How to buy flashlights
To prevent the filament from oxidizing, it is suspended in an environment devoid of oxygen. Usually, this environment is achieved by surrounding the filament with a glass envelope and replacing the air inside with either a vacuum or an inert gas.
Here are the top things to consider when buying flashlights:
Inert gas type
In recent years, it is the inert gases such as Halogen, Krypton and Xenon inside the glass envelope that have allowed the manufacturers to achieve greater amounts of light output and also allow the filament to burn at higher temperatures. By using these 'classic' gases the results are superior to a simple vacuum lamp as they offer a white collimated beam of light that provides a better tool for professionals such as firefighters. In general terms, Halogen and Krypton would be more powerful than Xenon, but this sentence is not always right. It also depends on many other components and the design of the torch. The difference in the whiteness, or color temperature, between torches is due to the type and quantity of gas inside the glass bulb of each torch.
Another important factor in the making of a professional flashlight is the lamp reflector. The shape and texture of the reflector has a marked effect upon the quality of the beam that is generated by the lamp. Ideally, an efficient reflector should collect all of the light generated by the lamp to create a beam free from shadows and dark rings.
Types of batteries
The batteries used to power flashlights have also evolved over the years, with manufacturers striving to provide the maximum amount of energy inside the smallest container. Torch manufacturers want high voltage and amperage-hour capacity in order to create the brightest and longest lasting torches, and the battery manufacturers have answered the call with new, powerful, primary alkaline and lithium cells, and rechargeable nickel metal hydride (NiMH), sealed lead acid (SLA) and nickel cadmium (nicad) battery packs. With each passing year, the duration of batteries increases while the size of cells shrinks.
Probably the most significant advancement in the field of lighting technology has been the Light Emitting Diode (LED) invented by Nick Holonyak in 1962. This single invention has created a revolution throughout the lighting world. The basic advantages of the LED over Edison's incandescent lamp are greater efficiency of light per watt, lower cost of replacement of the lamp, longer battery life and greater impact resistance. However, due to the relative infancy of the technology, while LED light output is not yet as bright and intense as the current incandescent lamps on the market, money is being poured into this area of research to resolve this shortcoming.
Comparing manufacturers' flashlights
In order to compare professional flashlights, the user should decide which features are most applicable to his work environment. Torches can be compared by reviewing light output characteristics, battery life, manufacturer's guarantees, lamp replacement costs, price and, most importantly for the health and safety market, hazardous location approvals. With respect to the measuring of the light output, manufacturers use Lumens and Lux. Lumens indicate the total amount of light emitted by the light source, whereas Lux measures the intensity of the beam at a distance - itself a function of the reflector. Choosing carefully which torch would better fit a user's expectations means that several manufacturers' torches should be compared for differences in brightness.
Some applications require brightness over all other considerations, and it is here that the incandescent torch reigns. For users requiring highly focused beams, such as firefighters and scuba divers, torches should be examined for beam characteristics and their ability to penetrate the environment in which they are intended to operate.
Portability and usability
By their very nature, all torches are portable. However, market segmentation has forced manufacturers to create lights that match their user's specific requirements, of which portability is an important criteria. Firefighters like to attach the light to their equipment so that they can release it without fear of dropping the torch on to the ground. Look for torches equipped with rings and clips made from durable stainless steel.
Depending on many users' requirements, lighting systems can vary a lot. When a torch needs to operate long hours, it is more efficient, in terms of cost, to use a rechargeable system rather than one with an alkaline primary battery. As firefighters operate in atmospheres with high temperatures, they should select plastic rather than metal torches, in order to avoid the excessive heating of the torch body.
Though they seem to be small and innocuous, the lamp and the batteries inside can be a significant source of ignition when used in a hazardous and volatile environment. The lamp filament operates at a very high temperature and some gases will ignite if they come in contact with either the filament or even the glass envelope. The batteries themselves can be a source of ignition, especially if a short circuit occurs resulting in the generation of a spark. Even the body of a plastic flashlight can build up a significant static-electric charge, and some manufacturers metal plate their lights to prevent such build-ups from occurring.
It is imperative that a torch used by a firefighter or plant maintenance technician operates reliably in the field. The ramification of a flashlight failing at the critical moment when a firefighter enters a burning building needs no explanation.