASIC METHODS ARE USED TO RATE LIGHT OUTPUT:       

Candlepower (Peak Beam Candlepower) - A measurement of the brightest spot in the focused beam.  It is a function of both the output of the lamp and the efficiency of the reflector.  The term “candlepower” (now candela) originates from an earlier unit, the “candle,” and was based on an actual candle of specified dimensions and construction.

Lumens (Total Luminous Output) – A measurement of the total light output of the flashlight regardless of beam focus.  It is almost entirely a function of the bulb or LED.

Because the Lumen method does not take into account the focusing efficiency of the reflector, there is no way to convert between the two measurements.

BATTERY CHARACTERISTICS: DISPOSABLE OR RECHARGEABLE?

Disposable batteries, either alkaline or lithium, have excellent storage life, 7 and 10 tears respectively.  They generally offer longer runtimes for a given bulb power and are typically lower in initial purchase price and easier to keep spares on hand.  Their operating costs are considerably higher than rechargeables and they are seldom as bright. Lithium cells have high energy density but are even more costly.

Because rechargeables can be stored in a charger/holder when not in use, they are always ready to deliver full output and full runtime. Rechargeable flashlights using nickel cadmium or lithium ion batteries feature extraordinarily low operating expense and are well suited for frequent use.  They can support a brighter bulb or LED and store conveniently in custom charger holders.  Their initial purchase price is higher but they are more economical to operate over the long run.

THE FOLLOWING ARE BATTERY CHOICES YOU MAY ENCOUNTER:

DISPOSABLE CELLS:

Alkaline - Readily available and fairly cost effective.  However, their performance is affected by, and drops off very quickly, in cold.  They are at their brightest the first time they are used and decline thereafter.  7 year shelf life.

Lithium – Recent price improvements have made these more cost effective, almost rivaling alkalines. They have much better low temperature performance than alkalines.  Their flatter discharge curve maintains high light output longer than alkalines for equal power levels.  10 year shelf life.

RECHARGEABLES:

Nickel Cadmium (or NiCd) – This is the most rugged rechargeable technology and provides the highest performance/cost ratio.  Nickel Cadmiums can be recharged overnight with simple (economical) chargers to keep costs low, or fast charged with more expensive chargers. Good low temperature performance. Rechargeable up to 1000 times. Self-discharges in storage so must be periodically recharged or stored in its charger. Must be recycled or disposed of properly.

Lithium Ion – Delivers the performance of nickel cadmium with about half the size and weight.  Very low self-discharge rate means it can be stored out of its charger.  Good low temperature performance. Rechargeable up to 300 times.  No recycling requirements.

 With the above information on bulb and battery types, you can now ask yourself the following questions to help select the proper light:

Is the work close up or is a long range beam required?

 BATTERY SAFETY:

Always take the following precautions with battery-powered products:

 SAFETY RATINGS:

Any flashlight that will be used in a hazardous environment or confined space should be properly tested to meet or exceed all applicable safety standards for those locations.  When selecting a flashlight, make sure it carries the proper approval ratings.  Choosing the correct light for your application requires a thorough understanding of your working environment, and a realistic expectation of how a properly selected flashlight will operate in those conditions.

The National Electric Code (NEC) defines hazardous locations classifications and protection techniques.  The basic designation is by “class” and “division”.  There are three classes characterized by the type of material present.  Class I locations are made hazardous by presence of flammable gases, liquids or vapors.  Class II locations can be described as hazardous because of the presence of combustible dusts.  Class III locations contain easily ignitable fibers or flyings.  “Division” refers to the likelihood that ignitable concentrations of flammable materials are present in a given area.  Division 1 designates an environment where ignitable concentrations of flammable gases, liquids, vapors or dusts can exist some of the time or all of the time under normal operating conditions or where easily ignitable fibers and flyings are manufactured, handled or used.  Division 2 locations are areas where ignitable concentrations are NOT likely to exist under normal operating conditions or where Class III materials are stored or handled.

This is a simplified explanation of safety approvals and list of some of the conditions for which the approval is valid.  It is not intended as a substitute for a thorough understanding of the subject.  You or the “Authority Having Jurisdiction” is responsible for the proper selection and application, in a properly defined area, of any hazardous locations approved product.  The National Fire Protection Agency (NFPA), the International Electrotechnical Association (IEC) as well as most certifying agencies offering hazardous locations services are helpful references for defining hazardous locations.

GLOSSARY OF TERMS:

The following glossary of terms may also assist in selecting the proper flashlight: 

AMP:  The abbreviation for ampere and amperage.  The unit used to measure electric current
Ampere-hour:  One ampere of current flowing for one hour
Anodizing:  An electro-chemical coating for aluminum.  Hard, durable, and attractive.  Anodized parts are highly corrosion resistant.
ATEX:  European safety rating.  ATEX products are rated for use in or around explosive atmospheres
Bi-Pin Bulb:  A bulb with two contact pins that plug into a socket allowing easy replacement
“Black Dot” Bulb:  The Black Dot prevents stray light and gives the beam the ability to shine through dense mist, fog, and smoke.  Firefighters rely heavily upon this type of bulb for this reason.
CE:  Flashlights carrying this symbol meet applicable European Community Directives and can therefore be sold in Europe
Dual Filament:  A dual filament bulb contains two filaments, which enables users to instantly switch to the second filament when back-up lighting is needed.
EX:  Signifies conformance to European Standards for use in potentially explosive atmospheres
FM:  Factory Mutual Research Corporation is a third-party testing organization that approves products for use in specified hazardous locations.
High Temperature Lens:  Typically made of borosilicate glass, which has low thermal expansion characteristics.  Easy to clean, resists scratching, and has good shock resistance when properly mounted.
Intrinsically Safe:  Not capable of igniting a flammable atmosphere under both normal and “fault” conditions.
Machined Aluminum:  Flashlight components made from this material are lightweight, durable and can be held to tight manufacturing tolerances for superior performance in precision assemblies.
Non-Incendive:  Not capable of igniting a flammable atmosphere under normal operating conditions.
Non-Conductive:  Will not conduct electricity.  Flashlights made with non-conductive case materials protect against electric shock should the flashlight touch an electrical source.
O-Ring:  Used as a gasket to seal the flashlight case against dust and moisture.
Polycarbonate:  Clear, tough, shatterproof, virtually unbreakable polymer used to make the lens in flashlights.  Often hard coated for abrasion resistance.
Pre-focused Lamp Module:  Lamp and reflector furnished and replaced as a unit.  Permanently adjusted for optimum focus.
Reflector:  Surrounds the lamp and directs and focuses the light rays in one direction. 
UL:  Underwriters Laboratories, Inc. is a third-party testing organization that approves products for compliance to electrical specifications and for use in specified hazardous locations.
VOLT:  Unit of electrical potential.  The potential difference between two points in an electrical system is called the voltage between those points.
WATT:  Unit of power.  Electrical power can be calculated by multiplying voltage times amperage